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dissertation entitled

SYNTHESIS AND MODIFICATION OF PORPHYRIN, PORPHYRINONE
AND BENZOCHLORIN DERIVATIVES AS PHOTOSENSITIZERS FOR
PHOTODYNAMIC THERAPY

presented by

Sangwan Lee

has been accepted towards fulfillment
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SYNTHESIS AND MODIFICATION or PORPHYRIN, PORPHYRINONE
AND BENZOCHLORIN DERIVATIVES AS PHOTOSENSITIZERS FOR
PHOTODYNAMIC THERAPY
By

Sangwan Lee

A DISSERTATION
Submitted to
Michigan State University
in Partial Fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Chemistry

1995

ABSTRACT

SYNTHESIS AND MODIFICATION OF PORPHYRIN, PORPHYRINONE
AND BENZOCHLORIN DERIVATIVES AS PHOTOSENSITIZERS FOR
PHOTODYNAMIC THERAPY

By

Sangwan Lee '

Photodynamic therapy (PDT) is a very promising therapy and a new
modality for cancer control. This therapy is based on the selective
accumulation of photosensitizing agents in tumor tissues, which activate
oxygen molecule to become cytotoxic species upon irradiation. Especially PDT
based on Photofrin II, a purified form of hematoporphyrin derivative (I-IPD),
is currently in Phase III clinical trials, and the results of the work done so far
with Photofrin II are very favorable and approval of its use for the treatment
of neoplasms has been granted in Canada. However, it is not always clear
which components of the product are responsible for cellular
photosensitization in vivo or in vitra because of the complex nature of HPD.
In addition, I-IPD has weak absorptions in the red region of the visible
spectrum, a region with good tissue penetration. In recent years, using purer
materials, attempts have been made to understand some of the important
parameters for an effective in viva photosensitizer.

To develop second generation photosensitizers for PDT, a series of

structurally related porphyrins, chlorins and bacteriochlorins which have the

tunability of the absortpion maxima covering between 650 to 840 nm have
been synthesized by introduction of oxo group and electron-withdrawing
groups at the ring and by expanding the It-conjugation of the macrocycle.

AS alternatives to Photofrin II, a dimeric porphyrin linked by 6-carbon
chain has been prepared and then transformed to dimeric chlorin and
dimeric benzochlorin to improve absorption in the longer wavelengths.

To study the localization and photodamage mechanism of cationic
photosensitizer in tumor cell, several porphyrin and chlorin derivatives,
which have ammonium group on B-position of pyrrole, and
octaethylbenzochlorin derivatives, which have dimethyliminium group on
mesa position, have been prepared in high yields.

Successful biologic results of these compounds have been obtained and
some biological studies with these compounds, especially the cationic

photosensitizers, are still in progress.

To my family

iv

ACKNOWLEDGEMENTS

I would like to thank Professor C. K. Chang for his guidance, patience
and financial support during the course of this work. I would also like to
thank Professor G. T. Babcock and Professor D. N ocera for serving as members
of my guidance committee. Particularly, I wish to thank Professor G. I.
Karabatsos for serving as the second reader and for always being ready to help.
Financial support from the chemistry department and Michigan State
University is also gratefully acknowledged.

I would like to express my gratitude to the past and present members of
Professor Chang's group - Dr. G. Aviles, Mr. Paul E. Luikart, Ms. Ying Liang,
Mr. James P. kirby, Mr. Craig Shiner, Mr. Guo Baomin and Dr. Nilkamal Bag
for their friendship. Especially, I wish to thank Dr. W. Wu for his helpful
discussions and his kind friendship.

The deepest appreciate is due to my parents, Mr. Deugwoo Lee and Mrs.
500ij Kim as well as my parents-in-law, Mr. Yongsub Son and Mrs. Kyesoon
Park for their love and consistent faith.

Finally, I would like to express my thanks to my wife Myunghee for
her sincere love, encouragement and patience. I am looking for a new life

together with our lovely daughter Kyungmin and son Donghyun.

TABLE OF CONTENTS

Page
LIST OF TABLES .............................................................................................. viii
LIST OF FIGURES ............................................................................................ ix

CHAPTER 1 INTRODUCTION: PORPHYRIN PHOTOSENSITIZATION
AND PHOTODYNAMIC THERAPY

I. GENERAL ...................................................................................... 1
II. SIGNIFICANCE AND BACKGROUND ................................. 3
III. SENSITIZER DELIVERY AND DISTRIBUTION
IN CELLS AND TISSUES ........................................................... 6
IV. THE PHOTODYNAMIC EFFECT ............................................... 8
V. ANIONIC AND NEUTRAL PDT SENSITIZERS .................. 13
VI. CATIONIC PDT SENSITIZERS ................................................. 15
VII. OBJECTIVES OF THE PRESENT WORK ............................... 16
VIII. RESULTS AND PRESENTATION ......................................... 18
D(. NOMENCLATURE ..................................................................... 19

CHAPTER 2 SYNTHESES AND PROPERTIES OF MONO-PORPHYRIN

DERIVATIVES
I. INTRODUCTION ........................................................................ 21
II. SYNTHESES ................................................................................. 24
III. RESULTS AND DISCUSSION .................................................. 31
IV. EXPERIMENTALS ....................................................................... 46

CHAPTER 3 SYNTHESES AND PROPERTIES OF AN IONIC
DI-PORPHYRIN DERIVATIVES

I. INTRODUCTION ........................................................................ 67
II. SYNTHESES ................................................................................. 74
III. RESULTS AND DISCUSSION .................................................. 80
IV. EXPERIMENTALS ....................................................................... 84

CHAPTER 4 SYNTHESES AND PROPERTIES OF CATIONIC
PORPHYRIN AND BENZOCHLORIN DERIVATIVES

I. INTRODUCTION ............................................................................ 97

II. SYNTHESES ...................................................................................... 100

III. RESULTS AND DISCUSSION ...................................................... 117

IV. EXPERIMENTALS ........................................................................... 126
REFERENCES ................................................................................................... 157

Table

LIST OF TABLES

UV-vis absorption spectral data and relative photooxygenation Page
strengh data. .............................................................................................. 41
Photodynamic therapy responses using the RIP tumor. ................. 43
Distribution of porphyrinone (35) in tumor-bearing mice. ............ 4S
UV-vis absorption spectral data of dimeric chloroethylporphyrin

(83), vinylporphyrin (84), formylmethylenylchlorin (85) and
benzoporphyrin (86) in CH2C12. ............................................................ 83

UV-vis absorption spectral data of cationic porphyrin derivatives
containing trimethylammonium group ( 91, 101, 104, 132, 133 and
136) and their precursors (87, 90. 97, 100, 102, 103, 124, 125, 130, 131,
134 and 135). ............................................................................................... 118

In vitra phototoxicity of iminium salts (145, 146, 147 and 148). ..... 125

LIST OF FIGURES

Figure Page
1 Radiative and collisional processes taking place following the
optical excitation of a sensitizer in the presence of oxygen. ............... 10

2 UV-vis absorption spectra of porphyrin (29), 3-porphyrinone (35),
13-porphyrinone (37), and 3,13-porphyrinone (43) in CH2C12. .......... 33

3 UV-vis absorption spectra of porphyrinone (35), 3-dicyanomethide
(45), 3-imine (47), and 3-thione (49) in CHzClz. ..................................... 34

4 UV-vis absorption spectra of 3,13odione (43), 3,13-diimine (51),

and 3,13—dithione (53) in CHzClz. ............................................................. 35
5 Tissue transmittance and photosensitizer absorbance (band I). ........ 37
6 An outline of photolysis system. .............................................................. 40

7 UV-vis absorption spectra of dimeric chloroethylporphyrin (83)
and dimeric vinylporphyrin (84) m C1-12C12. ......................................... 82

8 UV-vis absorption spectra of dimeric chloroethylporphyrin (83)I
dimeric vinylporphyrin (84), dimeric formylmethylenylchlorin
(85) and dimeric benzoporphyrin (86) in CH2C12. ................................. 82

— 9 UV-vis absorption spectra of ImBC (145), NiImBC (146), CuImBC
(147) and ZnImBC (148) in CHzClz. ......................................................... 124

10 UV-vis absorption spectra of SImBC (149), CuSImBC (150) and
ZnSImBC (151) in CHzClz. ........................................................................ 124

CHAPTER 1
INTRODUCTION: PORPHYRIN PHOTOSENSITIZATION
AND PHOTODYNANIC THERAPY

I. GENERAL

Tetrapyrrolic macrocycles are probably the most ubiquitous of all
naturally occuring pigments and include, both heme and chlorophyll. The
first porphyrin isolated was prepared from hemoglobin in 1867. Thudichum1
first prepared this porphyrin by treatment of hemoglobin with concentrated
acid. Four years later, Hoppe-Seyler2 reported a similar preparation and
obtained a purple substance which he called hematoporphyrin (1). About
twenty years later, N encki3 prepared hematoporphyrin hydrochloride (from
isolated hemin) as the first pure porphyrin. However, Schumm and co?
workers4 Showed through spectroscopic investigation that hematoporphyrin
was not the same porphyrin as that of the heme prosthetic group.
Degradative studies by I<iister5 distinguished hematoporphyrin with its
hydroxyethyl side chain from the prosthetic group porphyrin, which
contained vinyl substituents. In 1912, Kiister5 proposed the correct ring
structure (2) for porphyrins.

In 1926 Fischer7 prepared etioporphyrin-I (3) by the first totally
synthetic pathway and followed this shortly thereafter with the complete
synthesis of octamethylporphyrin (4)8 by two distinctly separate methods.

M9

HO
M M9 OH EI Me
Me
Me a
Mo Et

002Me 1 COzMe

This led Fischer to adopt the porphyrin ring structure initially proposed by
Kiister5 in 1912. The extensive porphyrin degradation work and the synthesis
by his group of the four etioporphyrin isomers and twelve of the fifteen
isomers of mesoporphyrin (5, type IX isomer) helped Fischer correlate the
sequence of substituents about the natural porphyrin ring system as the least
symmetrical of the possible fifteen substituent orientations; this was named
as the naturally occurring type D( substituent array, which is related to the
type—III arrangement in circumstances where only two, rather than three,
types of substituent are present. In 1929, Fischer9 synthesized protoporphyrin-
D( (6), and the hemoglobin prosthetic group itself, hemin (7), the iron(III)
chloride complex of protoporphyrin D(.

Me Me Et Me

Me M9 M9 M9

Me Me
4 cozH 5 C02H

 

COzH

6 COZH cozn 7 COZH

Porphyrins and other closely related tetrapyrrolic pigments occur
widely in nature, and are implicated in a great variety of vital biological

processes.

11. SIGNIFICANCE AND BACKGROUND

Certain porphyrins are known to have a photodynamic effect in
mammals; that is, they cause a sensitivity to light which can result in
considerable damage to exposed tissue.10 The reaction requires oxygen, and
there is evidence for the view that singlet oxygen is involved, at least in
certain circumstances.11 The phenomenon was originally observed by
Hausmann12 in mice and by Meyer-Betz13 in man (in himself, actually).
Since the porphyrins are brilliantly fluorescent in UV light (365 nm), this
offers a way of detecting tumors.14:15 The porphyrin preparation in current
clinical use is a product termed HPD (hematoporphyrin derivative) whose
tumor-localizing properties were described over 20 years ago.“ It was not ‘
until 1972 that the two fundamental ideas (localization and photodynamic
effect) came together and the possibility that a porphyrin could be used to

photosensitize the preferential degradation of tumor tissue was
demonstrated.17 Subsequently hematoporphyrin derivative has been shown
to be effective in causing photodegradation of tumor tissue both in
experimental animals and in man.18 The preferential uptake of the
photosensitizers (porphyrins) by tumors and sensitivity to light of tumors
that have taken up a photosensitizer has led to the development of a cancer
therapy called photodynamic therapy (PDT).19'?-5

PDT is a highly promising therapy and a new modality for cancer
control. This therapy is based on the selective accumulation of
photosensitizing agents in tumor tissues,26 which activate dissolved
molecular oxygen to become cytotoxic species27 upon irradiation. PDT with
Photofrin, a photosensitizer made by Quadralogic Technologies, and its
forerunners, hematoporphyrin derivative (HPD) and dihematoporphyrin
ether/ ester (DI-IE), has now been tested in well over 5000 patients world-wide
with encouraging results against tumors in the lung, bladder, esophagus,
skin, and other tissues.28 Especially, PDT based on Photofrin 11,15 a purified
form of HPD, is currently in Phase HI clinical trials,24 and the results of the
work done so far with Photofrin II are very favorable and approval of its use
for the treatment of neoplasms has been granted in Canada. For example,
Kato et al.29 have recently reported that 84% of early stage lung cancer patients
are curable by PDT if the peripheral tumor is less than 2 cm in size and if
metastasis has not yet occured. For early stage, central type lung cancer,
curability increases to 100%.29 In another report, Iocham et al.30 reported that
9 of 15 patients with superficial bladder tumors were still tumor free some 24—
54 months following PDT.

HPD is a complex mixture; although it has been referred to as

"recrystallized",15 it is prepared by precipitation, and proves to be a complex

mixture of porphyrins31 with many investigators not even agreeing on the
definition of the term HPD. Because of the complex nature of HPD, it is not
always clear which components of the product are responsible for cellular
photosensitization in viva or in vitra. The most active component has been
described as a dihematoporphyrin ether, or ester15; however, these were not
available as pure chemicals until Pandey and Dougherty32 synthesized an
ether dimer which was shown to be an effective in viva sensitizer. Red light,
usually from an argon pumped dye laser tuned to 630 nm [corresponding
approximately to the longest wavelength (but weakest) absorption peak of
HPD], is most commonly used in PDT to permit the maximum of light
penetration into mammalian tissue. However, porphyrins absorb poorly in
this region. Thus, there is considerable interest in identifying effective
photosensitizers for PDT that absorb more strongly in the red or near IR
‘ wavelengths to which tissues are highly transparent, and the development of
low-cost reliable diode lasers, which emit in the 750-850 nm range, has
accentuated the need for compounds absorbing around 750 nm (optimum
wavelength for tissue penetration).25

PDT is based on the dye-sensitized photooxidation of biological matter
in the target tissue. In the case of PDT, sensitizers are introduced into the
organism as the first step of treatment. In the second step, the tissue-localized
sensitizer is exposed to light of wavelength appropriate for absorption by the
sensitizer. Through various photophysical pathways, also involving
molecular oxygen, oxygenated products harmful to cell function arise and

eventual tissue destruction results.

III. SENSTTIZER DELIVERY AND DISTRIBUTION IN CELLS AND TISSUES

The first step towards PDT tumor treatment is the delivery of the
photosensitizer to the target tissue. The mechanism of delivery of the active
PDT sensitizers to cells that will ultimately be effected is of great interest as it
may provide insights into the uptake and retention of these compounds in
tumor cells. It has been suggested that HPD may be delivered to tumor cells
by low density lipoprotein (LDL) Since HPD shows a high affinity for LDL and
because tumor cells have increased levels of LDL receptors.33

Lipoproteins are well-known as a vector for cholesterol distribution,
but their role in distribution34 of drugs has only recently been appreciated.
There are three classes of lipoproteins: very low density lipoprotein (VLDL),
low density lipoprotein (LDL), and high density lipoprotein (HDL).35 VLDLS
contain a large percentage of lipids and low percentage of proteins. Therefore,
these substances are very low in density because fats and oils are less dense
than water. In contrast, low density and high density lipoproteins contain
less lipid and more protein and, therefore, are more dense than water. VLDL,
LDL and HDL can be separated by density-gradient ultracentrifugation.

LDL particles ultimately bind to cell-surface receptors. The
predominant circulating lipoprotein species in several animals, notably dog,
mouse rat and horse, is HDL. In contrast, in man, guinea pig and rabbit the
predominant species is LDL. The latter two animals may therefore be good
models for human distribition. In both mouse and man the presence of
neoplastic disease lowers the level of circulating LDL, presumably because of
the high level of LDL receptors in neoplastic tissues. Binding of the various

components of HPD to lipoproteins and serum proteins has been

documented.36 The affinity of several monoporphyrins with serum albumin
has been measured through binding kinetic studies indicating that a major
portion of bound porphyrin is delivered by LDL.33r37 The behavior of VLDL
associated with porphyrin uptake was less clear probably because VLDL is
metabolically converted into other lipoproteins including LDL.

The differences in the behavior of porphyrin-HDL, -LDL and -VLDL
complexes can be explained on the basis of the two main modalities of
lipoprotein internalization by cells. (i) non-specific fluid endocytosis. (ii)
receptor-mediated endocytosis. The latter mechanism concerns LDL and
becomes especially important for cells displaying hyperproliferative activity
where the number of LDL-receptors on the cell surface drastically increase.
Therefore the preferential accumulation and retention of porphyrins by
tumor cells does not seem to reflect an intrinsic property of the dye; rather it
is a consequence of cell-interaction mechanism typical of the LDL. LDL has
been proposed as a specific carrier of cytostatic drugs to tumors.37

Localization of porphyrins in tissue is well documented through
numerous investigations. But the exact mechanism of porphyrin uptake and
retention still remains obscure. The delivery of PDT sensitizers by LDL
suggests a possible mechanism for retention of the active fraction of HPD in
the cell. It is easy to imagine that once through the cell membrane, the
porphyrin-protein complex could break up, during digestion of the
lipoprotein, for example, and that the free porphyrin polymer would then
have poor ability to diffuse out through the cell membrane. Unfortunately
this elegant model has suffered recently because Korbelik and co-workers38
reported that LDL actually inhibits the uptake of Photofrin-II by tumor cells

both in vitra and in viva.

An alternative mechanism for the retention of HPD involves the
tendency of these Species to aggregate in polar environments, such aggregates
might adhere to the outside of the cell wall and be incorporated into the cell
by pinocytosis or nonspecific fluid endocytosis. Once in the internal mileu of
the cell such aggregates could break up and individual molecules could
sequester themselves in lipophilic sites within the cell. I<esse139 provides
some support for this type of model with a study that suggests differing
degrees of aggregation in the oligomeric fraction of HPD as a function of the
polarity of the environment. The real mechanism for the photosensitizer

delivery and distribution in cells and tissues is still obscure.

IV. THE PHOTODYNAMIC EFFECT

The most basic requirement for any molecule to be considered for use
in PDT is that it be a photosensitizer, i.e. capable of absorbing light and
transferring some of the absorbed energy to acceptor molecules. Although
either ultraviolet, visible or near infrared radiation could be possible energy
sources, it is accepted that use of UV-radiafion is disadvantageous, due to both
its poor penetration of tissue12 and the potential for initiating
carcinogenesis.13 Consequently, sensitizers currently being developed absorb
visible light (400-760 nm) or near infrared radiation (760-900 nm).

Similar to ionizing radiation, the damage-initiating step of PDT occurs
within a very small time frame. Photodynamic interactions take place
wherever sensitizer, light of appropriate wavelength and oxygen are present

simultaneously. As shown in Figure 1, once a photon of energy has been

absorbed, the sensitizer is transformed from its ground singlet state (So) to the
excited singlet state (51), and a number of competing processes can occur.
Energy can simply be lost by fluorescence which regenerates the ground
singlet state (So), or by intersystem crossing (ISC) to generate the longer lived
triplet State (T1, lifetime 10'3—10 s) of the sensitizer.

The excited triplet state (T1) can undergo two kinds of reactions and
both processes may generate cytotoxic species.40 It can react directly with
either substrate or solvent by hydrogen atom or electron transfer to form
radicals and radical ions, which after interaction with oxygen can produce
oxygenated products (Type I reaction); or it can transfer its energy to oxygen
directly to form mainly singlet oxygen (102, lifetime 4x10‘5 5 in water, 50-
100x10’6 s in lipid and most organic solvents, 0.6x10‘6 5 in cellular
environment),41r42r43 a highly reactive, oxidative species (type II reaction).44r45
Electron transfer from sensitizer to oxygen molecule can also occur in some
cases, giving oxidized sensitizer and superoxide ion.“6

Strictly speaking, the term "Photodynamic" implies that these transfers
require the involvement of molecular oxygen“7 although this may not be an
absolute requirement for the generation of cytotoxic species in general.
Where oxygen is the acceptor molecule, a number of reactive forms (singlet
oxygen, superoxide anion radical, hydroxyl radical) can be generated. Among
these, singlet oxygen appears to have the longest lifetime and would therefore
seem to be the cytotoxic agent of choice, having the ability to diffuse farther
through the cell and thus increasing the sphere of cell damage.

Since the generation of the triplet state depends on ISC from the excited
singlet state (S1), molecules with high fluorescence quantum yields will

generate lower quantum yields of the triplet state (T1) and consequently, low

COIlC

fluor

10

concentrations of cytotoxic species. Conversely, sensitizers having low

fluorescence quantum yields will generate higher quantum yields of triplet

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Oxygenated
products
ll
02
S Radicals or
1 I Radical Ions
ISC [Type I |
Substrate
or Solvent
”—— (T 1)
02
8 8 I Type II I
1.. a .. .0
Q U U 2
L. 8 5
.8 o “’ Substrate
a Oxygenated,
v: products
.8
a.
So

Figure 1 Radiative and collisional processes taking place following the optical

excitation of a sensitizer in the presence of oxygen.

state (T1) and therefore, higher concentrations of cytotoxic species. Clearly,
this latter situation is more desirable for PDT while the former Situation may

be better suited to in viva imaging of neoplastic tissues.

11

Several indications exist that singlet oxygen (102), formed by energy
exchange with the triplet states (T1) of photosensitizer, is of primary
importance in initiating biological damage, although definitive conclusions
are still lacking.48 Certainly, there can be no doubt that the combination of
oxygen, a photosensitizer, and light of the correct wavelength will generate
singlet oxygen. When this reactive species is created in the vicinity of
oxidizable biomolecules, oxidative damage will assuredly occur. However, it
is not unequivocally shown that such damage will create a cell-killing lesion.
Nevertheless, biological damage is the definitive result of light absorption by
the chromophore, and investigations into the early physical and chemical
events that succeed the photon absorption step are highly relevant within the
context of PDT.

Most sensitizers showing promise in PDT are efficient generators of
singlet oxygen. Since singlet oxygen is 1 eV (22.5 kcal/mol) higher in energy
than the ground state oxygen, the tiplet state (T 1) of sensitizer should have at
least this energy. Extrapolating this back to the energy of the excited singlet
state (51) needed to generate the triplet state (T1) and assuming some energy
loss through other nonradiative processes, it has been suggested that, when
porphyrin based compounds are used as sensitizers, the lowest energy capable
of meeting these requirements translates to an absorption close to 800 nm.“9
Since tissue penetration of light increases with increasing wavelength,so
sensitizers absorbing near 800 nm would be optimum for PDT.

Type I and type 11 reactions may occur simultaneously, and the ratio
between the two processes is highly influenced by sensitizer, substrate and
oxygen concentration, as well as the binding of sensitizer to substrate. There
is much indirect evidence to suggest that singlet oxygen is the major

damaging species in PDT, but direct measurement of singlet production in

COI

inc‘

int-

inc

vi:

ab«

OX'

EX:

for

p9

eff

CO

I19

tm

12

complex biological systems appears to be extremely difficult,51 and most
indirect methods such as the use of chemical quenchers of reactive
intermediates or D20 (which prolongs the singlet oxygen lifetime and so can
increase photosenitization) are not entirely specific for singlet oxygen.“v52'53
In particular, indications are that superoxide ion (02‘) may be involved in
some aspects of PDT damage.54 For Photofrin-II photosensitization of cells in
vitra, full effects are observed at about 5% 02 levels, with a half-value at
about 1% 02. No photosensitization can be observed in the absence of
measurable oxygen. From the above it is evident that PDT effects should be
oxygen-dependent. This is indeed the case for most sensitizers,55 with the
exception of some cationic sensitizers such as the cyanine dye EDKC,55 which
seems to act by oxygen-independent mechanisms.

The measurement of light penetration through tissue is a difficult task
for which mathematical models are still being developed and refined.” light
penetration is also dependent on sensitizer concentration. As sensitizer dose
is increased, a limiting concentration is reached at which sensitizer can
effectively screen out light and thus limit tissue penetration.58 Since this
limiting concentration depends on the effective capture of photons, it would
be expected that sensitizers with larger extinction coefficients would reach a
limiting concentration at lower dose than sensitizers with low extinction
coefficients (assuming similar photodynamic efficiencies).

Progress with regard to drug development will undoubtedely involve
new agents with strong absorbance in the longer wavelengths, with a view

toward promoting eradication of larger tumors. .

13

V. ANIONIC AND NEUTRAL PDT SENSTTIZERS

The products in Photofrin, and most sensitizers in clinical and pre-
clinical trials (benzochlorin derivative, tin etiopurpurin, N -aspartyl chlorin
e6, m-tetrahydroxyphenyl chlorin, zinc phthalocyanine) are anionic or
neutral at physiologic pH, which showed oxygen-dependent PDT effects.

van Lier et a1 .59 reported that in the disulfonated phthalocyanines (8),
the isomer with the acid functions on the same side of the molecule is more
effective than that with the groups on opposite sides of the molecule, which
has been interpreted in terms of the amphiphilic character of the former.

Rodgers et al.60 reported that bis(di-i-butyloctadenyl siloxy)silicon-2,3-
naphthalocyanine (9, isoBoSiNc) is a reasonably efficient photosensitizer
which can be activated with a diode laser at 774 nm. However, isoBoSiNc
suffers from two drawbacks; relatively long skin retention and extreme water

insolubility.

(n’C6Hl3)3SiO

\ \

\ /
$03 '
$03 ' 8

 

14

Cholorophyll derivatives are 7.8-dihydroporphyrins derived from
photosynthetic plants and algae, which possess long wavelength absorption
maxima between 600-700 nm. In plants, chlorophyll-a and chlorophyll-b are
usually present in a ratio of about 3:1. This chemistry is particularly aided by
the commercial availability of Spirulina maxima algae, which contains only
chlorophyll-a. Large amounts of methyl pheopherbide—a can therefore be
obtained,61 which provides access to a large variety of potentially useful
degradation products by way of the " allomerization" reaction. PDT studies
with a series of chlorophyll derivatives are in progress.

Molecules possessing five pyrrole subunits possess interesting long
wavelength absorption bands (22 tt-electron macrocycles). Typical examples of
such 22 tt-electron macrocycles are the pentaphyrin (10)57- and sapphyrin (11)53
systems, whose longest wavelength absorptions are at 682 nm and 678 nm

respectively.

 

15

VI. CATIONIC PDT SENSITIZERS

While singlet oxygen generating, anionic or neutral PDT sensitizers at
physiologic pH are related to the direct cell kill, cationic sensitizers, non-
singlet oxygen generator derivatives, showed the indirect cell kill via vascular
effects.56 Cationic sensitizers could have an advantage, since there have been
reports of selective affinity of such agents for neoplastic cells.“ The
preferential mitochondrial accumulation of cationic sensitizers accounts for
the predominance of mitochondrial damage induced by these dyes.55 Oseroff
and Cincotta66,67 have developed cationic sensitizers, but these compounds
tend to have low extinction coefficients at the longer wavelengths, or need to
be transformed to active sensitizers by intracellular enzymes.

In our search for an effective cationic photosensitizer with strong
absorbance in near-IR, Chang and co-workers68 in studying reversible
modification of formyl peripheral substituents, reported that protonated
imines of ”chlorin-type” compounds are characterized by an unusual red shift
of the absorption maxima to the 800 nm region .

Most recently, Skalkos et (11.69 reported that copper benzochlorin
iminium salts have unusual stability and an unusual red-shift in absorbance
to wavelength as high as 800 nm. Initial photophysical experiments indicate
that the triplet state lifetime of CuBI (copper benzochlorin iminium salt) (12)
is extremely short (<20 nsec) and that singlet oxygen is not produced during
photoactivation.70r71 Hence, CuBI has no tendency to initiate type II
photodynamic activity. Lipid peroxidation of erythrocyte membranes by
photoactivation of CuBI indicate generation of superoxide/ hydrogen peroxide

and that involvement of singlet oxygen is not significant in this experimental

16

model.72 It was known that singlet oxygen generating photosensitizers
disrupt tumor blood flow when measured immediately after irradiation.73
Using the radioactive microsphere technique, it was found that
photoactivation of CuBI formulated in Cremophor EL resulted in decreased
blood flow.70:73

O

12

VII. OBJECTIVES OF THE PRESENT WORK

The principal objective of our study is to develop second generation
photosensitizers for PDT. They should have attractive and chemical
properties including strong absorption maxima at wavelengths where tissues
provide optimal light transmissions, good capacity to generate singlet oxygen
(102) and facile chemical accessibility. In particular, we planned the syntheses
of porphyrins and chlorins which have the tunability of the absorption
maxima covering almost anywhere between 650 to 840 nm, simply by
selecting appropriate substituents at the appropriate positions on the
macrocycle. It is known that porphyrin absorptions can be shifted to longer

wavelengths by expanding the tt-conjugation of the macrocycle and by

17

introducing electron-withdrawing groups at the ring. The following
- categories of compounds are our synthetic targets.
1. Anionic porphflin derivatives.

To increase the tumor localization character, two amphiphilic
porphyrins containing hydrophilic and hydrophobic groups were synthesized.
To achieve strong absorption maxima in the red region of the visible
spectrum where tissues provide optimal light transmissions (thus enabling
treatment of larger tumors and enhancing capacity to generate singlet oxygen,
cytotoxic agent), one or two oxo groups were introduced into the porphyrins
and then transformed to sulfido, imino, and methide groups which are good
auxochromes (bathochromic shift).

As alternatives to photofrin-II, a series of dimeric porphyrins were
prepared for use in PDT. From previous results, a dimeric porphyrin linked
by 6-carbon chain proved to be more effective in viva than others. A dimeric
porphyrin linked by 6-carbon chain was therefore designed and prepared and
then transformed to dimeric chlorin and dimeric benzochlorin to improve
absorption in the longer wavelengths.

2. Qag'onig photosensitizers.

To study the localization and retention mechanism of cationic
lipophilic compound in tumor cell, several porphyrin derivatives, which
have ammonium group on B-position of pyrrole, and octaethylbenzochlorin
derivative, which has dimethyliminium group on mesa position, were
synthesized.

The structural and spectral properties of these compounds have been
characterized by UV-vis, NMR, IR, and Mass spectroscopies. Throughout
these studies, whenever necessary, comparative studies were carried out. For

characterization of these compounds with regard to their stability, biophysical

18

and photophysical properties and pharmacokinetics, including modes of
protein and lipoprotein-mediated distribution, the in vitra tests were done by
Dr. D. Kessel's lab (Department of Pharmacology, Wayne State University
School of Medicine, Detroit, MI 48201), and the in viva tests by Dr. B.
Henderson's lab (Department of Radiation Biology, Roswell Park Cancer
Institute, Buffalo, NY 14263). In addition, the relative photooxygenation

strengths were measured in our lab.

VIII. RESULTS AND PRESENTATION

In this work, 9 kinds of anionic mono-porphyrin derivatives (total; 18)
and a series of anionic dimeric porphyrin derivatives (total; 4) and 7 kinds of
cationic porphyrin derivatives (total; 12) were prepared and sent to Dr. Kessel
for biological tests. Among them, dioctylporphyrinone (15 in Scheme 4)
showed very favorable biological result. Others were too toxic or too non-
toxic to be used in PDT.

To determine the photodynamic efficiency (phototoxicity), the
quantum yield of singlet oxygen molecule (102) production should be
measured. Because the unavailability of some special instruments which
are needed for measuring the 102 quantum yield, the relative
photooxygenation strengths were measured by using dansyl-L-methionine
which was described in chapter 2 in detail.

In this thesis, chapter 2 describes the synthesis of anionic mono-
porphyrin derivatives. To improve absorption maxima in the red region,

some methodologies employed for introduction of "oxo" group and

19

transformation of "oxo" group to sulfido, imino, and methide group are
described in detail. Chapter 3 describes the total synthesis of a dimeric
porphyrin linked by 6-carbon chain and its transformations to vinyl, chlorin,
benzochlorin analogues. In chapter 4, the total syntheses of two kinds of
porphyrins and some structural modifications to obtain cationic analogues
are described. The preparations of mesa-dimethyliminium
octaethylbenzochlorin and its sulfonated analogue from octaethylporphyrin
are also described in detail.

IX. NOMENCLATURE

The parent monocyclic system, pyrrole, is numbered as shown (13).
The Greek letter are sometimes used to distinguish the two types of carbon
position. Two pyrrole rings linked at a a-position to a single carbon function
were named by the Fischer system because the systematic names are tedious
in common use. The macrocyclic system (14) is called porphyrin, a name
originally used (in hematoporphyrin) by Hopper-Seyler.74 The numbering of
ring positions including nitrogen, and the use of letters to denote individual

rings is shown in (14).

53 43- 4 3 3' '
“[350, 50/ \a 3533/ \s.
I” ”I 1'

pyrrole dipyrrylmethane
1 3

 

20

The nomenclature of porphyrinoids with keto group on the ring has
not been standardized. The prefix "oxo", in fact, could be confused with
"oxoporphyrin" or "oxophlorin", which denotes a porphyrin with an oxygen
attached to the methine bridge. Furthermore, we now know that these
ketone derivatives have very little chemical properties in common with
those of the corresponding chlorins or bacteriochlorins. It is probably more
appropriate to consider them "quinones" of porphyrins, hence we propose
the use of "porphyrinone" and "porphyrindione". Sulfido derivatives were
also named as "porphyrinthione" and "porphyrindithione". Other
transformed (irnino and methide) derivatives were named as "chlorins". For
convenience sake, the trivial and systematic names were used whichever is

simpler.

CHAPTER 2
SYNTHESES AND PROPERTIES OF ANIONIC
MONO-PORPHYRIN DERIVATIVES

I. INTRODUCTION

Although Photofrin 11 appears to be an effective photosensitizer, it
shares with HPD the problem of contamination by various porphyrin species
whose contribution to the total biological effect remains unknown. In
addition, both HPD and Photofrin II have weak absorptions in red region of
the visible spectrum, a region with good penetration. In recent years, using
purer materials, attempts have been made to understand some of the
important parameters for an effective in viva photosensitizer. Chlorin
derivatives typically having an intense visible absorption maxima near 640
nm appear to be an attractive system.

Saturation of B-fl' pyrrole double bonds in a porphyrin ring can be
brought about by either reduction or oxidation. Fischer et al.75:75 pioneered
the use of sodium in alcohol to reduced porphyrin to chlorin and this
method has been extended by others77'78 to obtain reduction levels beyond
the chlorin stage, e.g., to bacteriochlorin and isobacteriochlorin. In the
opposite direction, Fischer again was first to study the effect of oxidants on
porphyrin. In the 19305, he reacted porphyrin with hydrogen peroxide in

concentrated sulfuric acid and obtained oxochlorin (porphyrinone)79r80 whose

21

structure was characterized in the 19605.81.82.83 The hydrogen peroxide-
sulfuric acid oxidation of B-Substituted porphyrins result in a complex
mixture of isomeric products containing one, two, and three oxo groups on
the ring with uniformly poor yields.33r34

Recently our group devised a convenient porphyrinone synthesis with
a significantly higher yield by an alternative 2-step reaction via osmium
tetroxide oxidation and acid catalyzed pinacolic rearrangement.85 C. Sotiriou
of our group86 completed a series of experiments aiming to elucidate the
reactivity as well as the migratory aptitude of the biologically important
porphyrin side chains. The results are cited as follows:

1). Relative reactivity of the pyrrole double bond towards
dihydroxylation (via OsO4 oxidation) is highly proportional to, barring
electronic effect, the size of the substituents, the larger the substituent, the
slower the rate. Thus, H = Methyl > Ethyl > -CHzCH2C02R .

2). Migratory aptitude of the substituents is mainly related to their
electronic effects: hydrogen, ethyl, alkyl groups including propionate side
chain will migrate over methyl group and acetate side chain has a lower
mobility than methyl group.

These general rules hold true in most porphyrins.

Most recently, our lab has synthesized another class of porphyrinoid
macrocycles that have desirable absorption characters for use in PDT. These
compounds comprise a porphyrin nucleus containing exocyclic double bond
connecting a B-pyrroline carbon to an oxygen, sulfur, nitrogen, or
electronegative carbon groups (see $c_hgm_g_1_). They are structurally very
similar to natural porphyrins, chemically stable, and synthetically
uncomplicated to prepare. The greatest advantage of this system is the

tunability of the absorption maxima covering between 650-840 nm, simply by

23

selecting appropriate substituents at the appropriate positions on the
macrocycle. At present, the porphyrinone and the porphyrindione, along
with their thione analogues have been proven to be photodynamically active

in vitra .

 

 

o s
5 5\
MeO-<::>el5/ P OMe
\s/S _
N ON
|
NCCHZCN/ Pyridine/1104
NCN

MefiiN=C=NSiMe3 lnq

 

Scheme 1. Syntheses of Sulfido, Imino, and Methide Adducts

24

Since natural porphyrins are very difficult to be converted into specific
structures, we designed an amphiphilic photosensitizer system (29 and 30 in
Scheme 2), primarily to investigate structure-activity relationship for PDT
applications. The porphyrins (29) and (30) can be easily transformed to other
derivatives containing many desirable functional groups which are good
auxochromes (bathochromic shift) as shown in Selim and M. In
addition, the combination of hydrophilic and hydrophobic groups may

increase the tumor localization character.

II. SYNTHESES

As deSCIibed in gheme 2, octanoyl pyrrole (18) and dodecanoyl pyrrole
(19) were prepared from B-free pyrrole (17) quantitatively by acylation with
octanoyl chloride and lauroyl chloride respectively, and then reduced to octyl
pyrrole (20) and dodecyl pyrrole (21) by employing diborane generated from
boron trifluoride etherate and sodium borohydride. Successful results (>
97%) were obtained by using an excess of diborane. The reduced pyrrole (20)
and (21) were separately condensed in 88% formic acid containing 48%
hydrobromic acid to give dioctyl dipyrrylmethene (22) and didodecyl
dipyrrylmethene (23) respectively, which provide the lipophilic character to
porphyrins (29) and (30).

In Scheme 3, benzyl 4-(2-methoxycarbonylethyl)-3,5—dimethylpyrrole-2-
carboxylate (24) was quantitatively transformed by oxidation with lead
tetraacetate to the 5-acetoxymethyl analogue (25), which was condensed in hot
70% aqueous acetic acid to form the dibenzyloxycarbonyl dipyrrylmethane
(26). The benzyl ester groups of the dipyrrylmethane (26) was hydrogenated

 

NlpH
W“ ”m W°\ ‘
O O ACOH O O
15

 

1V

H
Zn, ACOH - I \
H

_. \
\fl/\ NaOMe J 1 7

 

 

o O O'Na"
‘6 it
Such Cn cu
(n.7,11)
o
CnCn Cn
__ ssesncozn 3sz 0"
/\ / / f /\ o-——-— / o
N N 48%l-IBr,A N \ N \
H Br‘ W H o H o
22 n-8 20 n-12 18 "'7
23 n-12 21 n-12 19 "'1‘
002MB COzMO
/ \ T
Br N / N/ Br On On
H - Ht
Br
28

 

 

(1) HC02H(99%). sz
(2) Air-oxidation

M9020 29 n-8 002m
30 nun-12

26

M9020

 

 

Br2/HC02H

COzMe COzMe

Yo /\ Ck/G

N
o H o
25
70% AcOH—HZO
002M. cozm
/ \ / \
31ch N a 00233
H (saxnzcans)
26

27

with 10% palladium/ carbon to give the corresponding diacid (27)
quantitatively. The 5,5’-dicarboxylic acid (27) was brominated to form the 5,5'-
dibromodipyrrylmethene (28), which gives the hydrophilic character to
porphyrins (29) and (30).

As shown in Scheme 2, the dioctyl dipyrrylmethene (22) and the
didodecyl dipyrrylmethene (23) were respectively condensed with the 5,5'-
dibromodipyrrylmethene (28) in anhydrous formic acid in the presence of
one equivalent of bromine to give the dioctylporphyrin (29) and the
didodecylporphyrin (30), which are stable and can be convered to the
porphyrinones (35, 36, 37, 38) and the porphyrindiones (43, 44). In an effort to
synthesize porphyrinones (35, 36, 37, 38) and porphyrindiones (43, 44), as
shown in Scheme 4, we first made vic-dihydroxychlorins (31) and (33) which
were obtained from oxidation of the dioctylporphyrin (29) by osmium
tetroxide. The porphyrin (29) was allowed to react with 1.2 equivalent of
osmium tetroxide in dichloromethane/ pyridine and the reaction was
quenched after 24 hours with hydrogen sulfide to decompose the osmium
ester. In this reaction, the dihydroxylation of porphyrin occured
predominantly at the "northern" pyrrole affording the 2,3-dihydroxychlorin
(31) as the major product along with a small amount of the isomeric 12,13-
dihydroxychlorin (33) which was cyclized to a y-spirolactone derivative
during separation on silica gel chromatography.87 Thus, without isolation of
them, the mixture of vic-dihydroxychlorin (31) and (33) were undergone the
pinacolic rearrangement smothly in acidic medium (usually in concentrated
sulfuric acid or in perchloric acid) to give the 2,7-dioctyl-3-porphyrinone (35)
as the major product along with a small amount of the isomeric porphyrinon

(37). The didodecylporphyrin (30) was also treated with osmium tetroxide

Ch HO Cfl Cn CI!
0.0,
+
29 31 m0 ”“3
the coin. H0020 32mm C02Mo M0023 34a-12 coau-
3Dn-12
H’ H’

 

M002C 430-8
440-12

29

and then with concentrated sulfuric acid in the same way as described above
to yield the 2,7-didodecyl-3-porphyrinon (36) as the major product.

Reaction of the porphyrinone (35) and (36) with 1.2 equivalent of
osmium tetroxide in dichloromethane/ pyridine, followed by treatement with
hydrogen sulfide effected dihydroxylation at the diagonal pyrrole BAT-double
bond of the oxopyrrole without any trace of isobacteriochlorin derivative, to
give vic-dihydroxybacteriochlorins (39) and (40) respectively. This reaction
pattern may be due to the prefered diagonal n-electron delocalization pathway
present in all porphyrins, which prompts the saturation of the diagonal
pyrrole BAT-double bonds with minimum loss of tt-resonance energy.
Without isolation of the vic-diol derivatives (39) and (40), the reaction
mixture was treated with concentrated sulfuric acid to yield the
porphyrindiones (43) and (44) respectively in 40-50% yields. These
porphyrinones (35 and 36) and porphyrindiones (43 and 44) were transformed
to the corresponding dicyanomethylenyl (45 and 46), N-cyanoiminyl (47 and
48), bis(N-cyanoiminyl) (51 and 52), thionyl (49 and 50), dithionyl (53 and 54)
derivatives as shown in Sggme S, to shift their absorption maxima further to
the red region.

In 1984 Aumiiller and Hiiing88 devised a simple, one-step reaction to
produce malonitrile adducts from the corresponding quinones by using
malonitrile, pyridine and titanium tetrachloride. We have applied this
method to the porphyrinones and the diones with good success. Copper(II)
complexes of the porphyrinones (3 5) and (36) were separately treated with
three equivalents of malonitrile in refluxing. chloroform containing two
equivalents of titanuim tetrachloride and an excess amount of pyridine for 30
minutes to yield the dicyanomethylenyl derivatives (45) and (46) respectively
in 44-47% yields, after removal of the copper ion by treatment of the adduct

30

 

 

8 c 0

On n c" c" c" m” On
(3) (2)
W 49 0-8 602". “.0 c 35 0-8 co ". 47 n-8
50 n-12 38 one M'o’c 48 tin-12 coy.
(1)
NO ON
I On
On

M0020 450-8 coau-
450-12

8 Go
On o On On
(3) (2)
s 001’“ O cog“. ucu 002”.

On
H0020 “00:0 51 me
54 n-12 44th 52 M12

 

 

 

(1): i) Cu(OAc)2; ii) (CN)2CHZ, Py, TiCl‘; iii) TFA/st, 20min
(2): i) MgSi—NzC:N—SiMe3. TiCl, 4h, RT ‘
(3): i) Iawesson's reagent, Toluene, reflux, 24h

 

 

 

Sshemsj

31

with hydrogen sulfide in trifluoroacetic acid. The bis-dicyanomethylenyl
derivatives could not be otained because demetallation was impossible by any
acid treatment after condensation with malonitrtle.

Aumiiller and Hiiing39 also reported a convenient conversion of
ketones and p-quinones to the corresponding N -cyanoimine and N,N'-
dicyanoquinonediimine compounds by using bis(trimethylsilyl)-carbodiimide
(Me3Si-N=C=N-SiMe3) with titanuim tetrachloride as auxiliary reagent. The
N-cyanoiminyl (47, 48) and bis(N-cyanoiminyl) (51 and 52) compounds were
easily prepared by treatment of the free base of the porphyrinones (35 and 36)
and the porphyrindiones (43 and 44) respectively with titanium(IV) chloride
and bis(trimethylsilyl)-carbodiimide in dichloromethane at room
temperature. The reactions were completed within 4 hours in 41 -59% yields.

In 1987 Chang and Sotiriou90 reported the synthesis of
octaethylporphyrin (OEP)-thione, dithiones and trithione from the oxo-
analogues by using 2,4-bis(4-methoxyphenyl)-1,3-dithia-2,4-
diphosphosphetane-2,4-disulfide (Lawesson's Reagent). In 1988,
independently, Balch et 111.91 also reported the synthesis of OEP—thione and a
bacteriochlorin-type dithione. The porphyrinones (35 and 36) and the
porphyrindiones (43and 44) were treat with Lawesson's Reagent in refluxing
toluene to give the corresponding thiones (49and 50) and dithiones (53 and
54) respectively in 32-44% yields. '

III. RESULTS AND DISCUSSION

The starting porphyrins (29 and 30) were obtained in ~ 6% yield from
condensation of the dipyrrymethenes (22 or 23) and (28). This low yield is

32

most likely due to the presence of bulky long aliphatic chains (octyl and
dodecyl) which interrupt the cyclization of the two dipyrrylmethenes. The
electronic obsorption spectra of the porphyrins (29 and 30) are exactly same as
that of octaethylporphyrin in the Soret region as well as in the visible region.
The chlorin and bacteriochlorin derivatives have red shifted
absorption spectra (compared to the unreduced porphyrin) as well as
enhanced in viva photosensitizing properties (measured by depth of tumor
necrosis).92 Enhancing long-wavelength absorption was achieved through
oxo-substituted porphyrins which are the pinacol-type rearrangement
products of the diols, and depending on the number and position of the oxo
groups on a porphyrin ring, they can be considered structually derivatives of
chlorin, isobacteriochlorin, or bacteriochlorin. The ketochlorin (35) was
prepared according to Sghgme 4. The intermediate porphyrin (29) was
oxidized with osmium tetroxide to give predominantly the dihydroxychlorin
(31) along with the isomeric chlorin (33). An acid-catalyzed pinacolic
rearrangement was carried out,93 and the principal product (35) was obtained.
The isomeric chlorin (37) was also isolated in trace amounts but its PDT
activities have not been evaluated yet. The didodecylporphyrin (30) Showed
the same reaction results as the dioctylporphyrin (29). The porphyrindione
(43) was only obtained from the porphyrinone (35) by oxidation with osmium
tetroxide and pinacolic rearrangement, and the porphyrindione (44) from the
porphyrinone (36). This reaction pattern may be due to the prefered diagonal
tt-electron delocalization pathway, saturation of the diagonal pyrrole [343'-
double bonds, to minimize loss of n-resonance energy. The presence of the
oxo group generally renders the ring more electronegative and consequently
possessing red-shifted absorption peaks. It was realized that the red-shift can
be greatly enhanced if the oxo group is to be modified into sulfido-, imino-,

 

 

 

 

 

 

 

 

 

 

+1.50n r - - - f
(29)
<253I3.)*
+0.0“ - . 4AA- -
e2.eoa . " r - 4r -
(35)
(2)3?8 ) t)
90.009 , A +LW¢

 

 

 

 

 

 

 

 

*2.509
(37)
(353I3 )
*0.°0“ . M
*2.SOA

 

 

(43)

 

 

 

 

 

 

It I_ In I

" NN
290.9 100.0(NH/DIU.) 800.0
[ 800.0NH 0.00ffi

+0 .000

 

 

Figure .2. UV-vis absorption spectra of porphyrin (29), 3-porphyrinone (35).
13-porphyrinone (37), and 3,13-porphyrinone (43) in CI-IZClz.

 

92.006

(2}3I3.>l

90.00“

(35)

 

 

 

 

 

 

 

 

*2.009

 

t0.009

 

 

 

 

 

 

+1.00“

 

 

 

 

 

 

 

 

 

 

+0.009

4L

 

 

 

200.0

100.0(NH/DIU.)

 

f 800.0NH

0.0015]

Figure 3. UV-vis absorption spectra of porphyrinone (35), 3—dicyanomethide
(45), 3-imine (47), and 3-thione (49) in CHzClg.

 

*2.000 ‘T *

 

 

 

 

 

*0.00A

 

 

92.000

 

 

 

 

00.00A

 

 

*2.009 ' ”ff

 

 

 

 

 

 

+0.00a - I - . I NH
300.0 100.0(HH/OIU.) 800.0
[ 800.0NH 0.00m]

 

 

Figure 4. UV-vis absorption spectra of 3,13—dione (43), 3,13—diimine (51), and
3,13-dithione (53) in CHzClz.

36

and dicyanomethide adducts as shown in Figgre 2~4. These transformations
could be performed with satisfactory yields (35~60%).

The electronic absorption spectra of such adducts are always more
complex than their oxo precursors, displaying multiple bands in the Soret
region as well as in the visible region. While the theoretical interpretation of
these spectral features is still incomplete, the extensive band shifts and
splitting attest to the strong interactions existing between the porphyrin 1r.—
system and the exocyclic double bonds. Qualitatively, changing the number
as well as the relative position of the oxo groups would affect the It more than
the It" orbitals (analogous to the trend: 1t energy of porphyrin < chlorin <
bacteriochlorin). However, addition of tt-electronegative groups would
perturb predominantly the 11:" orbitals. Therefore, with these compounds
there is a great flexibility to modulate the long—wavelength absorption band
which approximates the energy gap between I: and 1t". For the purpose of
PDT applications, the simultaneous red-shift and the increase of the intensity
in the red band(s) appear to be most remarkable

Visible spectroscopy can be a powerful tool in porphyrin chemistry for
detecting changes in the chromophore of the macrocycle. One of the results
of such a change is a shift to higher wavelength of the absorption of band I in
the porphyrin visible spectrum. Because of both lower absorption and low
scattering, tissue transmission is greater at the red end of the visible range
than it is at the blue end, hence the advantage of having photosensitizers
which absorb in the red with a higher molar extinction. Figure 5 illustrates
the point schematically. The attractive absorption characteristics of these new
porphyrinoidal chromophores seems to hold promise. The only potential
complication may be that the sulfide—transforming Lawesson's reagent would

simultaneously convert a carboxylic ester to a thionoester (-CSOR) because

37

2x105
105+ " ”2
8 4- 10-3
I 8
4.1.5
1. ' E
i
.. 10—5 P

 

 

 

 

Figure 5. Tissue transmittance and photosensitizer absorbance (band I).

whi
sim
deli
and
bec
the
The
con

wit

COI‘I

9X3

Cre

llllt
sen
bio
me
rea
mo
sul
me
the
PIN

38

which was detected by mass spectrometer. However, the thioacid is very
similar and can be oxidized to an ordinary carboxylic acid. For drug
delivering purposes, ester groups required prior hydrolysis. Under prolonged
and strong base hydrolytic condition, the cyano group may be hydrolyzed
because small portion of dicyanomethylenylchlorin (45) was turned back to
the parent porphyrinone (35) after the hydrolysis in basic condition.
Therefore the dicyanomethylenylchlorin (45) was hydrolyzed in acidic
condition (in HCOOH containing 5% HQ, overnight, at room temperature)
without any problem. The N-cyanoiminylchlorin (47) was unstable and
turned back to the parent porphyrinone (35) in either acidic or basic hydrolytic
condition. Fortunately ester compound could be solubilized in micells (for
example, by using Tween 80; polyoxyethylene sorbitan monoleate or
Cremophor EL; polyoxyethyleneglycol tr'iricinoleate)94 and injected directly to
animals. As discussed in chapter 1, most of the phototoxicity may be divided
into two major mechanisms95: first, the type I mechanism, in which the
sensitizer molecules excited in the lowest triplet state (T1) react directly with
biological substrates to lead to cell damage, and second, the type II
mechanism, in which the photogenerated triplet state (T1) of the sensitizer
reacts with the oxygen by an energy transfer process to produce singlet
molecular oxygen (102), which in turn reacts with various biological
substrates to injure the biological system. In either type I or type II
mechanism, the photoreaction proceeds via the lowest excited triplet state of
the sensitizer. Therefore, we can reasonably predict that the efficiency of the
photosensitizing damage depends significantly On the lifetime of the lowest

triplet state of the sensitizer.

39

When the type II mechanism predominates, the quantum yield of
singlet molecular oxygen produced from the excited triplet state of the

sensitizer, (D2 is given to be 96’93

<I>2 = ham/(aim + k.)

where ket is the rate constant of the energy transfer from the sensitizer triplet
to oxygen, [302] is the effective concentration of oxygen dissolved in the
medium concerned, and kp is the sum of the radiative and nonradiative
deactivation rate constants for the sensitizer in the triplet state in the absence
of oxygen, being the inverse of the triplet lifetime, kp=1/ 13,.

Accordingly, it is expected that the yield of singlet molecular oxygen is
higher as the rate constant It? is smaller, that is, the triplet lifetime 1:? is
longer. conversely, for compounds with short triplet lifetimes, it is suggested
that the photooxygenation reaction is not apparently phototoxic. Thus, it is
expected that compounds with a triplet lifetime longer than about 100,115 are
useful for PDT, while those with lifetime shorter than about lus are
appropriate as diagnostic agents.96 When heavy metal atom ions such as Fe,
Co, Ni, Mn and Cu ions are introduced into the porphyrin, the decay rate
constant, kp, of the lowest triplet state (T1) increases considerably and the rate
constant in the intersystem crossing process (51-T1) increases simultaneously
because the spin-orbit interaction due to the heavy metal ion is exerted on
both the S1-T1 and the Tl-So processes.99"101 Therefore, free-base (nonmetal)
porphyrins have been used as photosensitizers for PDT.

The photooxygenation ability of the reagents synthesized in this study
was examined as follows: A chloroform solution (2 mL) containing 100 M of

dansyl-L-methionine (d-Met) and 10 [1M of the photosensitizer was irradiated

with a xenon lamp at room temperature with bubbling oxygen gas in the
solution as shown in Figure 6. The reaction mixture was Spotted on a thin-
layer chromatography (TLC) plate (Kodak Chromagram Sheet 13181 silica gel)
with micropipets (VWR 25 pL) every minute, and the TLC plate was
developed in chloroform-methanol (7:3) and observed under a UV lamp ( 365
nm) after development. The reaction end point is represented by the time

(min.) at which the spot of d-Met disappeared on the TLC plate.

 

 

 

 

 

 

 

 

 

‘F—_— 02
xenon lamp
I Iris L. {—
\‘y,’ Ln lens‘ I :3?
K— filter ( > 570 nm)

 

stirrer
Figure 6 An outline of photolysis system

The photooxygenation strength (PS) of a compound is defined as
PS = 10 - (reaction end point)
A greater value of PS means that the photosensitizer possesses higher
photooxygenation properties.102r103 In Table 1, the absorption spectral peaks
of Soret bands and the longest wavelengths and PS are summarized for all
compounds in this study. The photoreactivities are represented by the
relative rates of photooxygenation measured above. The highest rate is
represented by 10 and the lowest by 0. For the sake of comparison, it should
be noted that the rate of photooxygenation is zero for octaethylporphyrin.

41

Table 1 UV-vis absorption spectral data and relative photooxygenation

 

 

 

 

 

 

 

 

 

 

 

strengh data A
[ Absorbance (nm) ]

Compound More“) Mongesda) EP‘” PS“)
29 398 620 8.33 1.67
35 405 641 3.33 6.67
45 459 678 0.83 9.17
47 439 660 1.25 8.75
49 - 457 679 1 9.00
43 409 685 1 9.00
51 448 719 0.42 9.58
53 477 747 0.42 9.58

OEPW 405 620 10 0

 

 

 

 

 

 

 

(a) Agent and Alon est represent Am” at Soret bands and at the longest
wavelength in HzClz,
(b) EP represents the standardized reaction end point. The highest rate
is represented by 10 and the lowest by 0.
(c) PS represents relative photooxygenation strength. PS = 10 - EP
(d) OEP=Octaethylporphyrin.

The biological tests 94:1040f the porphyrin derivatives which have been
carried out by Dr. Kessel and Dr Henderson can be summarized as follows: All
experiments were performed on female C3H/He] mice which, for tumor
response studies, carried the RIF (radiation-induced fibrosarcoma) tumor. All
photosensitizers were dissolved with the aid of Tween 80 (TW80) or
Cremophor EL (CRM) and injected into mice via tail vein. For light delivery,
a 20 Watt argon dye laser system (Spectra Physics) pumping a dye laser using

42

DCM dye (Cooper Lasersonics, Inc., Palo Alto, CA), tuned to 642 nm
(porphyrinone, 35), 660 nm (N-cyanoiminylchlorin, 47), 679 nm
(porphyrinthione, 49) and 685 nm (porphyrindione, 43) by birefringent filter.
In assessment of tumor response, mice were examined at 2-3 day intervals
and the shortest and longest tumor diameters were measured with calipers.
Tumor response was assessed through growth delay analysis as follows. Log
relative tumor volumes (volume after treatment/ volume before treatment)
for the exponentially regrowing tumors were potted against time after
treatment in days. Volumes were calculated from tumor diameters using the
formula for a prolate ellipsoid (LxW2)/ 2, where L is the longest diameter.
The linear portion of the regrowth curve for each tumor was fitted with a
regression line, and the time of tumor regrowth to 10 times its original
(treatment) volume was determined. Tumors were considered cured if no
tumor regrowth occurred by 30 days post treatment. The regrowth rate was
therefore calculated only for animals in which a 30 day cure was not achieved.
In viva/ in vitra (excision) cell survival assay, to assess photosensitization of
RIF rumor cells after in viva exposure to various sensitizers, the latter were
injected and allowed to accumulate in the tumor for 3 or 24 hours. Tumors
were then excised, finely minced and dispersed by an established enzyme
procedure. Two mL aliquots of the single cell suspension were, transferred to
wells of a 24 well tissue culture plate, and exposed to light as described above
for in viva treatment. Following graded does of light, cells were transferred
to 60 mm plastic culture plates for clonogenic assay.

Table 2 shows the tumor response data. Drug does (de)escalation was
started at 4 mole/ kg, dropped to 0.4 mole/ kg if toxicity was observed, and in
the case of porphyrinone(35) back-escalated to 0.8 and 1.6 ,umole/ kg. Light

treatments were carried out generally at 3 and 24 hours after drug injection.

43

Table 2. Photodynamic therapy responses using the RIP tumor.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Drug Light
dose dose Timea n Regrowthb 30day
Sensitizer (umole (I/ cmz) (hour) (days) cures Death
/ kg)

none - - - 10 5.0 (0.3) -— -
none -— 135 - 4 7.8 (0.6) - -
4.0 -- -- 3 6.8 (0.1) - -
Thione (49) 4.0 135 3 4 12.2 (1.7) - '-
4.0 135 24 4 9.6 (1.9) " ‘-

0.4 - - 5 6.7 (0.4) -— - ‘
Irnine (47) 0.4 135 3 12 17.4 (3.6) 4 6
0.4 135 24 10 11.4 (2.2) — '-
0.8 - - 5 6.0 (0.3) "' -'
Porphyrinone 0.4 135 3 7 20.2 (4.3) 1 -
(35) in TW80 0.4 4 135 24 11 12.6 (1.7) - -
0.8 135 3 8 13.5c 7 —

0.8 135 24 5 11.2 (0.4)

Porphyrinone 0.4 135 3 10 15.0 (22) 5 -
(35) in CRM 0.4 135 24 9 11.0 (1.0) 1 -
0.2 - -- 5 6.5 (0.3) "' "'
Dione (43) 0.2 135 3 5 13.7 (1.4) - -
0.2 135 24 4 10.1 (1.0) "' "'

 

(a) Time in hours between injection of sensitizer and light treatment.

(b) Time (days) for tumor regrowth to 10 times the original tumor volume
(average $513). This was calculated only for animals in which a 30 day cure
was not achieved.

(c) Value from one animal only.

In some instances they have tried other intervals, but since no great

improvement of effects were observed, these data are not listed for clarity.

44

The thione (49) was the least effective. The cyanoiminylchlorin (47) was
potent but resulted in a high number of death after treatment (animals
apparently dying of some shock syndrome). The porphyrindione (43) was
also toxic at drug doses higher than 0.2 mole/ kg (only after treatment, not in
the dark), and not very effective at that dose. The porphyrinone (35) was the
best compound of this group, both in TW 80 and CRM, giving high numbers
of cures. The difference between ‘IW 80 and CRM is not significant with this
numbers of animals tested, but CRM may be slightly better. All drugs were
relatively ineffective when light was delivered 24 h after drug injection.

Like the dimeric ketochlorins described in Kessel et al.,105 the
porphyrinone (35) was a very effective short-acting sensitizer against the RIF
tumor in viva , with a significant number of animals tumor-free after 30
days. Because the porphyrinone (35) must be solubilized for injection, the
role of carrier systems in drug biodistribution becomes an important
consideration.

The PDT efficacy of the porphyrinone (35) was correlated with plasma
rather than with tumor concentration of the porphyrinone (35) (Table 2 and
Table 3). Such a result was previously reported for the chlorin
photosensitizer NPe6105 and this was attributed to vascular shut-down, rather
than a direct tumor cell kill during PDT. While the porphyrinone (35) was an
efficacious photosensitizing agent using either vehicle, the number of 30 day
survivors was substantially greater when a 0.4 umol/ kg drug does was
formulated with CRM than with TW 80. This result was associated with a
longer persistence of the sensitizer in plasma and tissues, suggesting that
binding of the sensitizer to a CRM-induced lipoprotein degradation product

plays an important role in the promotion of vascular photosensitization.

45

Table 3. Distribution of porphyrinone (35) in tumor-bearing mice"

 

 

 

 

 

 

 

 

 

 

 

 

CRM TW80
Tissuue 3 h 24 h 3 h 24 h
Plasma 46.94 :i: 2.39 9.97 i 2.14 27.73 i 2.87 4.72 i 0.60
Tumor 3.25 i 0.15 6.69 i 1.25 2.34 i 0.05 3.50 i 0.43
Skin 1.37 i 0.29 2.27 i 0.12 1.28 :l: 0.20 1.46 i 0.18
Liver 19.39 :I: 0.87 22.45 i 2.51 34.84 i 1.27 24.77 i 0.40 i
Muscle 0.91 i 0.07 1.67 i 0.16 0.84 i 0.19 0.84 i 0.05

 

 

" Levels of (35) in RIF tumor and plasma 3 and 24 h after administration
as a function of the drug-delivery vehicle. The compound (35)
concentrations are expressed as mg/ g tissue (wet weight) or mg/mL of
plasma. These values represent the mean :1: SD of three determinations.

It is important to note that blood from many animals used in
preclinical studies, e.g. mouse, rat and dog, exhibit very low levels of LDL,
with the major lipoprotein species represented by HDL.107 The effects of
different drug-delivery vehicles on drug biodistribution in man, where LDL>
HDL, remains to be determined. They interpreted the data presented here to

indicate that choice of delivery vehicle may be as important as the choice of

photosensitizer with regard to the long-term efficacy of PDT.

IV. EXPERIMENTAL

General

Proton NMR spectra were obtained in CDCl3 at 300 MHz (Varian
Gemini 300 FT NMR spectrometer) using TMS or CHC13 (7.24 ppm) as
internal standards. Spectra were mostly recorded in CDC13; the residue CHC13
was used as the internal standard set at 7.24 ppm. Melting points were
measured on an electrothermal melting apparatus and are uncorrected.
Visible absorption spectra were obtained on a Shimatzu UV-160
spectrophotometer using solution in CHzClz. Mass spectral data were
obtained on a Fisons VG TRIO-1 GC-MS mass spectrometer purchased under
a NIH Shared Instrumentation Grant (S10RR06506-01) or a IEOL HX 110-HF
mass spectrometer equipped with a fast atom bombardment (FAB) gun which
purchased under a NIH grant (DRR-00480), for high resolution mass spectra.
Porphyrin-modification reactions were usually carried out in the dark
(aluminium foil) under argon and were monitored using TLC on
commercially available Eastman Kodak 13181 (100 pm thick) silica gel sheets.
Preparative TLC was carried out on 20x20 cm glass plates coated with
Analtech silica gel GF (1000 or 1500 pm thick), and in column
chromatography 200—400 mesh silica gel was used.

Methyl ggximingagetgacetate (15)

Methyl acetotacetate (209 g, 1.8 mol) was dissolved in acetic acid (360
mL) and the solution was cooled in an ice bath. A saturated aqueous solution
of sodium nitrite (138 g, 2 mol) was added dropwise with stirring and the

temperature was controlled below 20 0C. The reaction was continued for

47

another one hour after the addition. The orange oxime solution was kept at

low temperature or used immediately.

'um ~meth l- xobu aldeh de

Sodium methoxide (140 g) suspended in dry diethyl ether (2 L) was
cooled in an ice bath. 2—Butanone (144.3 g, 2 mol) and ethyl formate (148.2 g, 2
mol) were added dropwise for 2-3 hours with stirring and the temperature
was maintained below 20 0C. The reaction was continued for one hour at
room temperature after the addition. After distillation of diethyl ether, the
product was further dried under vaccum. The resulting product was directly
used to prepare (17).

Methyl 4S-Q’methylpmgng-carboxylate (12)

The above oxime solution (1.8 mol) was added dropwise to the well
stirred solution of sodium 2-methyl-3-oxobutyraldehyde (16) (220 g, 1.8 mol)
in acetic acid (650 mL) along with addition of zinc dust in small portions.
During addition of zinc powder (400 g, 6 mol), the reaction temperature was
maintained 85-90 0C. After the addition, the reaction mixture was refluxed
for an additional one hour and then poured into ice/ water (2 L). The crude
product was precipitated as a yellow solid which was colleted by filtration and
wash with water. The solid was dissolved in dichloromethane (800 mL),
filtered again to remove zinc powder and dried over sodium sulfate.
Evaporation of solvent gave the pyrrole which was crystallized from
methanol to give the title compound (104.5 g, 38%): mp. 138-139 0C; 1H NMR
(CDC13) 8 1.98(3H, s, 4-Me), 218 (3H, s, 5-Me), 3.79 (3H, s, OMe), 6.65 (1H, S, 3-
H), 8.95 (1H, br 5, NH); MS for CgHuNOz, found m/ e 153 (M+).

48

Methyl 4,S;dimethyl-3-xtanoylpyrrole-2-carboyylate (18)
Methyl 4,5-dimethylpyrrole-Z-carboxylate (17) (30.6 g, 0.2 mol) was

dissolved in dry dichloromethane (160 mL) with heating. The solution was
cooled to 10 0C in an ice bath and octanoyl chloride (38 mL, 0.22 mol) was
added. To this solution, tin(lV) chloride (35 mL, 0.3 mol) was slowly added
through a pressure-equalized dropping funnel (temperature < 20 0C). After
the addition, the reaction mixture was stirred for another one hour in the ice
bath and then poured into ice/water (200 mL). The organic phase was
separated, washed twice with aqueous sodium carbonate, then with water,
and dried over anhydrous sodium sulfate. The solvent was evaporated
under vacuum to yield a white mass of octanoyl pyrrole (54.2 g, 97%). The
product was essentially pure and no further purification was needed.

For the title compound: mp. 73-75 0C; 1H NMR (CDC13) 5 0.85 (3H, t,
octanoyl Me), 1.27 (8H, m, CH2), 1.63 (2H, q, COCHzglIg), 1.93 (3H, s, 4-Me),
2.17 (3H, s, 5-Me), 2.82 (2H, t, comp, 3.79 (3H, s, OMe), 8.95 (1H, br 5, NH); MS
for C15H7_5N03, found m/ e 279 (M+).

M l 'm th 1- 0 an 1 ole-2- ar la

Methyl 4,5-dimethylpyrrole-Z-carboxylate (17) (30.6 g, 0.2 mol) was
treated with lauroyl chloride (50.9 mL, 0.22 mol), following the method
described for the octanoylpyrrole (4) to give the title compound (65.3 g, 97.6%).
The product was essentially pure and no further purification was needed.

For the title compound: mp. 71-72 0C; 1H NMR (CDC13) 8 0.84 (3H, t,
dodecanoyl Me), 1.30 (16H, m, 012), 1.64 (2H, q, COG—1&2), 1.92 (3H, s, 4—Me),
2.18 (3H, s, 5-Me), 2.82 (2H, t, COC_I;I__2_), 3.80 (3H, s, OMe), 8.95 (1H, br 5, NH); M5
for C20H33N 03, found m/ e 335 (Mt).

49

Memyl 4,5;dimethyl-S-eetylpmole—Z-carboxylate (20)
Sodium borohydride (7.5 g, 0.2 mol) was added to the essentially pure

methyl 4,5-dimethyl-3-octanoylpyrrole-Z-carboxylate (18) (27.9 g 0.1 mol)
dissolved in dry tetrahydrofurane (100 mL). The reaction mixture was cooled
to 10 0C with stirring in an ice bath and boron trifluoride etherate (37 mL 0.3
mol) was slowly added so that the reaction temperature was maintained
below 20 0C. After the addition of boron trifluoride etherate, the mixture was
stirred for an additional one hour in the ice bath and then poured into a
mixture of ice (200 mL), hydrochloric acid (IN, 50 mL) and dichlormethane
(200 mL). The organic phase was separated and washed with hydrochloric
acid (0.5N, 200 mL). Methanol (50 mL) was added and the solvent was
evaporated to dryness. The white product was crystallized from methanol-
water (85:15) to yield the title compound (26.2 g, 98%): mp. 77-80 0C; 1H NMR
(CDCl3) 8 0.85 (3H, t, octyl Me), 1.25-1.45 (12H, m, CH2), 1.90 (3H, s, 4-Me), 2.18
(3H, s, 5-Me), 2.66 (2H, t, 012), 3.79 (3H, s, OMe), 8.55 (1H, br 5, NH); M5 for
C15H27N02, found In / e 265.20, calcd m/ e 265 (M+).

4 ' l- 1 l 2 ar lat

Methyl 4,5-dimethyl-3-dodecanoylpyrrole-Z-carboxylate (19) (33.5 g, 0.1
mol) was treated with sodium borohydride (7.5 g, 0.2 mol) and boron
trifluoride etherate (37 mL, 0.3 mol) following the method described for the
octylpyrrole (5) to give the title compound (31.5 g, 98%), after crystallization
from methanol-water (85:15): mp. 75-78 0C; 1H NMR (CDC13)5 0.86 (3H, t,
octyl Me), 1.25-1.53 (20H, m, CH2), 1.91 (3H, s, 4-Me), 2.18 (3H, s, 5-Me), 2.67
(2H, t, CH2), 3.80 (3H, s, OMe), 8.55 (1H, br 5, NH); M5 for C20H35N02, found
m/ e 321 (M+).

50

 

A mixture of methyl 4,5-dimethyl-3-octylpyrrole-2-carboxylate (20) (5.3
g, 0.02 mol), 48% hydrobromic acid (5 mL) and 88% formic acid (50 mL) was
heated on a steam bath for 80 minutes until effervescense subsided. After

standing overnight, chunky solids formed were collected by filtration, and

recrystallized from methanol / hexane to give the title compound as red-
orange sparkling crystals (4.4 g, 87%): 1H NMR (CDC13) 6 0.85 (6H, t, octyl Me),
1.30 (20H, m, CH2), 1.48 (4H, q, CH2), 1.95 (6H, s, 4,4'-Me), 2.58 (4H, t, CH2), 2.62
(6H, s, 5, 5'-Me), 6.99 (1H, s, methine), 12.90 (2H, br 5, NH); M5 for
C29H49N2Br, found m / e 426 (Mt).

 

Methyl 4,5-dimethyl-3-dodecylpyrrole-2-carboxylate (21) (6.5 g, 0.02 mol)
was treated with 48% hydobromic acid (5 mL) and 88% formic acid (50 mL)
following the procedure described for the 3,3'-dioctyl-2,2'-dipyrrylmethenium
bromide (22) to afford the title compound (10.8 g, 87.5%), after crystallization
from methanol/ hexane: 1H NMR (CDC13) 8 0.86 (6H, t, octyl Me), 1.32 (36H,
m, CH2), 1.46 (4H, q, CH2), 1.96 (6H, s, 4, 4'-Me), 2.58 (4H, t, CH2), 2.62 (6H, s, 5,
5'-Me), 7.00 (1H, s, methine), 12.90 (2H, br 5, NH); M5 for C37H55N2Br, found
m/ e 538 (M+).

l -a x m th 1-4- 2-me hox ar 11 leth l - -me h 1 rr le-2-
magma

Lead tetraacetate (48.7 g, 0.11 mol) was added to a solution of (24) (32.9 g,
0.1 mol) in glacial acetic acid (150 mL) with stirring at room temperature. The
reacton was accomplished by heating on a steam bath for one hour and then

the reaction mixture was poured into a large amount of water ( > 1 L). The

51

precipitated solid was separated by filtration, rinsed with water, and
crystallized from aqueous acetone to give the title compound as ivory-white
needles (34.4 g, 95%): mp. 111-112 0C; 1H NMR (CDC13) 8 2.04 (3H, s, 3-Me),
7.26 (3H, s, CH3CO), 2.43 (2H, t, szCO), 2.76 (2H, t, CHzfigCO), 3.64 (3H,
s, OMe), 5.02 (2H, s, CHgCOzgflg), 5.28 (2H, s, Cal-Isffl20), 7.38 (5H, m, phenyl
H), 9.09 (1H, br 5, NH); M5 for C20H23N05, found m/ e 373 (M+).

'--i 2-me o car-on leth l- ' oiben lo ar-on l-44'---im h l-_ '-
than

Benzyl 5-acetoxymethyl-4-(2-methoxycarbonylethyl)-3-methylpyrrole-2-
carboxylate (25) (280 g, 0.75 mol) was dissolved in 70% acetic acid-water (200
mL) and heated to reflux for one hour. After reaction was accomplished, the
hot reaction mixture was poured into a large amount of water and allowed to
cool down slowly to precipitate solid product. The precipitated solid was
collected by filtration, washed with water, and crystallized from ethanol to
give the title compound as ivory-white needles (188.7 g, 82%): mp. 96-97 0C;
1H NMR (CDC13) 8 2.28 (6H, s, 4, 4'-Me), 2.50 (4H, t, figCHzCO), 2.76 (4H, t,
CH2QI_-I_2CO), 3.58 6H, s, OMe), 3.96 (2H, s, 2, 2'-methane), 5.24 (4H, s,
OCH;_C5H5). 7.33 (10H, m, phenyl protons), 9.29 (2H, br 5, NH); M5 for
C35H33N 203, found 614 (M"').

 

Qipmylmeghenium bromide (28)
3,3'-Bis(2-methoxycarbonylethyl)-5,5'-dibenzyloxycarbonyl-4,4'-
dimethyl-2,2’-dipyrrylmethane (26) (16 g, 0.026 mol) was dissolved in freshly

distilled tetrahydrofuran (300 mL) containing a few drops of triethylamine.
10% Palladium/ carbon (0.5 g) was added and the reaction mixture was
hydrogenated under hydrogen (1 atm, room temperature) until hydrogen
uptake ceased. The solvent was evaporated and dried under vacuum without
removing the catalyst by filtration because the resultant 2,2'-dipyrrylmethane-
5,5'-dicarboxylic acid (27) is only slightly soluble in tetrahydrofuran. The
dried reaction mixture, which contains the compound (27) and catalyst
carbon, was added in a mixture of 98-100% formic acid (85 mL) and bromine
(8.5 mL) in small portions. The reaction was accomplished by stirring at room
temperature for an additional one hour after the addition, and then carbon
was filtered off and washed with formic acid. Most of formic acid was
removed under reduced pressure and then diethyl ether (50 mL) was added to
precipitate the purple solid product. The purple solid was collected by
filtration and rinsed with cyclohexene and hexane to give the title compound
(12.20 g, 80.5%): mp. 180-182 0C; 1H NMR (CDC13) 8 2.05 (6H, s, 4, 4'-Me), 2.59
(4H, t, CH2CH2CO), 3.07 (4H, t, CHzggCO), 3.60 (6H, S, OMe), 7.59 (1H, s,
methine), 14.12 (2H, br 5, NH); M5 for C19H23N2O4Br3, found m/ e 503 (M+).

Dim h12 218-t am hl- 7-i lorh 'n-1317-dir inat
4,4',5,5'-Tetramethyl-3,3'-dioctyl-2,2’-dipyrrylmethenium bromide (22)

(5.05 g, 0.01 mol) and 5,5'-dibromo-3,3'-bis(2-methoxycarbonylethyl)-4,4'-

dimethyl-2,2'-dipyrrylmethenium bromide (28) (5.83 g, 0.01 mol) were

dissolved in anhydrous formic acid (50 mL). To this reaction mixture ,

53

bromine (0.52 mL, 0.01 mol) was added and the mixture was heated to reflux
in an oil bath for 2 hours. The solvent was allowed to boil off over 4 hours
with a stream of air or until completely dried. Methanol (100 mL) and
concentrated sulfuric acid (2 mL) were added to the dried reaction residue,
followed by addition of trimethyl orthoformate (5 mL). After standing
overnight, protected from moisture, the reaction mixture was diluted with
dichloromethane (100 mL) and then neutralized with saturated aqeous
sodium acetate (100 mL). The organic layer was separated, washed once again
with saturated aqueous sodium acetate(60 mL) and then three times with
water (100 mL). After evaporation of the solvent, the residue was
chromatographed on silica gel column (50 to 250 mesh) with 1% methanol in
dichloromethane as eluent. A dark non-fluorescent forerun was discarded
and the moving porphyrin band on chromatography column can be
monitored by using UV-lamp to ensure a complete collection. The fractions
containing porphyrin were combined, evaporated to dryness under vacuum,
and crystallized from dichloromethane and methanol to give the title
compound as sparkling crystals (0.46 g, 6%): 1H NMR (CDC13) 8 -3.80 (2H, br 5,
NH), 0.82 (6H, t, octyl Me), 1.28 (12H, m, CH2) 1.49, 1.72, 2.27 (4H each, q, CHz),
3.28 (4H, t, CHflgCO), 3.60, 3.63, 3.64 (6H each, s, 2, 8, 12, 18-Me and OMe),
4.03 (4H, t, CH2), 4.41 (4H, t, CH2CH2C02), 10.07, 10.08 (1H each, s, Meso H),
10.09 (2H, s, meso H); UV-vis (in CH2C12) Am (8“) 620 nm (5,100), 566 (7,000),
531 (10,200), 498 (14,300), 398 (178,100); M5 for C43H66N4O4, found m/ e 763
(M+).

54

Dimethyl 2,§,12,18-tetramethyl-3,7-didede_c_ylp_orphyrin-13,17-gipropienate
£3.02

4,4',5,5'-Tetramethyl-3,3'-didodectyl-2,2'-dipyrrylmethenium bromide
(23) (6.17 g, 0.01 mol) and 5,5'-dibromo-3,3'-bis(2-methoxycarbonylethyl)-4,4'-
dimethyl-2,2'-dipyrrylmethenium bromide (28) (5.83 g, 0.01 mol) was treated
with one equivalent of bromine in anhydrous formic acid (50 mL) as
described before for the dioctylporphyrin (29) to give the title compound (0.49
g, 5.6%), after crystallization from dichloromethane and methanol: 1H NMR
(CDCl3) 8 -3.90 (2H, br 5, NH), 0.84 (6H, t, dodecyl Me), 1.21 (32H, m, CH2), 1.49,
1.71, 2.27 (4H each, q, CH2), 3.29 (4H, t, CI-IflgCO), 3.57, 3.60, 3.69 (6H each, 3,
ring Me, OMe), 3.99 (4H, t, CH2), 4.39 (4H, t, Qfl_2_CH2CO), 9.97, 9.99, 9.99, 10.00
(1H each, s, meso H); UV-vis (in CH2C12) Amax (EM) 620 nm (5,200), 566 (7,100),
531 (10,100), 497 (14,400), 398 (177,900); M5 for C55H82N4O4, found m/ e 875
(Mt).

Dimeh 1281218-tetram h 1-2 7- i l- h 'n ne-l 17- ' ro i na

(35), Dimethyl 2,8,12,18-tetramethyl-S,7-dieggyl-13-porphyrinene-12,17-
QI'prepionate (32) I
Osmium tetroxide (310 mg, 1.2 mmol) and pyridine (1 mL) were added
to dimethyl 2,8,12,18-tetramethyl-3,7-dioctylporphyrin-l3,17-dipropionate (29)
(763 mg, 1.0 mmol) dissolved in dichloromethane (100 mL). After the
reaction mixture was stirred for 24 hours at room temperature under
nitrogen in the dark for 24 hours, it was quenched by adding methanol (50
mL), then bubbled with hydrogen sulfide through the reaction solution for 20
minutes to decompose the osmate adducts and allowed to stand for 1-2 hours.
The precipitated black osmium sulfide was removed by filtration through a

bed of Celite. Evaporation of the filtrate gave crude intermediates (vic-

55

dihydroxychlorins (31) and (33)) which were subsequently treated with
concentrated sulfuric acid (10 ml) for 30 minutes at room temperature
without further purification. The reaction mixture was cooled in an ice bath
and diluted with methanol (50 mL). The reaction solution was then allowed
to stand overnight at room temperature, protected from moisture, to ensure
re-esterification. The solution was diluted with dichloromethane (100 mL)
and the organic layer was washed twice with saturated aqueous sodium
acetate (100 mL) and twice with water (100 mL). The organic layer was dried
over anhydrous sodium sulfate and the solvent was removed under vacuum
and the residue was chromatographed on silica gel with 1% methanol in
dichloromethane as eluent. The porphyrinone (35) (250 mg, 46% yield based
on reacted (29))was isolated as the major product along with the unreacted
porphyrin (29) (230 mg). A small amount of the isomeric porphyrinone (37)
(10 mg, 1.3%) was also obtained.

For dimethyl 2,8,12,18-tetramethyl-2,7-dioctyl-3-porphyrinone-13,17-‘-
dipropionate (35): 1H NMR (CDCl3) 8 -3.05 (2H, br 5, NH), 0.65 (3H each, t,
octyl Me), 0.90 (12H, m, CH2), 1.30 (6H, m, CH2), 1.45, 1.69, 2.19 (2H each,q,
CH2), 2.04 (3H, s, 2-Me), 2.70 (2H, t, 7—CH2), 3.19, 3.26 (2H each, t, ClimCOz),
3.48, 3.57, 3.57, 3.65, 3.66 (3H each, s, 8, 12, 18-Me, OMe), 3.90 (2H, dt, 2-CH2),
4.24 (2H, t, lflCHzCOz), 4.40 (2H, t, 17-QI_I_2CH2C02), 9.14, 9.82, 9.89, 9.93
(1H each, s, meso H); UV-vis (in CH2C12) Am (8“) 641 nm (36,500), 614 (2,000),
586 (5,700), 547 (13,200), 508 (9,300), 405 (162,300); M5 for C48H66N405, found
m/ e 779 (Mi').

For dimethyl 2,8,12,18-tetramethyl-3,7-dioctyl-13-porphyrinone-12,17-
dipropionate (37): 1H NMR (CDC13) 8 -2.95 (2H, br 3, NH), 0.65 (3H each, t,
octyl Me), 0.90 (12H, m, CH2), 1.30 (6H, m, CHz), 1.47, 1.70, 2.20 (2H each, q,
CH2), 2.05 (3H, s, 12-Me), 2.72 (2H, t, 3—CH2), 3.25 (4H, dt, CH&H2_C02), 3.58,

56

3.58, 3.66, 3.67, 3.73 (3H, each, s, 2, 8, 18-Me, OMe), 3.98 (2H, dt, IZ-Q-IZCHzCOz),
4.34 (2H, t, 7-CHz), 4.40 (2H, t, 17—QI-_I;CHzCOz), 9.13, 9.80, 9.95, 10.13 (1H each, s,
mesa H); UV-vis (in CH2C12) Am (EM) 639 nm (37,000), 583 (2,300), 551 (6,400),
511 (12,800), 408 (9,700); M5 for C43H66N405, found m/ e 779 (M+).

Dimethyl 2,§,1 2 ,1 8-tetramethyl-2,7-gidodecyl-3-porphyrinene-1S ,1 7-

i r i na . Dimeth l 2 12 1 - etrameth l- 7- i e l-1 -
mmhym eng12,17;g1iprepionate (38)

Dimethyl 2,8,12,18-tetramethyl-3,7-didodecylporphyrin-13,17-
dipropionate (30) (875 mg, 1.0 mmol) was treated with some excess of osmium
tetroxide and then with concentrated sulfuric acid by following the methode
described before for the dioctylporphyrinones (35) and (37) to afford the
didodecylporphyrinone (36) (249 mg, 43% yield based on reacted (30)) as the
major product along with the unreacted porphyrin (30) (307 mg). A small
amount of the isomeric porphyrinone (38) (17 mg, 1.9%) was also obtained.

For dimethyl 2,8,12,18-tetramethyl-2,7-didodecyl-3-porphyrinone-13,17-
dipropionate (36): 1H NMR (CDC13) 8 -2.95 (2H, 5, NH), 0.80, 0.85 (3H each, s,
dodecyl Me), 0.98-1.35 (34H, m, CHz), 1.45, 1.70 (2H each, q, CH2), 2.05 (3H, s, 2-
Me), 2.20 (2H, q, CH2), 2.70 (2H, t, 7-CH2), 3.20, 3.27 (2H each, t, CHfilngOfi,
3.47, 3.57, 3.58, 3.67, 3.68 (3H each, s, 8, 12, 18,-Me, OMe), 4.00 (2H, dt, 2-CH2),
4.24, 4.40 (2H each, t, SligCHzCOz), 9.14, 9.82, 9.89, 9.93 (1H each, s, meso H);
UV-vis (in CH2C12) Am (8,.) 641 (36,000), 586 (5,500), 546 (13,100), 509 (9,500),
405 (162,000); M5 for C56H32N405 found m/ e 891.3 (Mi).

For dimethyl 2,8,12,18-tetramethyl-3,7-didodecyl-13-porphyrinone-
12,17-dipropionate (38): 1H NMR (CDC13) 8 -2.90 (2H, 5, NH), 0.80, 0.90 (3H, t,
Octyl Me), 1.00-1.20 (34H, m, CH2), 1.50, 1.70 (2H each, q, CH2), 2.10 (3H, s, 12-
Me), 2.70 (2H, t, 3-CI-12), 3.20 (4H, t, (3293502), 3.58, 3.57, 3.65, 3.65, 3.72 (3H

57

each, s, 2, 8, 18, -M, OMe), 4.02 (2H, dt, 12-CLI2CH2C02), 4.30 (2H, t, 7-CH2), 4.40
(2H, t, 17-QI-QCH2C02), 9.12, 9.80, 9.95, 10.14 (1H each, s, meso H); UV-vis (in
CH2C12) lmax (EM) 639 nm (37,500), 583 (2,400), 551 (6,500), 511 (12,800), 409
(9,900); M5 for C56H32N4Os, found m/ e 891 (Mt).

 

dimionateml
Osmium tetroxide (207 mg, 0.8 mmol) and pyridine (0.5 mL) were
added to (35) (390 mg, 0.5 mmol) dissolved in dry dichloromethane (50 mL).

The reaction was allowed to proceed at room temperature in the dark for 24
hours and worked up in the same manner as described before. After osmium
tetroxide oxidation, sulfuric acid catalyzed rearrangement was accomplished
as described previously. The porphyrindione (43), was isolated as the major
product (95 mg, 30% yield based on reacted (35) along with the unreacted
porphyrinone (35) (74 mg), the former moved slower on the silica gel column
than the latter.

For the title compound: 1H NMR (CDC13)8 -2.81, -2.76 (1H each, 5,
NH), 0.64, 0.84 (3H each, t, octyl Me), 0.90 (14H, m, CH2), 1.27 (6H, m, CH2),
1.46, 1.66 (2H each, dq, CH2), 1.97, 2.02 (3H each, s, 2, 12-Me), 2.16 (2H, dt, 12-
CH2Q12C02), 2.65 (2H, t, 17-CHLCL12CO2), 3.01 (2H, dt, 2-CH2), 3.20 (2H, t, 7-
CH2), 3.32, 3.47, 3.51, 3.75 (3H each, s, 8, 18-Me, OMe), 3.92, 4.29 (2H each, t,
CflgCHzCOz), 9.04, 9.05, 9.66, 9.68 (1H each, s, meso H); UV-vis (in CH2C12)
Amax (SM) 685 nm (101,800), 651 (7,000), 621 (5,300), 552 (9,000), 511 (6,000), 485
(3,700), 409 (182,300); M5 for C431-I66N405, found m/ e 795 (M+).

Dimethyl 2.8.12.18-tetramethyl-2,7-didodecyl-3,1S-porphyrinedione-IZJ7-
i r i nate

Dimethyl 2,8,12,18-tetramethyl-2,7-didodecyl-3—porphyrinone-13,17-
dipropionate (36) (446 mg, 0.5 mmol) was treated with some excess of osmium
tetroxide and then with concentrated sulfuric acid following the procedure
described before for the dioctylporphyrindione (43) to give the
didodecylporphyrindione (44) (99.8 mg, 27% yield based on reacted (36)) as the
major product along with the unreacted porphyrin (36) (83 mg).

For the title compoundle NMR (CDCL3) 8 -2.80, -2.74 (1H each, 5,
NH), 0.64, 0.84 (3H each, t, dodecyl Me), 1.00 (30H, m, CHz), 1.30 (6H, m, CH2),
1.46, 1.68 (2H each, q, CH2), 1.95, 2.00 (3H each, s, 2, 12-Me), 2.14 (2H, dt, 12-
CHLQ-IgCO2), 2.65 (2H, t, 17-CH2_(;I_-I_2_C02), 3.00 (2H, dt, 2-CH2), 3.22 (2H, t, 7-
CH2), 3.30, 3.46, 3.52, 3.75 (3H each, s, 8, 18-Me, OMe), 3.92 (2H, dt, 12-
93120-1sz, 4.28 (2H, t, 17-fi2_CH2C02), 9.05, 9.06, 9.66, 9.69 (1H each, s, meso
H); UV-vis (in CH2C12) Amax (EM) 685 nm (101,000), 651 (6,900), 621 (5,100), 552
(9,000), 511 (5,900), 486 (3,700), 409 (182,100); MS for C56H32N405, found m/ e
907 (Mt).

 

W145)
Dimethyl 2,8,12,18-tetramethyl-2,7-dioctyl-3-porphyrinone-13,17-

dipropionate (35) (93.4 g, 0.12 mmol) was dissolved in 100 mL of the mixture
of chloroform-methanol (3:1) and a solution of copper(II) acetate
monohydrate (72 mg, 0.36 mmol) in methanol (7 mL) was added. The
reaction mixture was refluxed for 30 minutes and then cooled to room
temperature. Excess copper(II) acetate and methanol were removed by

washing with a large amount of water. Copper(II) porphyrinone derivative

59

(35), resulted from evaporation of solvent, was dissolved in dry chloroform
(50 mL) and treated with titanium(IV) chloride (0.2 mL, 0.18 mmol) and with
a solution of malonitrile (31.7 mg, 0.48 mmol) and pyridine (0.08 mL, 1
mmol) in dry chloroform (10 mL), which was prepared one hour before use.
After the reaction was accomplished by refluxing for 30 minutes, the reaction
mixture was cooled to room temperature, diluted with chloroform (50 mL),
washed with water (2xlOO mL), and dried over anhydrous sodium sulfate.
The solvent was removed under vacuum. The resulting residue, copper(II)
complex of dicyanomethylenylchlorin, was dissolved in trifluoroacetic acid
(15 mL), bubbled with hydrogen sulfide through the reaction solution for 20
minutes to remove copper from the dicyanomethylenylchlorin, and allowed
to stand for 1-2 hours. The precipitated black copper(II) sulfide was removed
by filtration through a bed of Celite which was rinsed with chloroform (20
ml), the filtrates were combined and washed twice with saturated aqueous
sodium acetate (20 mL) and twice with water (20 mL). The solvent was
removed under vacuum and the residue was chromatographed on silica gel
with 0.5-1% methanol in dichloromethane to give the title compound(46.6
mg, 47%): 1H NMR (CDC13) 8 -2.63, -2.47 (1H each, br 5, NH), 0.65, 0.85 (3H
each, t, octyl Me), 0.90-1.04 (12H, m, CI-Iz), 1.26 (6H, m, CH2), 1.44, 1.69, 2.20 (2H
each, q, CHz), 2.35 (3H, s, 2-Me), 2.89 (2H, t, 7-CH2), 3.16, 3.24 (2H each, t,
CHfiflgCoz), 3.39, 3.49, 3.53, 3.66, 3.68 (3H each, s, 8, 12, 18-Me, OMe), 3.95 (2H,
dt, 2421-12), 4.14, 4.32 (2H each, t, g‘,I_-12CH2C02), 9.97, 9.68, 9.75, 10.70 (1H each, s,
meso H); UV-vis (in CH2C12) Amax (8”) 678 nm (32,000), 627 (23,000), 459
(70,000), 405 (41,000), 381 (40,400), 345 (27.800); MS for C51H66N604, found m/ e
827 (M+).

60

Dimethyl S-dicyanomethylenyl-Z,8,12,18-tetramethyl-2,7-didodecylchlorin-

13,17fliprepienate (46)
Dimethyl 2,8,12,18-tetramethyl-Z,7-didodecyl-3-porphyrinone-13,17-

dipropionate (36) (89.2 mg, 0.1 mmol) was treated with copper(II) acetate and
then with a solution of malonitrile (26 mg, 0.4 mmol) and pyridine (0.07 mL,
0.87 mmol) in dry chloroform (9 mL) in the presence of titanium(IV) chloride
(0.19 mL, 0.15 mmol) following the method described before for the
dicyanomethylenyl dioctylchlorin (45) to afford the title compound (46) (43.2
mg, 46%): 1H NMR (CDC13) 8 -2.62, -2.47 (1H each br S, NH), 0.65, 0.86 (3H
each, t, dodecyl Me), 0.92-1.08 (20H, m, CH2), 1.26 (14H, m, CH2), 1.45, 1.70, 2.19
(2H each, q, CHz), 2.36 (3H, s, 2-Me), 2.90 (2H, t, 7-CI-12), 3.16, 3.25 (2H each, t,
CHZCAI2CO2), 3.40, 3.49, 3.54, 3.66, 3.68 (3H each, 5, ring Me, OMe), 3.96 (2H, dt,
2-CH2), 4.14, 4.32 (2H each, t, CH2CH2C02), 9.97, 9.69, 9.76, 10.71 (1H each, s,
meso H); UV-vis (in CH2C12) Amax (8M) 678 nm (31,500), 627 (22,700), 459
(69,000) 405 (40,800), 381 (40,200), 345 (27,400); M5 for C59H32N5O4, found 939
(M1).

Bi 'meth lSil l -carbodiimide

To a solution of chlorotrimethylsilane (25.7 mL, 0.2 mol) and
triethylamine (27.9 mL, 0.2 mol) in dry diethyl ether (50 mL), a solution of
cyanamide (4.2 g, 0.1 mol) in dry diethyl ether (50 mL) was added with stirring
within one hour. The triethylamine hydrochloride, byproduct, was removed
by filtration and the filtrate was distilled under reduced pressure to give the
title compound as colorless liquid (32 g, 86%): hp 67-72 0C / water aspirator;
1H NMR (CDC13) 8 1.21 (18H, 5, Me); M5 for C7H13N25i2, found 186.4 (M't).

 

To a solution of dimethyl 2,8,12,18-tetramethyl-2,7-dioctyl-3-

porphyrinone-13,17—dipropionate (35) (31 mg, 0.04 mmol) in dichloromethane
(30 mL), titanium(IV) chloride (0.013 mL, 0.12 mmol) and bis(trimethylsilyl)-
carbodiimide (0.03 mL, 0.12 mmol) was consecutively added under argon.
The reaction mixture was allowed to stir at room temperature for 4 hours.
After the reaction was accomplished which was monitored by TLC, the
reaction mixture was filtered through a bed of Celite and the filtrate was
washed twice with water (30 mL) and dried over anhydrous sodium sulfate.
The solvent was evaporated under vacuum and the residue was
chromatographed on silica gel with 0.5% methanol in dichloromethane to
give the title compound as major procduct (18.9 mg, 59% ): 1H NMR (CDC13)
8 -2.78, -2.71 (1H each, br 5, NH), 0.66, 0.88 (3H each, t, octyl Me), 0.99-1.05 (12H,
m, CHz), 1.30 (6H, m, CH2), 1.50, 1.69, 2.20 (2H each, q, CH2), 2.40 (3H, s, 2-Me),
2.98 (2H, dt, 7-CHfl, 3.19, 3.28 (2H each, t, CI-IfiflgCOz), 3.40, 3.48, 3.57, 3.67, 3.69
(3H each, s, 8, 12, 18-Me, OMe), 3.92 (2H,dt, 2-CH2), 4.18, 4.47 (2H each, t,
§I_-I_2_CH2C02), 9.06, 9.78, 10.00, 10.94 (1H each, s, meso H); UV-vis (in CH2C12)
Am (8“) 660 nm (16,500), 599 (10,700), 439 (64,500), 384 (29,200), 337 (14,000);
M5 for C49H65N604, found m/ e 803 (Mt).

 

giprepienate (43)
Dimethyl 2,8,12,18-tetramethyl-Z,7-didodecyl-3-porphyrinone-13,17-

dipropionate (36) (35.7 mg, 0.04 mmol) was treated with an excess of
bis(trimethylsilyl)-carbodiimide in the presence of titanium(IV) chloride
(0.013 mL, 0.12 mmol) following the method described before for the dimethyl

62

N -cyanoiminyl dioctylchlorin (47) to give the title compound as major
product (22.5 mg, 60%): 1H NMR (CDC13) 8 -277, -2.71 (1H each, br 5, NH)
0.67, 0.89 (3H each, t, dodecyl Me), 0.96-1.12 (20H, m, CH2), 1.31 (14H, m, CH2),
1.50, 1.70, 2.21 (2H each, q, CH2). 2.40 (3H, s, 2-Me), 2.99 (2H, dt, 7-CH2), 3.19,
3.29 (2H each, t, CHmCOfi, 3,40, 3.48, 3.58, 3.67, 3.70 (3H each, s, 8.12, 18-Me,
OMe), 3.93 (2H, dt, 2-CI-12), 4.18, 4.47 (2H each, t, SligCI-I2C02), 9.06, 9.78, 10,00,
10.94 (1H each, s, meso H); UV-vis (in CH2C12) Amp, (8“) 660 nm (16,500), 599
(10,700), 439 (64,500), 384 (29,200), 337 (14,000); M5 for C57H32N504, found m/ e
915 (M+).

 

diprepionate (42)

Lawesson's reagent (48 mg, 0.12 mmol) was added to a solution of

dimethyl 2,8,12,18-tetramethyl-2,7-dioctyl-3-porphyrinone-13,17-dipropionate
(35) (77.8 mg, 0.1 mmol) in dry toluene (50 mL) under nitrogen. After the
reaction mixture was refluxed for 24 hours under nitrogen, the solvent was
removed under high vacuum. The resulting residue was chromatographed
on Silica gel with 30% haxane in dichloromethane to isolate the
porphyrinthione as the major product which was further purified by
recrystallization from dichloromethane and methanol to give the title
compound (34.7 mg, 44%): 1H NMR (CDC13) 8 -2.50 (2H, br 5, NH), 0.66, 0.88
(3H each, t, octyl Me), 0.90-1.05 (12H, m, CH2), 1.60 (6H, m, CHz), 1.50, 1.68, 2.20
(2H each, q, CHz), 2.08 (3H, s, 2-Me), 2.75, 2.95 (1H each, dt, 7-CH2), 3.19, 3.27
(2H each, t, CHfiigCOz), 3.40, 3.48, 3.56, 3.67, 3.69 (3H each, s, 8, 12, 18-Me,
OMe), 3.95 (2H, dt, 2-CH2), 4.18, 4.36 (2H each, t, §I_-I_2CH2CO2), 9.13, 9.74, 9.74,
10.32 (1H each, s, meso H); UV-vis (in CI-12C12) lmax (SM) 679 nm (26,000), 623

63

(22,000), 457 (75,000), 441 (69, 600) 405 (59,200), 384 (52,600), 345 (33,700), 313
(21,000); MS for C43H66N4O4S, found 795 (Mt).

Dimethyl 2,S,12,18-getramethyl-2,7-g1idodecyl-S-porphyrinthione-IS.17-
' r ' na e

Dimethyl 2,8,12,18—tetramethyl-Z,7-didodecyl-3-porphyrinone-13,17-
dipropionate (36) (89.2 mg, 0.1 mmol) was treated with an excess of
Lawesson's reagent following the method described for the dioctyl
porphyrinthione (49) to give the title compound as a major product (39 mg,
43%): 1H NMR (CDCl3) 8 -2.52, -2.49 (1H each, br 5, NH), 0.77, 0.84 (3H each, t,
dodecyl Me), 0.90-1.12 (20H, m, CH2), 1.23 (14H, m, CH2), 1.49, 1.67, 2.20 (2H
each, q, CH2), 2.08 (3H, s, 2-Me), 2.72, 2.92 (1H each, dt, 7-CH2), 3.18, 3.25 (2H
each, t, CHygl-ngOfl. 3.42, 3.52, 3.54, 3.66, 3.67 (3H each, s, 8, 12, 18-Me, OMe),
3.97 (2H, dt, 2-CH2), 4.19, 4.35 (2H each, t, ijgCHzCOZ), 9.12, 9.73, 9.77, 10.30
(1H each, s, meso H); UV-vis (in CH2C12) lmax (SM) 679 nm (25,700), 623
(21,900), 457 (74,800), 441 (69,400), 405 (59,000), 384 (52,400), 345 (33,500), 313
(20,800); M5 for C56H32N4O4S, found m/ e 907 (Mt).

Dimethyl SJS-bistN-gyaneiminyl)-2,§,12.1S-tegramethyl-2J-
‘ l a ri rin-l 7 i r i na

Dimethyl 2,8,12,18-tetramethyl-2,7-dioctyl-3,13-porphyrindione-12,17-
dipropionate (43) (39.7 mg, 0.05 mmol) was dissolved in dry dichloromethane
(30 mL) and bis(trimethylsilyl)-carbodiimide (0.04 mL, 0.15 mmol) was added
followed by addition of titanium(IV) chloride (0.03 mL, 0.15 mmol) under
nitrogen. After the reaction was completed by stirring at room temperature in
the dark for 4 hours, which was monitored by TLC eluted with hexane-

dichloromethane (1:3), the reaction mixture was filtered through a bed of

Celite and the filtrate was washed twice with water (40 mL). The organic layer
was separated and dried over anhydrous sodium sulfate. Evaporation of the
solvent gave a residue which was purified by preparative thick layer plates
(silica gel) eluted with hexane-dichloromethane (1:3). The product was
extracted from the silica gel to afford the title compound (17.7 mg, 42%): 1H
NMR (CDC13) 8 -2.41 (2H, br 5, NH), 0.62, 0.83 (3H each, t, octyl Me), 0.80-1.02
(12H, m, CI-Iz), 1.30 (6H, m, CH2), 1.43, 1.55, 1.64 (3H each, m, CHz), 2.16, 2.63
(2H, t, CH2CI-I_2C02), 2.28, 2.32 (3H each, s, 212-Me), 2.85 (2H, dt, 2-CH2), 3.20
(2H, t, 7-CH2), 3.46, 3.66, 3.68, 3.71 (3H each, 3, ring Me, OMe), 3.87, 4.23 (2H
each, t, CH2CH2C02), 8,92, 9.77 (2H each, s, meso H); UV-vis (in CH2C12) Amax
(8“) 719 nm (74,000), 654 (9,500), 619 (12,200), 448 (109,800), 426 (95,600); MS for
C50H56N304, found m/ e 843 (M+).

p2. - 1 .i -g. i ‘ 1- .1 1.- -.. -11a-27--ou--Iloq-'.
Dimethyl 2,8,12,18-tetramethyl-2,7-didodecyl-3,13-porphyrindione-
12,17-dipropionate (44) (54.5 mg, 0.06 mmol) was treated with an excess of
bis(trimethylsilyl)-carbodiimide in the presence of titanium(IV) chloride
(0.036 mL, 0.18 mmol) following the method described for the bis(N-
cyanoiminyl)-dioctylbacteriochlorin (51) to give the title compound as a
major product (22.8 mg, 39.8%): 1H NMR (CDC13) 8 -2.42 (2H, br s, NH), 0.63,
0.83 (3H each, t, dodecyl Me), 0.80-1.07 (20H, m, CH2), 1.30 (14H, m, CHz), 1.44,
1.55, 1.65 (3H each, m, CH2), 2.17, 2.65 (2H, t, CH2C_H;_CO2), 2.28, 234 (3H each,
5, ring Me), 2.86 (2H, dt, 2-CH2), 3.21 (2H, t, 7-CH2), 3.45, 3.66, 3.68, 3.72 (3H
each, 5, ring Me, OMe), 3.88, 4.24 (2H each, t, figCHzCOfl, 8,92, 9,78 (2H each,
s, meso H); UV-vis (in CH2C12) Amax (SM) 719 nm (74,000), 654 (9,500), 619
(12,200), 448 (109,800), 426 (95,600); M5 for C53H32N304, found 955 (M+).

65

 

Lawesson's reagent (80 mg, 0.2 mmol) was added to a solution of

dimethyl 2,8,12,18-tetramethyl-2,7-dioctyl-3,13-porphyrindione-12,17-
dipropionate (43) (55.6 mg, 0.07 mmol) in dry toluene (55 mL). After the
reaction mixture was refluxed under nitrogen in the dark for 24 hours, the
reaction was completed which was monitored by TLC using hexane-
dichloromethane (1:3). The solvent was removed under vacuum, and the
residue was purified by preparative thick layer plates (silica gel) eluted with
30% hexane in dichloromethane. The product was extracted from the silica
gel and then crystallized from dichloromethane and methanol to afford the
title compound as green fluffy crystals (20.2 mg, 35%): 1H NMR (CDC13) 8
-1.78, -1.74 (1H each, br s, NH), 0.66, 0.86 (3H each, t, octyl .Me), 0.80-1.08 (12H,
m, CH2), 1.30 (8H, m, CH2), 1.49, 1.66 (2H each, m, CH2), 1.96, 2.02 (3H each, s,
212-Me), 216, 266 (2H each, t, CH2_CI_-_I_2_CO2), 283, 2.98 (1H each, t, 2-CH2), 3.21
(2H, t, 7-CH2), 3.27, 3.40, 3.44, 3.72 (3H each, 5, ring Me, OMe), 3.86, 4.24 (2H
each, t, CHeCH2C02), 8.89, 8.90, 9.97, 10.00 (1H each, S, meso H); UV-vis (in
CH2C12) Amx (SM) 747 nm (92,200), 714 (12,800), 682 (21,900), 655 (17,600), 477
(102,700), 446 (64,500), 431 (79,800); M5 for C43H66N4O452, found 827 (M+).

 

g'prepionate (54)
Dimethyl 2,8,12,18-tetramethyl-2,7-didodecyl-3,13-porphyrindione-

12,17-dipropionate (44) (63.5 mg, 0.07 mmol) was treated with an excess of
Lawesson's reagent following the method described for the dioctyl-

porphyrindithione (53) to give the title compound as a major product (23.6

66

mg, 36%): 1H NMR (CDC13) 8 -1.77, -1.74 (1H each, br 5, NH), 0.67, 0.87 (3H
each, t, dodecyl Me), 0.80-1.12 (20H, m, CH2), 1.30 (16H, m, CH2), 1.50, 1.68 (2H
each, m, CH2), 1.97, 2.04 (3H each, s, 2.12-Me), 2.16, 2.67 (2H each, t,
CH2§I_-12CO2), 3.84, 298 (1H each, t, 2-CH2), 3.22 (2H, t, 7012). 3.27, 3.40, 3.43,
3.72 (3H each, 5, ring Me, OMe), 3.86, 4.25 (2H each, t, C_I;I;CH2CO2), 8.89, 8.90,
9.97, 10.01 (1H each, s, meso H); UV-vis (in CH2C12) Amax (EM) 747 nm (92,200),
714 (12,800), 682 (21,900), 655 (17,600), 477 (102,700), 446 (64,500) 431 (79,800); M5
for C56H32N4O452, found 939 (M+).

CHAPTER 3
SYNTHESES AND PROPERTIES OF
AN IONIC DI-PORPHYRIN DERIVATIVES

I. INTRODUCTION

Photofrin-II suffers from the lack of a defined structure because of its
complex chemical nature. Dougherty et al.103 first described the compound as
dihematoporphyrin ether (55, DHE, and isomers), but it is now generally
accepted to be a mixture of dimers and higher oligomers linked by ether, ester,
and even carbon-carbon bonds.109 Interconversion between ester and ether
links has also been noted.110 Recently, using purer materials, attempts have
been made to understand some of the parameters important for an effective
in viva photosensitizer. An HP dimer joined by ester linkages was
synthesized by Pandey and Dougherty,111 but it was biologically inactive; an
ether linked HP oligomers was synthesized by Scourides et al.,112 but though
it was shown to be as active as Photofrin II, it was also shown to be a complex
mixture.

In 1988, synthesis of a simple ether dimer was first reported by Pandey
and Dougherty.113 It was shown to be an effective in viva sensitizer. Morris
and Ward114 used similar chemistry to obtain DHE tetramethyl ester. Mild
hydrolysis gave DHE (55) but it was inactive. The DHE variants possessing

67

68

one (56) or two vinyls (57) were also synthesized, and the latter was just as

active as Photofrin II.

at CH3 32
CH3 H
CH3 . CH3
H CH3
CH3 0 CH3 CH3 0 CH3
M0020 M9020 002m COZMO

(55) R1=R2= CH(OH)CH3

(56) R1=CH(OH)CH3; R2=CH=CH2
(57) R1=R2= CH=CH2

( all as mixtures of regioisomers)

Recently, Pandey et al.115 have prepared the carbon-carbon linked
dimers related to HP. Treatment of hydroxyethylporphyrin (58) and (59) with
trifluoromethanesulfonic acid (triflic acid) affords > 90% yield of the
corresponding carbon-carbon dimer (60) and (61) respectively as shown in
Semi; In preliminary biological testing for tumorcidal activity, the
tetracarboxylic acid dimer from the dimeric porphyrin (61) was found to be
more active than that from the dimeric porphyrin (60).

69

CHatH0)HC CH. CHaozc CH3
Triflic acid

 

CH3 0 CH3

CO CO CH3
20.4358 2

 

 

H CH3
CH3 CH(OH)CH3 CH3
Triflic acid A
CH3 CH3 CH3
002011: 002Gb
59

 

Schema

A series of dimeric porphyrins linked by 3-, 5-, 6-, and 13-carbon chains
have been prepared in our laboratory. These compounds have been tested in
viva for effectiveness in PDT. The dimers linked with 6-carbon chain proved
to be the most effective against mouse tumor system in viva. The
compounds linked by 3-carbon chain showed no activity in vivo.115v117 The
dimers linked with 5- and 6-carbon chain were at least as efficient as Photofrin
II, and all showed less skin persistence than Photofrin-II. Furthermore,
dimeric tetrahydroxychlorin (63), and dimeric porphyrinone (65) were more
potent than Photofrin II in viva.117 Unfortunately, the methylene-linked

dichlorin derivatives suffered from a lack of regio-specific structure; for

7O

example, it was very difficult to make dimeric porphyrin (64) containing one
oxo group with the oxo position attached at the specific pyrrole.

To control the regio-selectivity and to prepare effective PDT
photosensitizers, we designed a dimeric porphyrin linked by 6-carbon chains
(83, in Scheme 12) which contains both lipophilic character at the "northern"
part and hydrophilic character at the "southern" part in the molecule, which
are called amphiphilic character, to improve intracellular localization.

Although dimeric porphyrins linked by space chains proved to have
higher affinity for tumor tissue than mono-porphyrins, porphyrin dimers
absorb in the same region as mono-porphyrins. Thus, some structural
modifications of porphyrin dimers are needed to increase extinction
coefficients of absorption bands at the longer wavelengths by adding desirable
functional group which are good auxochromes (bathochromic shift).

To prepare dimeric chlorin derivative (85) and dimeric benzochlorin
derivative (86), the porphyrin dimer (83) was first converted to the vinyl
analogue (84) as shown in Scheme 1;. Chlorins typically abosrb strongly in
the red region of the visible light spectrum.118 These compounds have large
extinction coefficients at wavelengths above 650 nm, suggesting improved
light transmission through tissue as well as greater photon efficiency when
compared to porphyrins. The dimeric chlorin derivative (85) was easily

obtained from the reaction of the dimeric vinylporphyrin (84) with singlet
oxygen (102).

71

COOH COOH COOH COOH
62
HOOC COOH
Cs
0
OH
COOH COOH coon COOH
63
HOOC COOH
Cs
HOOC 0
COOH coon COOH
64
Ce
HOOC O . 0 COOH
COOH coon

72

Benzochlorin derivatives have significant extinction coefficients at
around 680 nm and appear to have low density lipoprotein (LDL) mediated
localization parameters similar to those observed with I-IPD.119

“Ceozc COzMe

002m M9020 002m M0020

Schema

A number of years ago, Johnson and co-workers120 reported a facile
synthesis of compounds possessing the chlorin chromophore by using the
Diels-Alder reaction on vinylporphyrins. Dolphin et (21.121 extended this
methodology and showed that the reaction of the vinyl groups of
protoporphyrin D< dimethyl ester (66) with dimethyl acetylenedicarboxylate
(DMAD) gave initially the Diels-Alder adducts (67) and (68), as shown in
Sc_l_;eme 7, which could be rearranged by treatment with base. The reaction
with triethylamine (TEA) or 1,5-diazabicyclol5.4.0]undec-5-ene (DBU) gave, in
every case, two diastereomers, where the former rearrangement led to the
kinetically controlled product and the latter the thermodynamically
controlled one as shown in W. Recently Smith et al.122 eliminated the

problem of isomer formation in the Diels-Alder reaction of protoporphyrin

73

D( dimethyl ester (66) due to its asymmetry by using symmetrically substituted
divinylporphyrins.

TEA MeO DBU

 

 

   

67 or 68
Schemefi

We achieved significant simplification in the regioselectivity of the
Diels-Alder reaction of the symmetrically substituted dimeric vinylporphyrin
(84) with electron-deficient DMAD as follows (see Scheme 9). Diels-Alder
reaction of the dimeric vinylporphyrin (84) with DMAD gave initially the
Diels-Alder adduct (69) which was rearranged by DBU to give the
thermodynamically controlled isomer (86) as mentioned before.

H H O H
\ DMAD A M00 H DBU MOO H
v M00 7 M90 .
// l I l T I l
N 0M0 N 0M9 N
86

 

 

“he. \ fit...

84 69
Sshemea

74

II. SYNTHESES

As shown in Scheme 12, to obtain the dimeric porphyrin (83) we first
prepared 4-(2-chloroethyl)-2-formyl-3,S-dimethylpyrrole (76) as follows
(Seheme 1Q). Benzyl 4-(ethoxycarbonylmethyl)-3,5-dimethylpyrrole-2-
carboxylate (72) was prepared by reaction of ethyl 3-acetyl-4-oxopentanoate (71)
and the a-oximino derivative of benzyl acetoacetate (70) with zinc dust in 45%
yield. The ester group of the pyrrole (72) was easily reduced to the
hydroxyethylpyrrole (73) by diborane in 94% yield. The chlorinated pyrrole
(74) was smoothly obtained in almost quantitative yield by treatment of the
hydroxylpyrrole (73) in benzene with some excess of thionyl chloride. The
reaction was completed within 3 hours at room temperature without any base
as an acid scavenger. Traditionally base was added to remove the acid which
was formed as a by-product in the chlorination by thionyl chloride. But base
is not necessary in this reaction because the reaction with base was not
smooth and the product was obtained in poor yield (<30%). The chlorinated
pyrrole (74) was hydrogenated with 10% palladium/ carbon to give the
corresponding acid pyrrole (75) quantitatively, which was transformed to the
corresponding formyl pyrrole (76) by treating with trifluoroacetic acid and
triethyl orthoformate in 84% yield.

In Scheme 11, the 1,6-hexanedione dipyrrole (78) was prepared by
treating the B-free pyrrole (77)122 with adipoyl chloride in the presence of
tin(lV) chloride in 86% yield. The hexamethylene bispyrrole (79) was
obtained by reduction of the hexanedionedipyrrole (78) with an excess of
diborane in 87% yield. Transesterification of the ethyl ester of the dipyrrole

(79) in an excess of hot benzyl alcohol with sodium benzyloxide gave the

75

 

 

/\ 0p T BZHG

 

H Pd-C

 

 

Cl

 

76

OH H

NI
Zn/AcOI-l / \

I
W +V°W°V --——~ ~ °\/
0 o o o H '

$1104

0 o
ot/UNCHZ)(1LCI
o 0
(CH2)
Vex ixck/
o H 73 H o
32146
I—Xszlj-j
\/9 / N\ I N\ °\/
0 H 79 H o
2 OH
Z-XWHDCZ—j
/ \ / \
0V0 u u OVQ
o 80 o

H2/Pd-C

(CH2)
1" :uj; :Zfi: T
O 81 0

Schema}.

 

Na

 

 

correspond benzyl ester compound (80) (>94% yield), which was hydrogenated
with 10% palladium/ carbon to give the corresponding acid dipyrrole (81) in
97% yield. As shown in SQeme 12, the tetrapyrrole (82) was obtained by
condensation of the acid dipyrrole (81) with two equivalents of the formyl
pyrrole (76) in 88% yield. The reaction was accomplished within 30 minutes
in boiling methanol in the presence of 48% hydrobromic acid. The dimeric
porphyrin (83) was synthesized through condensation of the tetrapyrrole (82)
with two equivalents of the dibromopyrrylmethene (65) in anhydrous formic
acid in the presence of one equivalent of bromine (9% yield). According to
Sgeme 13. the dimeric porphyrin (83) was transformed to the dimeric
vinylporphyrin (84) to prepare the formyl analogue (85) and the benzochlorin
analogue (86) which have strong absorption bands in the red region of visible
light spectrum. The dimeric vinylporphyrin (84) was easily obtained by
treatement of the dimeric porphyrin (83) with DBU in 75% yield. The
reaction was completed in N ,N -dimethylformamide (DMF) within 2 hours at
80 0C. The dimeric chlorin (85) was prepared from the reaction of the dimeric
vinylporphyrin (84) with singlet oxygen (102) which was generated by
treatment of bubbling oxygen gas in the reaction solution with irradiation of
xenon lamp. The reaction was stopped when a tenth part of the
vinylporphyrin (84) was remained which was monitored by TLC and UV-vis
spectrum because longer irradiation of light gave more by-products and
chewed up the vinylporphyrin (84) by photobleaching.

DielS-Alder adduct (69 in Sche_m_e_2), initially formed from reaction of
the dimeric vinylporphyrin (84) with DMAD, was rearranged by DBU to give
the thermodynamically controlled dimeric benzochlorin (86 in Scheme} and
w. Thus, when the dimeric vinylporphyrin (84) was allowed to

react with an excess of DMAD in refluxing toluene for 5 days, followed by

78

 

 

cono COZMO
2X / \ / 1
Br N
H Br‘ H+ Br
Cl
Me M9020. COzMe

83

Scheme};

DBU

 

HO
0‘ OH ’0
\
(CH3. ”

 

 

 

W 002“: M9020 cozug
85 ‘
02/”?
I
((3sz ‘
002Mo M9020 002MB
(1) DMAD
84 (2) DBU
l)
I’mzm
9 "°
((3sz
M9020 002MB M0020

 

86

tiea
yie
on

tra

80

treatment with DBU, the desired dimeric benzochlorin (86) was obtained (27%
yield) as the major product along with a small amount of by-product in which
only one of the two vinyl groups of the dimeric porphyrin (84) was
transformed (identified by spectrophotometry).

III. RESULTS AND DISCUSSION

The sensitizers, designed, prepared and tested in this study, consist of
two carboxylic porphyrin or chlorin molecules linked by 6-carbon chain. The
synthesis of the dimeric porphyrin (83) was quite straightforward and which
was easily transformed to the dimeric vinylporphyrin (84). In proton NMR
spectrum, the newly formed vinylic structure shows an ABX spectrum.
Proton A (8~6.29) is deshielded about 52.4 Hz compared with proton B,
because of its relative proximity to the porphyrin ring. Proton X (8~8.21) is
Strongly deshielded by the porphyrin ring and is split by proton A (]~17.8 Hz)
and by proton B (]~11.4 Hz). The A proton signal is split by the X proton
(]~17.8 Hz) and by the B proton (I~1.6 Hz). The B proton signal is also split by
the X proton (I~11.4 Hz) and by the A proton (I~1.6 Hz). The coupling
constants show the characteristic of a vinyl system; the trans coupling is larger
than the cis, and the geminal coupling is very small. The 8 mesa protons
absorb in a characteristically narrow range, 8~9.946 to 8~10.138, and are
strongly deshielded by the strong aromatic ring current of porphyrin. The 4
. NH protons absorb at 8~-3.83 which are strongly shielded by the porphyrin
ring. The mass spectrum of the dimeric vinylporphyrin (84) shows the strong
molecular ion peak at m/e=1210.2. The dimeric formylmethylenylchlorin
(85) was easily prepared by treatment of the dimeric vinylporphyrin (84) with

81

singlet oxygen (‘02). In proton NMR spectrum, two formyl protons absorb at
8~9.38-8~9.54. Two hydroxyl protons are seen as a broad peak at 8~6.36,
downfield compared with the alcoholic proton (8~2.0-8~4.0). The four NH
protons are split into two peaks (each 2H) at 8-4.17 and 8~-3.88.

Diels-Alder reaction of the dimeric vinylporphyrin (84) with DMAD
was tried in several reaction conditions. The best condition was to react the
vinyl conpound (84) with a large excess of DMAD in refluxing toluene for 5
days. When the chlorin (69 in mg) formed by Diels-Alder addition was
treated with DBU, the isolated double bond tautomerized to the fully
conjugated system (86), accompanied by a red shift in the visible spectrum of
band I (from 657 to 681 nm). The proton NMR spectrum of the dimeric
benzoporphyrin (86) shows the 8 mesa protons absorb in characteristically low
field, 8~8.97 to 8~9.67. The vicinal exocyclic protons (H-73, H-74) at 8~7.42 and
8~7.81 are split by each other (I~5.6 Hz) and the other exocyclic proton (H-71) is
shown a singlet peak at 8~5.03. The splitting pattern and coupling constant
Show the characteristic of the exocyclic system in benzochlorin. The 4 NH
protons are split into two peaks (each 2H) at 8-243 and 8~-2.51.

Absorbance spectrum of the dimeric porphyrin (83) was not unusual: a
Soret band in the vicinity of 400 nm, and 4 peaks of decreasing intensity at
498, 533, 568 and 621 nm (in CH2C12; Figure 7). The dimeric vinylporphyrin
(84) showed only a small red-shift from the peaks obtained with the dimeric
porphyrin (83) as shown in Figure 7. The absorbance spectrum of the dimeric
formylmethylenylchlorin (85) showed red-Shifted absorption of band I and
the remarkable increase of the intensity in the red bands as shown in Figure 8
and Table 4. The absorption spectrum of the dimeric benzoporphyrin (86)
showed more (20 nm) red-shift than that of the dimeric

formylmethylenylchlorin (85) with almost same intensity in the red region.

82

+2 .009

T)

 

D0

\ .

DUI
HO
C0

 

 

 

+0 .009

 

 

 

399.9 100.0(NH/DIU.)
[ 700.0HH

' NH
700.0

Figure 7. UV-vis absorption spectra of dimeric chloroethylporphyrin (83; -)
and dimeric vinylporphyrin (84; °°°°°° ) in CH2C12.

 

 

 

 

   

 

 

 

+2.999 r *r . i
9.599
(n/aru.>”
Q
A”
'- g I. q.
A\ ‘ll
\ktty‘ift. )
+9.99n , I “ - N"
299.9 100.0(NN/DIU.) 800.0
[ 800.0Nfl 9.9999]

 

Figure 8. UV-vis absorption spectra of dimeric chloroethylporphyrin (83; —),

dimeric vinylporphyrin (84; ------ ), dimeric formylmethylenylchlorin
(85; .. . .), and dimeric benzoporphyrin (86; --) in CH2CI2.

Table 4. UV-vis absorption spectral data of dimeric chloroethylporphyrin
(83), vinylporphyrin (84), formylmethylenylchlorin (85) and
benzoporphyrin (86) in CH2C12.

 

 

 

 

 

 

Absorbance (nm) in CH2C12
Compound Soret IV III II I
83 400 498 533 568 621
84 402 502 539 570 625
85 387 - 570 670 662
86 417 - 580 620 681

 

 

 

 

 

 

 

 

This strong absorbance in the longer wavelengths may be advantageous in
eradication of larger tumors and utilization of inexpensive laser sources.
Fluorescence lifetimes of dimeric porphyrins were approximately 15:1 ns, a
result also obtained with porphyrin monomers, e. g., hematoporphyrin. In
contrast, the ether dimers found in HPD showed a shorter lifetime, 7 ns.
These results demonstrate the absence of fluorescence-quenching ring-ring
interactions in the dimeric porphyrins linked by a hexamethylene bridge.
The dimeric porphyrins were short term sensitizers in viva. Optimal timing
between injection and irradiation in viva (mouse tumor system) was 3 hr for
the active products. In contrast, Photofrin-II allows a 24 hr interval.
Persistence in plasma of the dimeric porphyrins was substantially less than
that of HPD. The determinants of persistence of dyes in neoplastic cells are
not yet fully elucidated. Biological studies of the dimeric porphyrins in vitra

and in viva were not entirely carried out.

IV. EXPERIMENTAL

E l a -4-ox ntan ate

Anhydrous potassium carbonate (415 g, 3 mol) and potassium iodide
(99.6 g, 0.6 mol) were added to a solution of 2,4-pentanedione (308 mL, 3 mol)
and ethyl chloroacetate (320 mL, 3 mol) in 2-butanon (1 L). The reaction
mixture was carefully heated to reflux for 5 hours because of its exothermic
character, and then diluted with acetone to precipitate salt. The solid was
filtered off and washed with acetone. The filtrates were concentrated under
vacuum and the residual oil was distilled under reduced pressure to yield the
title compound as colorless liquid (260 g, 50.4%): b.p. 128-131 oC/8-10 mm; 1H-
NMR (CDC13) 8 1.09 (3H, t, ~OCH2§I_'13), 2.11 (6H, s, cogs), 2.72 OH, 5,
-C0§fl2), 3.10 (1H, t, -CH), 3.96 (2H, q, -O§_I-12CH3) ; M5 for C9H14O4, found
m/ e 186 (M+).

WW
Ethyl acetoacetate (1280 mL, 10 mol) and benzyl alcohol (1040 mL, 10

mol) were mixed and heated to boil away formed ethyl alcohol. The residual
oil was distilled under reduced pressure to give the title compound as
colorless liquid (1693 g, 88.2%): b.p. 156-159 0C/ 10 mm; 1H NMR (CDC13) 8 2.26
(3H, s, QHgCO), 3.50 (2H, s, CECO), 5.19 (2H, s, C_H2C6H5), 7.37 (5H, m,
phenyl protons); MS for C11H1203, found m/ e 192 (M+).

85

14- etho arbon lmeth l- dimeth 1 ole-Z-carbox late

Benzyl acetoacetate (70) (192 g, 1 mol) dissolved in acetic acid (200 mL)
was cooled in an ice bath and an ice cold solution of sodium nitrite (76 g, 1.1
mol) in water (100 mL) was added dropwise over 2 hours. The resulting cold
solution of benzyl a-oximinoacetoacetate was added dropwise, along with
zinc dust (200 g) in small portions, to a stirred solution of ethyl 3-acetyl-4-
oxopentanoate (71) (186 g, 1 mol) in acetic acid (350 mL). Near the end of the
addition, the temperature of reaction mixture reached above 80 0C and then
the reaction mixture was refluxed for an additional one hour. After the
reaction was completed, the mixture was poured into a large amount of water
to result solid product. The resulting solid was collected by filtration and
washed repeatedly with water. The filtered cake was dissolved in
dichloromethane and zinc was filtered off and rinsed with dichloromethane.
The filtrate was evaporated to give the solid pyrrole which was crystallized
from methanol and water to give the title compound as a white sparkling
power (141.8 g, 45%): mp. 79-80 0C; 1H NMR (CDC13) 8 1.23 (3H, t, -OCH2_(;I;I3),
2.21 (3H, s, 3-Me), 2.29 (3H,s, S-Me), 3.38 (2H, s, CH2C02C2H5), 4.11 (2H, q,
-O§L-I_2CH3), 5.38 (2H, s, -O_(_Z_I-I2Ph), 7.39 (5H, m, phenyl protons), 8.93 (1H, br 5,
NH); MS for C13H21NO4, found m/ e 315 (M1).

1 2-h th 1 ime h l 01 2 arbo lat

Sodium borohydride (8 g, 0.2 mol) was added to a solution of benzyl 4-
(ethoxycarbonylmethyl)-3,5-dirnethylpyrrole-2-carboxylate (72) (31.5 g, 0.1 mol)
in dry tetrahydrofuran (150 mL) and cooled to 10 0C with stirring in an ice
bath. To the reaction mixture, boron trifluoride etherate (35 mL, 0.28 mol)
was added dropwise under nitrogen such that the temperature of the reaction

mixture was maintained 1513 0C. After the addition, the reaction mixture was

stirred for an additional 30 minutes in the ice bath and 2 hours at room
temperature or until the reaction was completed, which was monitored by
TLC using chloroform. Methanol (50 mL) was careftu added to the reaction
mixture until the vigorous effervescense ceased and the reaction mixture was
diluted with dichloromethane (150 mL) and then with water (300 mL). The
organic layer was separated, washed with hydrochloric acid (0.5N, 100 mL)
and finally twice with water (100 mL). The solvents were evaporated under
reduced pressure after methanol (50 mL) was added. The resulting white solid
was crystallized from dichloromethane and hexane to give the title
compound as pale bluffy needles (25.7 g, 94%): mp. 115-116 0C ;1H NMR
(CDC13) 8 1.92 (1H, br s, OH), 2.21 (3H, s, 3-Me), 2.31 (3H, S, 5-Me), 2.65 (2H, t,
fiCHon), 3.65 (2H, t, -CH2QH_2_OH), 5.30 (2H, 5, -OC_H2_Ph), 7.39 (5H, m,
phenyl protons), 9.19(1H, br 5, NH) ; M5 for C15H19NO3, found m/ e 273 (M"').

14- 2-chl r th 1- 5- imeth l ole-2-carbo late

Benzyl 4-(2-hydroxyethyl)-3,5-dimethylpyrrole-2-carboxylate (73) (54.6 g,
0.2 mol) was dissolved in dry benzene (1 L) with warming. The
homogeneous solution was cooled down to room temperature and fresh
thionyl chloride (29.2 mL, 0.4 mol) was added under nitrogen. The reaction
was accomplished by stirring for 3 hours at room temperature without any
base as an acid scavenger. The solvent was evaporated to dryness under
vacuum, and the residue was chromatographed through a short flash column
of silica gel with dichloromethane. A trace amount of unreacted starting
material (73) and some impurities remained in the silica gel and only the title
compound (74) was eluted by dichloromethane. The eluates were combined

and evaporated under reduced pressure. The resulting residue was

87

crystallized from dichloromethane and hexane to give the title compound as
ivory-white fluffy crystals (57.2 g, >99%): m.p. 119-120 0C ;1H NMR (CDC13) 8
2.20 (3H, s, 3-Me), 2.28 (3H, s, 5-Me), 2.83 (2H, t, Q12CH2CI), 3.51 (2H, t,
mflgfl), 5.29 (2H, s, -OC_I_-I_2Ph), 7.39 (5H, m, phenyl protons), 8.88 (1H, br 5,
NH); MS for C15H13N02Cl, found m/ e 291 (M+).

1r hl- imethl 12-arb lica'd

Benzyl 4-(2-chloroethyl)-3,5-dimethylpyrrole-Z-carboxylate (74) (29.2 g,
0.1 mol) was dissolved in freshly distilled tetrahydrofuran (400 mL), and then
10% palladium/ carbon (1 g) and triethylamine (10 drops) were added. The
reaction mixture was stirred under hydrogen (1 atm., room tempersture)
until hydrogen uptake ceased. After hydrogenation, palladium/ carbon was
filtered off and washed further with tetrahydrofuran. The filtrates were
combined and evaporated under vacuum to give the title compound as a
white-gray powder (20.0 g, >99%): m.p. 114-116 0C; 1H NMR (CDC13) 8 223
(3H, s, 3-Me), 2.29 (3H, S, 5-Me), 2.85 (2H, t, CH2CH2CI), 3.51 (2H, t,
CHflgCl), 8.88 (1H, br 5, NH), 11.20 (1H, br 5, -COOH); M5 for C9H12NO2C1,
found m/ e 201 (M+).

r h12-frml- imthl l
4-(2-Chloroethyl)-3,5-dimethylpyrrole-Z-carboxylic acid (75) (10.1 g, 0.05
mol) was dissolved in trifluoroacetic acid (50 mL) at 40 0C and triethyl
orthoformate (16.7 mL, 0.1 mol) was added in one portion. The reaction
mixture was stirred further for 5 minutes at 40 oC and quenched by adding
water slowly with gentle stirring to give precipitated oil which soon
solidified. The resulting solid was collected by filtration and dissolved in

ethanol (100 mL). To the ethanolic solution, ammonium hydroxide (2N, 70

88

mL) was slowly added with stirring and after 10 minutes, water (150 mL) was
added to precipitate product. The resulting solid was collected by filtration
and chromatographed on silica gel with 0.5% methanol in dichloromethane
and then crystallized from ethanol and water to give the title formyl pyrrole
(7.8 g, 84%): m.p. 144-148 °C; 1H NMR (CDC13) 8 2.26, 227 (3H each, s, 3, 5-
Me), 2.83 (2H, t, CH2CH2C1), 3.51 (2H, t, -CH2$ll2C1), 9.46 (1H, S, -CI_-IO), 9.56
(1H, br 5, NH); MS for C9H12NOC1, found m/ e 185 and 187 (M+).

Diethyl eximinomalonate.
Diethyl malonate (160.7 g, 1.0 mol) was dissolved in glacial acetic acid

(200 mL) and then cooled in an ice bath. A saturated aqueous solution of
sodium nitrite (207 g, 3.0 mol) was added dropwise with stirring in an ice bath
and the temperature was controlled below 20 °C. After addition the reaction
mixture was stirred in an ice bath for another one hour. The light orange

oxime solution was kept at low temperature and used immediately.

E l . im 1 ol 2 ar la .

A solution of 2,4-pentanedione (100.1 g, 1.0 mol,)in glacial acetic acid
(200 mL) was heated, and at 80 °C anhydrous sodium acetate (246 g, 3.0 mol)
and zinc dust (197 g, 3.0 mol) were added with vigorous stirring. At 95 °C the
diethyl oximinomalonate, prepared before, was added dropwise with
vigorous stirring and the temperature was maintained between 95 and 105 °C.
After heating to 100-105 0C for an additional 30 minutes, the reaction mixture
was poured with stirring into ice-water mixture (3 L). The crude product was
collected by filtration, washed with water, and then dissolved in hot 95%
ethanol (1 L). After filtration of the hot mixture to remove the zinc dust, the

filtrate was concentrated to 300 mL, poured into ice-water mixture (1.5 L) to

89

precipitate product. The solid product was collected by filtration and
recrystallized from 95% ethanol to afford the title compound (108.6 g, 65%
yield): m.p. 124-125 °C; 1H NMR (CDC13) 8 1.33 (3H, t, '0CH2QL‘IQ), 2.23, 2.29
(3H each, s, 3, S-Me), 4.27 (2H, q, -OC_H2CH3). 5.77 (1H, s, 4-H), 8.85 (1H, br 5,
NH); M5 for C9H13N02, found m/ e 167 GM“).

1 -Bis - ethox carbon 1-2 4-dimeth l ole- 1-1 6—hexanedi ne

Ethyl 3,5-dimethylpyrrole-2-carboxylate (77) (16.7 g, 0.1 mol) was
dissolved in a mixture of dry dichloromethane (150 mL) and dry
nitromethane (100 mL) with heating, and adipoyl chloride (7.3 mL, 0.05 mol)
was added in an ice bath under nitrogen. To the cold reaction mixture,
tin(IV) chloride (17.5 mL, 0.15 mol) was added dropwise in the ice bath over
30minutes with stirring. The reaction mixture was stirred for an additional 4
hours at room temperature, poured into ice/ water (200 mL), acidified with
concentrated hydrochloric acid, and stirred for 15 minutes to complete the
hydrolysis of the tin(IV) complex. The precipitated mass of product was
collected by filtration, washed alternately with water and dichloromethane,
and finally with methanol (collected separately). After drying, the solid
weighted 37.8 g (73.5% yield). Evaporation in of the organic phases from the
filtrates afforded a second crop of 6.3 g (123%). Total 44.1 g (85.8%).

For analysis, a sample was recrystallized from tetrahydrofuran and
methanol: 1H NMR (CDC13) 8 1.27 (6H, t, -OCH2§I_i;), 1.57 (4H, m, CI-Iz), 2.42,
247 (6H each, s, 2, 4-Me), 270 (4H, t, -CO§I_-I;), 4.22 (4H, q, OQH2CH3), 11.73
(2H, br 5, NH); MS for C24H32N206, found m / e 444 (Mt).

9O

Bi e o arbon 1 24-dimeth l ole-3- l-16-hexane

Sodium borohydride (8 g, 0.2 mol) was added to 1,6-bis[5-
(ethoxycarbonyl)-2,4-dimethylpyrrole-3-yl]-1,6-hexanedione (78) (222 g, 0.05
mol) dissolved in dry tetrahydrofuran (100 mL). The reaction mixture was
cooled to 10 0C with stirring in an ice bath and treated with dropwise boron
trifluoride etherate (35 mL, mol) under nitrogen such that the temperature of
the reaction mixture was maintained 1513 °C. The reaction mixture was kept
stirring for additional 30 minutes in the ice bath and 3-4 hours at room
temperature until the reaction was completed which was monitored by TLC
using chloroform. The reaction mixture was poured into a mixture of ice (200
mL), hydrochloric acid (IN, 50 mL) and chloroform (200 mL). The organic
phase was washed with hydrochloric acid (0.5N, 100 mL) and then with water
and dried over anhydrous sodium sulfate. Methanol (50 mL) was added to
the organic solution and then the solvents were removed under reduced
pressure until the product crystallized out. The solids were collected by
filtration, washed with methanol, and dried to give the title compound (25.1
g, 82.9%). Evaporation of the organic filtrates gave a further 1.2 g (4.0%).

For analysis, a sample was recrystallized from dichloromethane and
methanol: 1H NMR (CDCl3) 8 1.31, 1.38 (4H each, m, CH2), 1.32 (6H, t,
-OCH2g;I-_I_;), 2.15, 2.23 (6H each, s, 2, 4—Me), 2.31 (4H, t, CH2), 4.27 (4H, q,
-O§Ij_2_CH3), 8.66 (2H, br 5, NH); MS for C24H36N 204, found m/ e 416 (Mi').

1 ‘B' - 1 car n 1-24- imeth l l 3- l-1 hexane

After benzyl alcohol (150 mL) was heated up to 180 0C to remove
moisture, 1,6-bis[5-(ethoxycarbonyl)-2,4-dimethylpyrrole-3-yl]-1,6-hexane (79)
(41.6 g, 0.1 mol) was added. The reaction mixture was heated up to boiling for

10 minutes to drive off water. To this hot homogeneous solution, a fresh

91

saturated solution of sodium in dry benzyl alcohol (10 mL) was cautiously
added in small (1 mL) portions under nitrogen until the evolution of ethanol
ceased. Further portions were added every several minutes until the
exchange was completed when the boiling point had again risen above 200
°C. Heating was continued to reflux for 10 minutes after the effervescence
subsided. The hot reaction mixture was poured cautiously into a
magnetically stirred solution of acetic acid (20 mL) in methanol (500 mL), and
water was then added until crystallization was completed. The light pinkish
solid was collected by filtration, washed with 50% aqueous methanol and
dried to give the title compound (50.9 g, 94.3%).

For analysis a sample was recrystallized from tetrahydrofuran and
methanol: m.p. 95-97 °C; 1H NMR (CDC13) 8 1.30, 1.39 (4H each, m, CH2),213,
2.24 (6H each, s, 2, 4-Me), 230 (4H, t, CH2), 5.27 (4H, s, -CI-_I2C6H5), 1.36 (10H, m,
phenyl protons), 8.56 (2H, br 5, NH); M5 for C34H40N204, found m/ e 540 (M+).

. B' . . ar-on 1-24--'°m 1- ol- 1-1 6-hexane :

1,6-Bis[5-(Benzyloxycarbonyl)-2,4-dimethylpyrrole-3-yl]-l,6-hexane (80)
(22.5 g, 0.05 mol) was dissolved in freshly distilled tetrahydrofuran (400 mL)
containing 10 drops of triethylamine. 10% Palladium/ carbon (1 g) was added
and the reaction mixture stirred under hydrogen (1 atm., at room
temperature) until hydrogen uptake ceased. The catalyst carbon was filtered
off and rinsed with tetrahydrofuran. Evaporation of filtrates gave the title
compound as a light gray power (17.5 g, 97%): m.p. 89-90 °C; 1H NMR (CDC13)
8 1.32, 3.42 (4H each, m, CH2), 220, 231 (6H each, s, 2, 4-Me), 238 (4H, t, CH2),

92

8.73 (2H, br 5, NH), 11.21 (2H, br 5, -COOH); M5 for C20H23N 204, found m/ e
360 (M+).

 

yllhgane bromide (82)
1,6-Bis[5-(Hydroxycarbonyl)-2,4-dimethylpyrrole-3-yl]-1,6-hexane (81)

(7.20 g, 0.02 mol) and 4-(2-chloroethyl)-2-formyl-3,5-dimethylpyrrole (76) (7.42

g, 0.04 mol) were suspended in methanol (100 mL) and heated up to boiling.
Hydrobromic acid (48%, 16 mL) was carefully added in one portion (vigorous
forming), and the red-orange product was immediately formed. After the
reaction was accomplished by heating for 30 minutes, the reaction mixture
was transfered into a beaker and then allowed to stand for 2 hours at room
temperature. The resulting orange fluffy solid was collected by filtration,
rinsed with slightly acidified water containing small amount of hydrobromic
acid, and dried in air to give the title compound (13.1 g, 88%).

For analysis, a sample was recrystallied from dichloromethane and
hexane : 1H NMR (CDC13) 8 1.28, 1.40 (4H each, br s, CH2), 2.23, 228 (3H each,
s, -CH3), 239 (4H, t, CH2), 263, 2.65 (6H each, s, CH3), 286 (4H, t, figCHzCl),
3.53 (4H, t, -CH2§I;I;C1), 7.04 (2H, s, methine), 13.03, 13.10 (2H each, br 5, NH).

1.2319 8-(2-ghlorgthy12-1 3,17-eis(2-methoxycarmnylethyl )-S I7,12,1S-tetra-

m l h °n-2- l hexane
1,6-Bis[4'-(2-chloroethyl)-3,3',5,5'-tetramethyl-2,2'-dipyrrylmethenium-
4-yl]hexane bromide (82) (3.73 g, 5 mmol) and 5,5'-dibromo-3,3'-bis(2-
methoxycarbonylethyl)-4,4'-dimethyl-2,2'-dipyrrylmethenium bromide (65)
(5.83 g, 10 mmol) were suspended in formic acid (98-100%, 90 mL) and the

mixture was heated up to 80 °C in an oil bath. At this temperature, bromine

93

(0.52 mL, 10 mmol) was added in one portion and the reaction mixture was
refluxed for 2 hours. The solvent was then allowed to boil off and the residue
was dried completely with further heating in the oil bath up to 130-140 °C
during which time the porphyrin was formed. Methanol (100 mL) and
concentrated sulfuric acid (5 mL) were added to the residue, and after 10
minutes triethyl orthoformate (12 mL) was added. After standing overnight,
protected from moisture, the solution was diluted with dichloromethane and
the tar residue was filtered off by passing the solution through glass wool.
The solution was neutralized with saturated aqueous sodium bicarbonate.
The organic layer was separated, washed twice with water and dried over
anhydrous sodium sulfate. The solvent was removed under vacuum to
dryness and the resulting crude product was chromatographed on silica gel
column with 1% methanol in dichloromethane as eluent. A dark
nonfluorescent forerun was discarded. The major reddish fractions
containing dimeric porphyrin were collected and crystallized from
dichloromethane and methanol to give the title compound as red-brown
sparkling crystals (0.58 g, 9%): m.p. > 248 °C (decomp.) ; 1H NMR (CDC13) 8
-3.86 (4H, br 5, NH), 1.90, 2.32 (4H, br s, CH2), 3.14, 3.26 (4H each, t,
CH2§H_2_C02), 3.42, 3.52, 3.56, 3.58, 3.63, 3.65 (6H each, s, ring Me, OMe), 4.03
(4H, t, 2-CH2), 4.12 (4H, t, CH2§fi2Cl), 4.22 (4H, t, §_I-_I2CH2C1), 4.42, 4.54 (4H
each, t, CH2CH2CO2), 9.95, 9.99, 10.01, 10.01 (2H each, s, meso H); UV-vis (in
CH2C12) Amax (SM) 621 nm (5,000), 568 (7,000), 533 (10.000), 498 (14,000), 400
(178.000); M5 for C74H34N303C12, found m/ e 1283 (M+).

94

1 Bi 1 17-bis 2-methox carbon leth 1-3 71218-tetrameth l-8-vin l-
mgphm’n-Z—yllhexane (84)

1,8-Diazabicyclo[5.4.0]undec-7-ene (1 mL) was added to 1,6-bis[8-(2-
chloroethyl)-13,17-bis(2-methoxycarbonylethyl)-3,7,12,18-tetramethylporphy-
rin-Z-yllhexane (83) (154 mg, 0.12 mmol) dissolved in dry N,N-
dimethylformamide (30 mL). The reaction mixture was heated in an oil bath
at 80 0C for 2 hours and then cooled to room temperature. To the reaction
solution, water was added with stirring until the product precipitated. The
precipitated solid was collected by filtration on a bed of Celite and rinsed with
excess water, finally with a small amount of methanol. The product on Celite
was extracted with dichloromethane and the solvent was removed under
vacuum. The resulting residue was chromatographed on silica gel column
with 0.5% methanol in dichloromethane as eluent [the title compound (84)
moves slower than the starting compound (83) on the silica gel column], and
crystallized from dichloromethane and methanol to give the title compound
(109 mg, 75%): m.p. > 248 0C (decomp.); 1H NMR (CDC13) 5 -3.83 (4H, br s,
NH), 1.90, 233 (4H each, m, CH2), 3.14, 3.22 (4H each, t, CI-IzggCOz), 3.41, 3.49,
3.58, 3.61, 3.63, 3.63 (6H each, 5, ring Me, OMe), 4.00 (4H, t, 2-CH2), 4.20, 4.40 (4H
each, t, ($20-1sz, 6.10, 6.30 (2H each, d, -CH=§;I-_Ig), 8.22 (2H, dd, -§I;I=CH2),
9.94, 9.96, 9.98, 10.14 (1H each, s, meso H); UV-vis (in CH2C12) Amax (819)625
nm (4,000), 570 (8,800), 539 (12,000), 502 (14,000), 402 (170,000); MS for
C74H32N303, found m/ e 1211 (M+).

1 i f rm lmeth len 1-7-h dr -1 17-bis 2-methox car n l l-
2 t amthl lrin-2-lhexan
1,6-bis[13,17-bis(2-Methoxycarbonylethyl)-3,7,12,18-tetramethyl-8-vinyl-
porphyrin-Z-yllhexane (84) (121 mg, 0.1 mmol) was dissolved in

95

dichloromethane (100 mL) with pyridine (0.5 mL) and oxygen gas was bubbled
in the reaction solution with irradiation of xenon lamp (200 W). The
irradiation was stopped when a tenth part of the starting vinyl porphyrin (84)
was remained which was monitored by TLC. After the reaction, the reaction
mixture was neutralized with diluted acetic acid. The organic layer
containing the product was washed with water, dried over anhydrous sodium
sulfate, and evaporated to dryness under vacuum. The resulting residue was
chromatographed on silica gel with 1-1.5% methanol in dichloromethane to
give the title compound (54 mg), 47% yield based on reacted the compound
(84): 1H NMR (CDCL3) 8 -4.17, -3.88 (2H each, br 5, NH), 1.14 (6H, s, 7-Me), 1.81,
2.20 (4H each, m, CH2), 3.01, 3.11 (4H each, t, CI-12_C_I-12CO2), 292, 2.94, 3.17, 3.17,
3.18, 3.18, 3.57, 3.58, 3.61, 3.61 (3H each, 5, ring Me, OMe), 3.70 (4H, t, 2-CH2),
3.94, 4.16 (4H each, t, C_I_-I_2_CH2C02), 6.36 (2H, br s, OH), 8.23 (2H, br s, =QI-_I-
CHO), 9.38, 9.39, 9.51, 9.54 (1H each, s, meso H), 9.83 (2H, br s, -CHO); UV-vis
(in CH2C12) 1mm, (8“) 662 nm (71.000), 605 (22900), 570 (30,100), 387 (193,000);
MS for C74ngNgO12, found m/ e 1275 (M+).

’1 ,§;Bi§] fill-big memogyearbonyl )-1 SJ 7-bi§( 2-metheyycarhenylghyl )-

S,7,1Alkteggameghyl-Zfl-dih r nz h ' -2- l h an
Dimethyl acetylenedicarboxylate (DMAD) (5 mL, 40 mmol) was added

to 1,6-bis[13,17-bis(2-methoxycarbonylethyl)-3,7,12,18-tetramethyl-8-
vinylporphyrin-Z-yl]hexane (84) (84.7 mg, 0.07 mmol) dissolved in dry
toluene (40 mL). The reaction mixture was refluxed under nitrogen in the
dark for 5 days. After the Diels-Alder reaction was completed, the solvent was

evaporated and the residue was further dried under high vacuum to remove

96

toluene and the remaining trace of DMAD. A few drops of 1,8-
diazabicyclo[5.4.0]undec-7-ene were added to the DielS-Alder adduct (69)
dissolved in dichloromethane (35 mL), which is isolable but not isolated. The
rearrangement reaction occured immediately. The reaction mixture was
poured into 2N hydrochloric acid and the product was extracted with
dichloromethane. The organic layers were combined, washed with water and
brine, and dried over anhydrous sodium sulfate. Evaporation of the solvent
gave a residue which was purified by preparaive thick layer plates (silica gel)
eluted with 1% methanol in dichloromethane. The product was extracted
from silica gel and crystallized from dichloromethane and petroleum ether to
give the title compound (28.2 mg, 27%): 1H NMR (CDC13) 8 -2.51, -2.43 (2H
each, br 5, NH), 1.78 (6H, s, exocyclic ring Me), 1.88, 2.24 (4H each, m, CH2),
288, 3.33, 3.43, 3.47, 3.61, 3.62, 3.97 (6H each, 5, ring Me, OMe), 3.09, 3.18 (4H
each, t, CH2§_I_-I_2C02, 4.12, 4.31 (4H each, t, figCHzCOfl, 5.03 (2H, s, H-7'), 7.42,
7.81 (2H each, d, H-73,H-74), 8.97, 9.38, 9.67, 9.67 (1H each, s, meso H); UV-vis
(in CH2C12) Am (8”) 681 nm (27,000) 620 (8,200), 580 (15,000), 417 (70,000), 353
(42,300); MS for C35Hg4N3016, found m/ e 1495 (M+).

CHAPTER 4
SYNTHESES AND PROPERTIES OF
CATIONIC PORPHYRIN AND BENZOCHLORIN DERIVATIVES

I. INTRODUCTION

In preliminary studies, a cationic photosensitizer has shown itself to be
a non-traditional photodynamic sensitizer in that it exhibits an extremely
short triplet state formation in solution (approx. 20 nsec).50:51 It seems
unlikely that its PDT effect is initiated by type II reactions (via singlet oxygen,
102). To study the mechanisms of action of cationic photosensitizers, we
designed and prepared several cationic photosensitizer derivatives.

To prepare porphyrins containing ammonium group, we first
synthesized some porphyrins containing ester group (87, 97, 124, 125) which
were hydrolyzed, chlorinated with oxalyl chloride and reacted with N,N-
dimethylethylenediamine to give the corresponding derivatives containing
dimethylamine group (90, 100, 130, 131), which were treated with
iodomethane to yield the corresponding trimethylammonium group (91, 101,
132, 133). Also we introduced "oxo" group on porphyrin ring to prepare some
porphyrinones (104, 136) containing trimethylammonium group which
possess better absorption character and 20 nm red-shift in the visible spectrum
than the corresponding porphyrins (101, 132, 133).

97

98

In 1978, Johnson et al.124 reported the synthesis of the first
benzochlorin (C), after cyclization of nickel mesa-(Z-formylvinyl)
octaethylporphyrin (B), obtained from nickel(II) complex of
octaethylporphyrin (A) via a three step, low yield procedure. Successive
formylation and Wittig reaction of the nickel octaethylporphyrin (A) gave the
mesa-vinyl derivative (E) (see Scheme 14). A second formylation gave
compound (B) which was treated with mineral acid for cyclization to give
nickel(II) octaethylbenzochlorin (G) in 22% yield. Recently, Smith and co-
workerslzsrlz" improved this pathway, utilizing a modified Vilsmeier reagent
[3-(dimethylamino)acrolein and phosphoryl chloride; (3-DMA/POC13)] which
gave access to the formyl derivative (B) in one step, starting from (A).

Cyclization generated, once again, the nickel benzochlorin (G).

R O

A MaNi, RsH F M==2H
B M=Ni, FI=CHCHCHO G M=Ni
C M=2H, R=CHCHCH20H

D M=2H, R=CHCHC02EI

E MaNi. FI=CHCH2

99

Alternatively, Morgan et al.129 showed that cyclization of the mesa-(3-
hydroxypropenyl)octaethylporphyrin (C), obtained after reduction of mesa-[B-
(ethoxycarbonyl)vinyl]octaethylporphyrin (D), gives also the target
benzochlorin (F) in 36% yield (Scheme 14). Benzochlorins possess an intense
absorption at 658 nm, whereas addition of a metal, into the aromatic cavity, is
characterized by a 15 nm red shift in the visible spectrumJ7-5v125r129

In 1984, our group, in studying reversible modification of formyl
peripheral substituents, reported that protonated Schiff bases (imines) of
”chlorin-type" compounds (i.e. pyrrolidinium salt (H) are characterized by an
unusual red shift of the absorption maxima in the visible region (up to 800

nm).58

05”"

G _
OH

CSH11

Recently, Skalkos et al.69 reported the synthesis of the iminium salts
from the reaction of metallo benzochlorins with the Vilsmeier reagent
(DMF/ POC13). The iminium salts are very stable cationic adducts,
characterized by a strong red shift (around 100 nm) of the absorption maxima
in the visible region of the electromagnetic spectrum.

100

The previous observations prompted us to investigate the syntheses of
cationic porphyrin derivatives by introduction of trimethylammonium
group on porphyrins or by reactions of benzochlorins with the Vilsmeier

reagent.

IL SYNTHESES

Several rational approaches toward the preparation of cationic
porphyrin derivatives were empoyed by total syntheses of target materials or
modifications of precusor porphyrins. Five porphyrins (87, 97, 124, 125, 137)
were chosen for investigation.

As shown in Seheme IS, ethyl 3,7-diethyl-2,8,13,17,18-
pentamethylporphyrin-l2-propionate (87), prepared before by our group, was
hydrolyzed by heating on a steam bath for 6 hours in trifluoroacetic in the
presence of hydrochloric acid, and then chlorinated by oxalyl chloride in
dichloromethane for one hour at room temperature, and then condensed
with N,N-dimethylethylenediamine in dichloromethane for one hour at
room temperature to give aminoporphyrin (90) in 80% yield which was
purified on silica gel column, using methanol-dichloromethane (15:85) as
eluant. A cationic porphyrin (91) containing trimethylammonium group was
prepared by treatment of the aminoporphyrin (90) in methanol-
dichloromethane (10:90) with an excess of iodomethane for 5 hours at room
temperature.

To prepare other two cationic porphyrin derivatives (101) in meme
11) and(104 in Sgheme IS), the porphyrin (97) was synthesized as shown in
Seheme 12 Two dipyrrylmethenes, "north" dipyrrylmethene (93) and

101

 

 

 

91

 

102

"south" dipyrrylmethene (96), were refluxed together in anhydrous formic
acid in the presence of one equivalent of bromine to form the porphyrin (97)
in 8.5% yield, after purification on silica gel column. This low yield is most
likely due to the presence of a withdrawing group which deactivates the
cyclization.

Dipyrrylmethene (96) was easily prepared from ethoxycarbonyl
dipyrrylmethane (94) as follows. The ethoxycarbonyl dipyrrylmethane (94)
was refluxed for one hour in ethanol with 40% aqueous potassium hydroxide
for hydrolysis. The obtained acid dipyrrole (95) was treated in anhydrous
formic acid with an excess of bromine for decarboxylation and bromination to
give the dipyrrylmethenium bromide (96) as shown in Scheme 16-

The other dipyrrylmethene (93) was obtained by condensation of the
acid pyrrole (7 5) and the formyl pyrrole (92) in hot methanol with
hydrobromic acid in 92% yield. The two pyrroles (75 and 92) were respectively
prepared as Shown in Scheme 10 and gheme 21.

As Shown in Scheme 17, the porphyrin (97) was transformed to the
aminoporphyrin (100) as follows. The porphyrin (97) was refluxed for one
hour in pyridin with 5% aqueous potassium hydroxide for hydrolysis (in this
case, the ester group directly attached on porphyrin ring can be hydrolyzed
only in severer condition due to stabilization by aromatic porphyrin ring.)
which was monitored by TLC, to give the acid vinylporphyrin (98). Without
purification, the obtained acid porphyrin (98) was treated for one hour at
room temperature with oxalyl chloride in dry dichloromethane for
chlorination. The dried chlorinated porphyrin (99) was directly treated for
one hour at room temperature with an excess amount of N ,N-

dimethylethylenediamine in dry dichloromethane to give aminoporphyrin

103

 

 

 

 

 

 

o
w + K / \ / \
H R
0 002 OHC i3 02c ii i—i 6023
75 92 94 a. CH CH3
L fir J ”C95 R-H 2
48% HBr 1) KOH
MeOH, A 2) Bray/HCOOH
it l,
0025: c:
/ / / /
N
H B!" H" Bf H Br- fi+ Br
93 96
L J
“K
1) Bra/HCOOH
2) 02
I!
5:020 Cl
97

104

 

 

 

EtOOC Cl HOOC
KOH/Py
97 98
OICI
O Cl
NH/\N/
0 v
0 \ Cl
/
HzN/VNM‘Z
100 99
is
N! -
o NFL/T \\ I
/
101

105

(100). The cationic porphyrin (101) was then prepared by treatment of the
aminoporphyrin (100) with iodomethane as described before.

The cationic porphyrinone (104) was prepared as described in Selleree
IS. The intermediate porphyrinone (102), made by oxidation of the porphyrin
(97) with osmium tetroxide and followed by acid-catalyzed pinacolic
rearrangement, was hydrolyzed with potassium hydroxide in pyridine,
chlorinated with oxalyl chloride and condensed with N,N-
dimethylethylenediamine to give the aminoporphyrinone (103) which was
treated with an excess amount of iodomethane as described before to give the
cationic porphyrinone (104). .

In order to investigate relative PDT efficacy of cationic sensitizers with
lipophilic character, two porphyrins (124) and (125) were synthesized as
shown in Scheme 19. Dipyrrylmethenes (115) and (116), which provide the
lipophilic character to the porphyrins (124) and (125), were respectively
condensed with dipyrromethene (123), to form the porphyrins (124) and (125)
in 12-14% yields, after purified by chromatography on silica gel with
dichloromethane-hexane (2:1).

As shown in Scheme 20, the dipyrromethanes (115) and (116) were
prepared as follows. B—Free pyrrole (77) was treated for 2 hours at around 10 0C
with octanoyl chloride in the presence of tin(IV) chloride to obtain
octanoylpyrrole (105) in almost quantitative yield. The octanoylpyrrole (105)
was reduced to octylpyrrole (106) in 94% yield with an eimess of diborane,
which was transesterificated to the corresponding benzyl ester pyrrole (107) in
an excess amount of benzyl alcohol in the presence of sodium benzyloxide in
85% yield. The pyrroles (107) and (108) were treated for one hour in hot acetic
acid with lead tetraacetate to give acetoxymethylpyrroles (109) and (110)
respectively in 95-96% yields, which were separately treated for one hour in

106

102

EtOOC

(I) 0504
(2) H+

 

Cl

97

KOH/Py

 

Mel

 

/\
103

107

 

 

 

/ / + / /
Br H Br- H + Br :1. 3,.“ 3+
115 n=5 123
116 ”:8
\F .J
TF
(1) HCOOH, Brz
(2) Air-oxidation
ll
COfifl
Co on
124 n=5
125 “=8

108

 

 

 

 

 

° 0
H )L
/ \ C7 Cl (:7 l \
o I
A \/ SnCl4 ~ °\/
0 H o
77 105
321-I6
c" (3W Ce
/ \ 0“ / \
O = o\/
p: Na g
o o
107 n=5
108 n=- 8 106
WOACM
On Ca Ca
no / \ o\/© 70% AcOI-I-HZO; / \ / \
N 821020 0' fl 0028:!
H 0 (1321:042qu
111 n=5
109 0:5 112 n-8
110 n-8
HZ/Pd-C
11
On On On On
I \ / --/ _ Brz/HCOOH / \ l \
Br N N Br H020 N N COZH
H - H+ H H
Br
113 0:5
115 n=5
116 n-8 114 n=8

109

refluxing acetic acid-water (70:30) for self-condensation to yield
dipyrrylmethanes (111) and (112) in 78% yield, after recrystallization from
ethanol-water. The dipyrrylmethanes (111) and (112) were hydrogenated in
THF with 10% palladium/ carbon to give the acid analogues (113) and (114)
which were directly treated respectively for one hour at room temperature
with anhydrous formic acid in the presence of an excess amount of bromine
without isolation of them because of their poor solubility in THF. After
reaction, catalyst carbon was removed by filtration and the desired
dipyrrylmethenes (115) and (116) were obtained as violet crystals in 82% yield.

The other dipyrrylmethene (123) was synthesized according to m
21, The dipyrrylmethene (123) was prepared by the condensation of two
pyrroles (121) and (122) in methanol in the presence of an excess amount of
48% hydrobromic acid. The reaction was accomplished within 30 minutes on
a steam bath.

Alanine was heated in pyridine with an excess of acetic anhydride to
give 3-acetamido-2-butanone (117) as a light yellow liq. (b.p. 110-125 0C / 3 mm)
in 88% yield, which was treated in refluxing hydrochloric acid for 8 hours to
give 3-ammonio-2-butanone chloride (118) as a white powder in 88% yield.
The ammonium salt (118) was allowed to react with diethyl oxalacetate
sodium salt in water in the presence of sodium hydroxide to yield the acid
pyrrole (119) in 37% yield, which was decarboxylated by heating in molten
mixture of NaOAc-3H20-KOAC (1:1) to give the a-free pyrrole (120) in 94%
yield. The formylpyrrole (121) was then obtained by the Vilsmeier reaction of
the or-free pyrrole (120) with DMF/POC13 in 56% yield.

As shown in Scheme 22, the porphyrin ammonium salts (132) and
(133) were synthesized as follows. The ester group of the porphyrins (124) and
(125) was hydrolyzed with potassium hydroxide in pyridine, chlorinated with

110

 

 

 

 

 

 

0
NH2 0 o k
. . HN
N014 + )LOJK pyridine : O
o
117
HC1,A
51020
O 0 I 1;
Etc 30 Etozc cm 0
I \ f NaOAc-3HZO / \ t I
H KOAC, A H020 H Ham
cr
120 119 118
DME/roq3
it
/ \
0 max 0028
7% " °
122 / \ "
OHC N 3 N / N’
H 48%I-IBr,MeOI-I,A H 13,- H‘
121
123

53113321

111

 

 

 

COzEt 002”
KOH/Py
On On On On
124: n: 5 126: n: 5
125: n=8 127: n=8
03:01
0 Cl
H l
\
HzN/\/NM92
Cn Cn Cn cn
130: n: 5 128: n= 5
131:0:8 129zn=8
"e
H l
O N +/
\/\Nl\
Cn Ctr
132: n: 5
1332 n: 3

Sgheme 22

112

oxalyl chloride, and reacted with N,N-dimethylethylenediamine to give
aminoporphyrins (130) and (131) respectively in around 80% yields which
were separately treated with an excess amount of iodomethane to give the
final cationic porphyrins (132) and (133) respectively as described before.

Another cationic porphyrinone (136) was prepared from porphyrinone
(134) as described in Scheme 23. The porphyrinone (134) was prepared by
oxidation of the porphyrin (124) with osmium tetroxide in dichloromethane
and pinacolic rearrangent with perchloric acid in 35% yield as described
before. The obtained porphyrinone (134) was treated with potassium
hydroxide in pyridine, oxalyl chloride and then N,N-
dimethylethylenediamine to give aminoporphyrinone (135) which was
further treated with an excess amount of iodomethane to give the desired
cationic porphyrinone (136) as described before.

In order to prepare the mesa-dimethyliminium chloride derivatives
(145, 146, 147, 148, 149, 150, and 151) in ficheme 24, nickel(II)
octaethylporphyrin (138) was treated with 3-DMA/POC13 for 10 hours at room
temperature to give mesa-acrolein derivative (140) in 87% yield after the
normal hydrolysis of the imine salt intermediate with saturated aqueous
sodium carbonate. The cyclization of the acrolein group onto the adjacent
pyrrole subunit B-position occured by treatment of the compound (140) in
18% sulfuric acid in trifluoroacetic acid with hydrogen sulfide for one hour at
room temperature to produce the metal-free benzochlorin (142) in 82% yield.
The compound (142) was previously prepared by Smith and Vicente125v126 by
two-step process, consisting of cyclization with concentrated sulfuric acid
followed by demetallation with trifluoroacetic acid and 1,3-propanedithiol in
4.7% overall yield, along with a 70% recovery of the nickel(II) complex (143).

The nickel(II) complex (143) was prepared from metallalation of the

113

 

 

 

002E!
(1) 0504
(2) H*
C, 05
124
0 Cl
0 Cl
05
0 cs
HgN/\/NM°2
O H
N\/\N/
\
Mel
C,
0 05
135

Cs

002 E!

KOH/Py

OOZH

H

I -
\/\N+/
\

114

3-DMA

 

 

a \ CHO
137 M=2H 14o MgNi
138 M=Ni 141 M=Cu
139 M=Cu
H ’7st
, DMF/POCIa
,w\o -
145 M=2H 142 M=2H
146 M=Ni 143 M=Ni
147 M=Cu 144 M=Cu
148 M=Zn 0,9
a
i 80¢
$03“
0
CHO ,N+\o
152 M=Ni; 2H ’ 149 M=2H
150 M=Cu
151 M=Zn

115

octaethylbenzochlorin (142) with nickel(II) chloride in 95% yield, or from
cyclization of the nickel(II) compound (140) with concentrated sulfuric acid in
47% yield. Treatment of the nickel complex of octaethylbenzochlorin (143)
with DMF/POC13 (overnight at room temperature) gave the nickel meso-
dimethyliminium chloride derivative (146) in 91% yield. Removal of the
robust central nickel(II) ion from the compound (146) was accomplished by
using concentrated sulfuric acid for 4 days at room temperature, and a 40%
yield of the metal-free iminium chloride benzochlorin (145), along with a
40% yield of the metal-free sulfonated benzochlorin (149). A better way to
prepare the metal-free iminium chloride benzochlorin (145) is the treatment
of copper(II) complex of octaethylbenzochlorin (144) with DMF/POC13, which
gave copper(II) mesa-dimethyliminium octaethylbenzochlorin (147),
followed by the treatment of copper(II) complex (147) with concentrated
sulfuric acid for 4 hours at room temperature to afford the metal-free
iminium benzochlorin (145) in 78% yield. The copper(II) complex of
octaethylbenzochlorin (144) was obtained by reflux of octaethylbenzochlorin
(142) with copper acetate in dichlormethane-methanol (3:1), for 20 minutes,
in 97.5% yield. According to our experience, in order to prepare the iminium
chloride benzochlorin (145) in better overall yield, without isolation, the
crude nickel(II) compound (140), obtained by the treatment of the nickel(II)
octaethylporphyrin (138) with 3-DMA/POC13, was first treated with hydrogen
sulfide in 18% sulfuric acid/trifluoroacetic acid for one hour at room
temperature to give directly the metal-free benzochlorin (142) which was
treated with copper acetate in refluxing dichloromethane-methanol (3:1) for
20 minutes to form the copper(II) octaethylbenzochlorin (144). The
compound (144) was treated with DMF/POC13 to produce the copper(II) meso-

dimethyliminium octaethylbenzochlorin (147) which was treated with

116

 

 

142

975%

 

 

 

 

 

 

 

 

 

95%

 

144

 

 

 

 

 

 

 

 

 

 

 

87$

 

 

 

138

a?

 

 

 

143

 

 

 

91%

 

 

149

 

76%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

117

concentrated sulfuric acid for 4 hours at room temperature to afford the
metal-free iminium benzochlorin (145) in 48% overall yield from the nickel
octaethylporphyrin (138) (in 4 steps). The sulfonated derivative (149) was
prepared by the treatment of the nickel(II) compound (146) with concentrated
sulfuric acid for 4 days as mentioned before. An outline of overall reaction
for effective preparation of benzochlorin derivatives and iminium

derivatives was summarized in Scheme 25.

III. RESULTS AND DISCUSSION

Broadly cationic porphyrin derivatives, prepared and characterized in
this study, can structually fall into two categories: cationic groups linked with
the B-position of pyrrole and with the mesa-position of
octaethylbenzochlorin. In the former category, the porphyrins (87, 97, 124,
and 125) containing ester group were easily transformed into the N-[2-
(dimethylamino)ethyl]carbamido derivatives (90, 100, 130, and 131) which
were purified and analyzed by UV-vis spectrophotometer, 1H NMR
spectrometer, and mass spectrometer. All the amino compounds (90, 100, 130,
and 131) were purified before being treated with iodomethane to afford the
desired cationic compounds (91, 101, 132, and 133). All their spectral results
are shown in Table 5. The cationic compounds have the same absorbance
spectra as their amino compounds which are also similar to that of the parent
porphyrins. Enhancing long-wavelength absorption was achieved by
introduction of oxo group on porphyrin ring. The ketochlorins (104, 136)
were easily prepared by oxidation with osmium tetroxide and by acid-

catalyzed pinacolic rearrangement as mentioned before. The oxidation of the

118

Table 5 UV-vis absorption spectral data of cationic porphyrin derivatives
containing trimethylammonium group ( 91, 101, 104, 132, 133 and 136) and
their precursors (87, 90. 97, 100, 102, 103, 124, 125, 130, 131, 134 and 135).

 

 

 

 

 

 

 

 

 

 

Compound Soret IV III II I
87 397 497 531 565 618
90 397 497 531 565 618
91 396 497 531 565 618
97 406 506 545 l 573 628
100 408 506 542 574 628
101 408 506 542 574 628
102 319 412 537 568 643
103 404 417 541 573 647
104 404 417 542 573 648

 

124,125 406 509 547 573 630

 

130, 131 403 504 541 568 622
132, 133 403 505 542 569 623
134 412 524 516 578 634

 

 

 

135 412 524 516 578 634

 

 

 

 

 

 

 

 

136 413 525 561 579 635

 

119

porphyrin (97, 124) mainly effected dihydroxylation at the diagonal pyrrole
double bond of the pyrrole containing ester group as would be expected by
electronic effects. The cationic ketochlorins (104, 136) showed 12~20 nm red
shift and an increase of intensity in the visible region as compared with the
corresponding cationic porphyrins (101, 132) as shown in Table 5.

In the first category monocationic porphyrin (MCP) derivatives, IZ-{N-
[2-(trimethylammonio)ethyl]carbamido}-3,7-diethyl-2,8,13,17,18-pentamethyl
porphyrin iodide (91) was fully examined by biologic study. It has a typical
porphyrin absorbance spectrum, with maxima at 396 >> 497 > 531 > 565 > 618
nm. MCP (91) has similar extinction coefficients to protoporphyrin IX (PP) at
these wavelengths, although the spectrum of MCP (91) is slightly red-shifted.
The octanolzwater partition ratio (P) for MCP (91) was 6, indicating a much
less hydrophobic structure than that of PP, P=180.

In MCP (91) vs. PP accumulation in vitro, after a 30 minutes incubation
at 37 0C, the distribution ratios of MCP and PP were 15 and 130, respectively,
indicating preferential uptake of the former sensitizer. In vivo PDT studies
and drug biodistribution in human plasma have been carried out.123

As mentioned before, our discovery that protonated Schiff bases
(imines) of "chlorin-type" compound show an unusual red shift of the
absorption maxima in the visible region50r51 prompted us to investigate the
synthesis of another type of cationic PDT photosensitizers by introduction of
dimethyliminium group on mesa position of octaethylbenzochlorin. The
nickel(II) octaethylbenzochlorin (NiOEBC; 143) was easily prepared by
treatment of the nickel(II) formylethenylporphyrin (140), obtained by
treatment of the nickel(II) octaethylporphyrin (NiOEP; 138) with 3-
DMA/ POC13, with concentrated sulfuric acid, which was developed by

120

Smith.125 However the metal-free octaethylbenzochlorin (OEBC; 142) was
obtained in poor yield (~10%) by treatment of NiOEBC (143) with
trifluoroacetic acid and 1,3-propanedithiol. In our study, OEBC was easily
prepared through one-step reaction: when the nickel(II)
formylethenylporphyrin (140) was treated with hydrogen sulfide in 18%
sulfuric acid/trifluoroacetic acid, both cyclization and demetallation took
place to afford directly the metal-free OEBC in 82% yield. Evidence
supporting the formulation of OEBC (142) was given both by mass
spectrometry (molecular ion at m/e=572) and by 1H NMR spectrosc0py. In
the latter spectrum, the resonances of two ethyl groups were upfield of the
remaining ethyl groups as expected for moieties attached to the sp3 hybridized
carbon of a reduced pyrrole ring. The three resonances attributable to the
protons of the newly formed aromatic ring (doublets at 8:802; 9.53; triplet at
8.10 ppm). The three mesa protons absorb at 8:801, 8.56, and 9.22 ppm.

The Vilsmeier formylation reaction has been used as an efficient
method for introduction of substituents into the mesa positions of numerous
copper(II) and nickel(II) porphyrins and chlorins. In a typical experiment, the
iminium salt that is formed after the addition of the Vilsmeier complex, is an
unstable intermediate and is therefore hydrolyzed to the formyl group, using
sodium acetate aqueous solution, immediately after is formed, and without
further characterization.

Copper ion was inserted into OEBC (142) before it was converted into
copper(II) dimethyliminium octaethylbenzochlorin (CuImBC; 147) in 75%
yield by the Vilsmeier reaction (DMF/POC13). Surprisingly CuImBC is so
stable that the iminium group survives in conc. H2804 over extended time.
CuImBC was converted into the free base dimethyliminium

octaethylbenzochlorin (ImBC; 145), after 5 hours reaction without yielding

121

any side products. The structure of ImBC was supported both by mass
spectrometry (molecular ion at m/e=628.4) and by 1H NMR spectroscopy. In
1H NMR spectrum, the resonances of two ethyl groups were upfield of the
remaining ethyl groups as those of OEBC. The three resonances attributable
to the protons of the formed aromatic ring absorb at 5:7.81, 8.78 ppm (two
doublets) and 7.81 ppm (triplet). The newly formed dimethyliminium group
was proven both by the two resonances attributable to the methyl protons
(singlets at 8:277; 4.32 ppm) and by the resonance of the methine proton
(singlet at 6:10.31 ppm).

ImBC (145) is unique among iminium salts in that its iminium group
is extremely resistant to hydrolysis. To examine this stability issue in
perspective several related compounds were compared. The imine or
iminium derivatives (1 and J) hydrolyzed easily in wet organic solvents with
half-live < 3 minutes at room temperature. The chlorin derivatives (K) and
(L) also hydrolyzed easily (half-life < 10 minutes). In contrast, nickel(II)
complex of ImBC, NiImBC (146), required at least 12 hours treating with

aqueous sodium acetate solution before it changed to its formyl derivative.

~o
IN-Bu OH ..

I

’ NWO;

L X=CH2

Sul

COI

12

Subsequent hydrolysis of CuImBC to Cu(II) formylbenzochlorin was
completed in 15 hours. The unusual resistant to hydrolysis is what makes it
possible to carry out demetallation of the copper in CuImBC as well as re-
metallation of the resultant free-base ImBC to afford other metal derivatives
for PDT studies.

The exceptional stability of the iminium group in ImBC is interesting
and may arise from structural and/ or electronic effects. Structurally the
mesa-substituted dimethyliminium group is adjacent to the geminal diethyl
groups on the neighboring pyrrole which may provide steric shielding to
hinder hydrolysis of the iminium group. However, comparisons with a
recently synthesized ketochlorin derivatives (K and L) suggest that shielding,
if any, by the geminal ethyl groups may be insufficient to impart such
unusual stability because they (K and L) are still very labile toward hydrolysis.

Electronically, the benzochlorin ring may alter the rate of nucleophilic
attack on the conjugated iminium carbon leading to hydrolysis. Currently
there is little known about the electronic properties of these compounds. The
iminium salt seemed stable enough to withstand electronic attack because
sulfonated ImBC (SImBC; 149) has been made by trteatment of NiImBC or
CuImBC with cone. H2504 for 4 days. This SImBC also possesses good
stability and can be converted quantitatively into its Ni—, Cu- and Zn-complex.
Evidence supporting the structure of SImBC was given both by mass
spectrometry (molecular ion at m/e=708) and by 1H NMR spectroscopy. In
the latter spectrum, the resonances of two ethyl groups were upfield of the
remaining ethyl groups as those of ImBC (145). The resonances of three
protons of the aromatic ring of ImBC (doublets at 8:781; 8.78; triplet at 7.81
ppm) were replaced by two singlets (at 5:825; 9.33 ppm). The absence of the

triplet resonance and the change in chemical shifts of the remaining singlets

123

are all consistent with sulfonation alpha to both protons. The resonances of
the methyl protons (singlets at 5:271; 3.79 ppm) as well as the methine
proton (singlet at 8:937 ppm) of the dimethyliminium group still exist.

Both ImBC and SImBC exhibit a strong absorbance in the vicinity of 800
run, while insertion of a nickel, copper or zinc ion into ImBC (or SImBC)
results in a blue-shift of the absorption of band I approximately 25, 45 and 60
nm respectively (Figure 9 and Figure 10).

Initial studies involved comparison, of Ni(II) and Cu(II) benzochlorin
iminium salts. Both are paramagnetic metals, but the Ni atom has more low-
lying energy state5125'126 which could result in inhibition of photoprocesses.
Biologic studies, involving a clonogenic assay and FANFT tumor, indicated
that NiImBC formulated in Cremophor EL (CRM) was inactive in vitra at
levels as high as 1.4 pM.127 It was also found no effect of a 7 mg/kg (10
moles / kg) dose of NiImBC against the FANFI' tumor in viva. To assess the
need for iminium group, we prepared an analog of NiImBC with an aldehyde
group replacing the iminium group. This product had no phototoxic effect
on the FANFT cells in culture or in the rat.128 The iminium group therefore
represents an essential element in the production of photodamage.

Initial photophysical experiments indicate that the triplet state lifetime
of CuImBC extremely short ( < 20 nsec) and that singlet oxygen is not
produced during photoactivation.‘53v129 Hence, CuImBC has no tendency to
initiate type II photodynamic activity. It was found that photoactivation of
CuImBC formulated in CRM resulted in decreased blood flow. It have been
demonstrated that singlet oxygen generated by photosensitizers disrupted
tumor blood flow when measured immediately after irradiation.69 Further
studies have been proposed to examine the mechanism of vascular

shutdown, specially endothelial cell integrity. Using a suspension of

124

 

 

 

 

 

sane: REF:
+2.000 1%- . . - .
E O
0
I
‘P ‘ :‘0‘ 4r
:: 0;.
0. 0 /\ 3 :
(ct/310a,, ; t E: .‘
‘6 zir.‘
v :OI.\|
,‘ll', 1
”73' “\\“ 1r
3 \
fl? \\
’ J" 0 ‘\
0‘.:’I o. .o ’ \ \.\\
Q . 0... \‘~.\ [
30.000 . t t t : 3 - NH
' 300.0 100.0(NH/DIU.) 900.0

 

[7900.0NH 0.0003

Figure 9. UV-vis absorption spectra of ImBC (145; -—-), NiImBC (146; - - -).

 

 

 

 

 

 

 

CuImBC (147;- . ..) and 2111ch (14s; ------ ) in CH2C12-
SQHP= REF:
+2080“ :. ; : 1" '7 ;
[‘l
i 4)
I l .. r.
0.500 i ./i -‘ z
( RIDIU. ) . ,' 5 V

.- I ' 1‘ 5 f. \'
' I 1 : ’ \.

I ' . . I ‘

s. ‘ I .

,' l

l 1 ‘-. i ..

t- .r" '

0. [I 2 l

.\;;d fl. .‘1 \-

+0.000 1i i z: 5. . 154. NH
300.0 100.0(NH/DIU.) 900.0
[ 900.01"! 0.0003]
Figure 10. UV-vis absorption spectra of SImBC (149; -), CuSImBC (150; ------ )

and 21151ch (151; — . —) in CHzClz.

125

erythrocyte ghosts, it was found that addition of either superoxide dismutase

(a superoxide quencher) or catalase (a H202 quencher) resulted in a substantial

inhibition of erythrocyte ghost lipid peroxidation produced by CuImBC (in

DMSO) and exposed to broad band red light (590~850 nm) from a xenon are

light source. In contrast, neither enzyme was effective in a system containing

type II photosensitizer. These results indicate the involvement of oxygen

Table 6. In vitra phototoxicity of iminium salts (145, 146, 147 and 148)

 

 

 

 

 

 

 

 

 

 

 

 

Light dosea’) Absorbance“)
Drug DR(a) ( I/ cmz) 2. (nm) OD ICso (d) Efficacy“)
145 2.8 0.53 753 0.21 84 28 ’
148 2.6 1.92 723 0.47 104 6.3
147 11 3.84 733 0.38 330 1.0
146 13 >20 735 0.5 N/ A 0

 

 

 

a) Distribution ratio of intracellular to extracellular sensitizer

concentration at steady-state conditions.

b) For 50% cell kill with a 30 11M extracellular concentration.

c) Absorbance (optima and OD) of a 10 W sensitizer solution in
ethanol.
d) Intracellular sensitizer concentration required decrease in cell

viability
e) Based on light dose and intracellular dye level.

to 50%.

'L1210 cells were incubated with a 30 MM sensitizer concentration formulated in
Creniophor EL for 30 min at 37 0C, then irradiated at 610-800 nm with a sufficient light
dose to lethally photodamage 50% of the cell population. The resulting intracellular

sensitizer levels are shown, along with the required light dose. Efficacy is estimated

in terms of cells killed/ light dose [IC level]. For the purpose of this comparison, the
efficacy of CuBI is defined as 1.

126

radicals other than singlet oxygen in the phototoxicity of CuImBC. Since both
ZnImBC and ImBC fluoresce and possess a significantly longer triplet lifetime
when compared to CuImBC, it was predicted that both these iminium salts
are singlet oxygen generators.

ImBC and ZnImBC were carried out with L1210 cells to assess the
efficacy of photodamage in vitra. The comparisons shown in Table 6 indicate
that the metal free iminium salt is the most potent sensitizer, while Cu
analogue is much less effective; the Ni analogue shows no activity. These
results may reflect the capacity of ZnImBC or ImBC to catalyze both type I and
type II reactions. It should be noted that these results reflect only efficacy in
cell culture, and that the results in an experimental animal tumor system

may be quite different.

IV. EXPERIMENTAL

12— N- - Dime h lamino th 1 arbamid -3 7 ieth l- 13 17 1 - enta-
2W

Ethyl 3,7-diethyl-2,8,13,17,18~pentamethylporphyrin-12-propionate- (87)
(102 mg, 0.19 mmol) was dissolved in trifluoroacetic acid (25 mL) and mixed
with concentrated hydrochloric acid (2-3 mL). This solution was heated on a
steam bath for 6 hours or until hydrolysis was completed which was
monitored by TLC. After hydrolysis, the solvent was evaporated and dried
under vacuum to yield the acid porphyrin (88). Without purification, this
acid porphyrin was suspended in dry dichloromethane (50 mL) and then
oxalyl chloride (0.17 mL, 1.9 mmol) was slowly added in an ice bath. After the

127

chlorination by stirring for one hour at room temperature, the solvent was
removed under vacuum to give the carbonyl chloride porphyrin (89).
Without isolation, this product was directly dissoved in dry dichloromethane
(50 mL) and then N,N-dimethylethylenediamine (0.03 mL, 0.27 mmol) was
slowly added in an ice bath. After stirring for one hour at room temperature,
the solvent was evaporated to dryness under high vacuum to remove excess
N,N-dimethylethylenediamine. The resulting residue was chromatographed
on silica gel with 15% methanol in dichloromethane. The desired compound
was collected to give the title compound (88 mg, 80%): 1H NMR (CDC13) 5
-3.99 (2H, 5, NH), 1.59 (6H, s, N132), 1.79 (2H, t, -NHCH2QI;N), 1.87 1.88 (3H
each, t, peripheral -CH2C_H;), 2.96 (2H, t, CHzg‘igCO), 3.07 (2H, q,
-NH§LI__2_CH2N), 3.43, 3.44, 3.47, 3.54, 3.61 (3H each, s, 2, 8, 13, 17, 18-CH3), 4.06,
4.07 (2H each, q, peripheral figCI—Is), 4.29 (2H, t, @CIQCO) 5.65 (1H, brs,
peripheral NH), 9.82, 9.89, 9.98, 10.05 (1H each, s, meso H); UV-vis (in 10%
CHgOH/CHzCh) km (8..) 618 nm (4, 800), 565 (6, 600), 531 (9, 900) 497 (13, 700),
397 (153, 600); M5 for C36H46N60, found m/ e 578.3 (M"').

12-lN-l 2-( Trimethylammgnio )ethyl Icarbamidol-3 ,7-diethyl-2,§,13,I 7,18-
am h l o h ' i id
12-{N-[2-(Dimethylamino)ethyl]carbamido}-3,7-diethyl-2,8,13,17,18-

pentamethylporphyrin (90) (40.5 mg, 0.07 mmol) was dissolved in
dichloromethane (35 mL) containing 10% methanol and then iodomethane
(0.044 mL, 0.7 mmol) was added. The reaction mixture was stirred for 5 hours
at room temperature and the solvent was evaporated to dryness under
vacuum to give the title compound in almost quantitative yield: UV-vis (in
10% CH3OH/CH2C12) 1m (EM) 618 nm (2, 300), 565 (4, 650), 531 (5, 850), 497 (7,
470), 396 (88, 350); M5 for C37H49N60I, found m/ e 593.7 (M+).

128

 

WM
4-(2-Chloroethyl)-3,5-dimethylpyrrole-Z-carboxylic acid (75) (6.05 g, 30

mmol) and 3-(ethoxycarbony1)-2-formyl-4,5-dimethylpyrrole (92) (5.85 g, 30
mmol) were dissolved in methanol (80 mL). 48% hydrobromic acid (8 mL)
was added dropwise to the stirred solution and the reaction mixture was
heated on a steam bath for 10 minutes. Some red purple crystals formed
immediately. After standing over night at room temperature, the
precipitated solid was collected by filtration, washed with methanol
containing small amount of hydrobromic acid, and finally rinsed with a small
amount of ether to give the title compound as a red-purple powder (9.27 g,
92% yield): m.p. 201-203 °C; 1H NMR(CDC13) 8 1.44 (3H, t, 00-12%), 2.27,
2.37, 2.70, 279 (3H each, s, 3', 4, 5, 5'-Me), 2.94 (2H, t, flflgCHzCl), 3.60 (2H, t,
-CH2Q_I_~_I;C1), 4.41 (2H, q, -OC_HgCH3), 8.44 (1H, s, methine), 13.32, 13.50 (1H
each, br 5, NH); MS for C17H24N202BrCl, found m/ e 335.3 (Mi).

3,3'-Diethyl-4,4'-dimethyl-2,Z'dipmlmethang (25)
5,5'-Bis(ethoxycarbonyl)-3,3'-diethyl-4,4'-dimethyl-2,2'-dipyrrylmethane
(94) (29.96 g, 80 mmol) was dissolved in hot ethanol (100 mL) and 40%
aqueous potassium hydroxide (25 mL) was added. The hydrolysis was
accomplished by refluxing for 2 hours and then the solvent was evaporated to
one third by heating without condenser. The condensed reaction mixture
was diluted with water (40 mL) containing a few drops of hydrazine and
refluxed 24 hours. At the end of this period, a layer of brown oil was
separated which was solidified at room temperature. The solidified material

was collected by filtration and washed with water to give the title compound

129

as a dark-brown shinny solid (18.09 g, >98%): m.p. 51-53 °C ; 1H NMR (CDC13)
8 1.12 (6H, t, 'CHZQHQ), 2.03 (6H, s, 4, 4'-Me), 2.47 (4H, q, .-§H_2CH3), 3.79 (2H, s,
methylene), 6.35 (2H, m, 5, 5'-H), 7.26 (2H, br 5, NH); M5 for

 

3,3'-Diethyl-4,4'-dimethyl-2,2'dipyrrylmethane (95) (9.21 g, 40 mL) was
added in small portions into a mixture of anhydrous formic acid (60 mL) and
bromine (2.08 mL, 40 mmol) with stirring at room temperature. The reaction
mixture was stirred for an additional 30 minutes during which some solids
precipitated. Most of formic acid was evaporated under reduced pressure to
give solid product which was dried in vacuo and triturated in cydohexane
containing small amount of cyclohexene to remove excess bromine. The
solid product was collected by filtration and dried in air to give the title
compound (18.12 g, 97%): M5 for C15H19N2Br3, found m/ e 386 (M+).

Eth l - 2-chloroeth l -1 17-dieth l-2 7 12 18-tetrameth l r h rin- -
carboxylate (92)
4'-(2-Chloroethyl)-3-(ethoxycarbonyl)-3',4,5,5'-tetramethyl-2,2'-dipyrryl—
methenium bromide. (93) (6.72 g, 20 mmol) and 5,5'-dibromo-3,3‘-diethyl-4,4'-
dimethyl-2,2'-dipyrrylmethenium bromide (96) (9.34 g, 20 mmol) were
dissolved in anhydrous formic acid (70 mL) and treated with bromine (1.04
mL, 20 mmol). The reaction mixture was heated to reflux in an oil bath for 2
hours. The solvent was then allowed to boil off over 4 hours with a stream of
air (until dryness). The residue was redissolved in ethanol containing a few
drops of concentrated sulfuric acid and triethyl orthoformate (5 mL). After
standing overnight , protected from moisture, the reaction mixture was

diluted with dichloromethane (100 mL) and then meutralized with saturated

130

aqueous sodium acetate (50 mL). The organic layer was separated, washed
once again with saturated sodium acetate (30 mL) and then twice with water
(50 mL). After evaporation of the solvent, the residue was chromatographed
on a silica gel column with 0.5% of methanol in dichloromethane as eluent.
The fractions containing the expected porphyrin were combined and
recrystallized from dichloromethane and methanol to give the title
compound (957 mg, 8.6%): m.p. 245-247 °C; 1H NMR (CDC13) 8 -3.70 (2H, br 5,
NH), 1.92 (9H, overlapping t, CH2CH3, -OCHzCH3), 3.52, 3.64, 3.66, 3.94 (14H, 5,
Me), 3.98, 4.08 (4H, q, CH2CH3), 4.28, 4.50 (2H each, t, CH2CH2C1), 4.90 (2H, q,
~OCH2CH3), 9.85, 9.95, 10.15, 11.10 (1H each, s, meso H); UV-vis (in CH2C12)
law (8”) 628 (3,300), 573 (7,300), 545 (10,400), 506 (12,900), 406 (172,000); M5 for
C33H37N402Cl, found m/ e 556.4 (M+).

- N- 2- Dimeth lamino eth l carbamido -1 17-dieth l-2 7 12 1 t am th 1-
MW
Ethyl 8-(2-chloroethyl)-13,17-diethyl-2,7,12,18-tetramethylporphyrin-3-
carboxylate (97) (55.7 mg, 0.1 mmol) was dissolved in pyridine (20 mL) with
heating and aqueous potassium hydroxide (5%, 4 mL) was added. The
reaction mixture was heated under reflux for 1 hour or until the hydrolysis
was completed which was monitored by TLC. After hydrolysis, the reaction .
mixture was diluted with water (100 mL) and neutralized with acetic acid
until the acid product precipitated and then filtered through a bed of celite.
The product was extracted from the celite with formic acid and the filtrate was
evaporated to dryness under vacuum to give the acid vinylporphyrin (98).
Without purification, this acid product was suspended in dry
dichloromethane (30 mL) and then oxalyl chloride (0.1 mL, 1.1 mmol) was
slowly added in an ice bath. After the chlorination by stirring for 1 hour at

131

room temperature, the solvent was removed under vacuum to give the
carbonyl chloride porphyrin (99). Without isolation, this product was also
dissoved in dry dichloromethane (30 mL) and then N,N-
dimethylethylenediamine (0.02 mL, 0.18 mmol) was slowly added in an ice
bath. After stirring for 1 hour at room temperature, the solvent was
evaporated to dryness under high vacuum to remove excess N,N-
dimethylethylenediamine. The resulting residue was chromatographed over
silica gel with 15% methanol in dichloromethane. The desired compound
was collected to give the title compound (43.9 mg, 78%): 1H NMR (CDC13) 5
-4.28 (2H, br s, NH),1.74, 1.76 (3H each, t, CHLQ-Ié), 2.49 (6H, s, NMgz), 2.94
(2H, t, CONHCHZQIjgN), 3.35, 3.41, 3.66, 3.68 (3H each, 5, ring Me), 3.90 (4H, q,
LHgCl-ng), 4.05 (2H, q, CONHCiigCI-IZN), 6.15, 6.35 (1H each, dd, 01%), 7.64
(1H, br s, CONE), 8.17 (1H, dd, £11m), 9.65, 9.70, 9.87, 10.40 (1H each, s,
meso H); UV-vis (in 10% CH3OH/CH2C12) lmax (EM) 628 nm (3,000), 574
(6,900), 542 (10,000), 506 (12,500), 408 (166,000); M5 for C35H42N50, found m/ e
562.3 (M+).

3;] N-I 2-(Trimethy1ammonio )ethyl |carbamidol-13,1 7-diethyl-2,7,12,18—
tggamethyl-S-vinylpogphm’n iodide (101)
3-(N-[2-(Dimethylamino)ethyl]carbamido}-13,17-diethyl-2,7,12,18-

tetramethyl-8-viny1porphyrin (100) (39.4 mg, 0.07 mmol) was treated with
iodomethane (0.044 mL, 0.7 mmol) following the method described for the
ammonium compound (91) to give the title compound (48.3 mg, 98%): UV-
vis (in 10% CH3OH/CH2C12) lmax (EM) 628 nm (3,000), 574 (6,900), 542 (10,000),
506 (12,500), 408 (166,000); M5 for C36H45N601, found m/ e 577.6 (M+).

132

Eth l - 2- hloroeth 1-12 17-dieth 1-2712 18-tetrameth 1-1 - o h in ne- -
carboxylate (102)

Osmium tetroxide (88 mg, 1.5 mmol) and pyridine (0.05 mL) were
added to ethyl 8-(2-chloroethyl)-13,17-diethyl-2,7,12,1B-tetramethylporphyrin-
3-carboxylate (97) (195 mg, 0.35 mmol) was dissolved in dichloromethane (45
mL). After the reaction mixture was stirred for 24 hours at room temperature
under nitrogen in the dark for 24 hours, it was quenched by adding methanol
(10 mL), then bubbled with hydrogen sulfide through the reaction solution
for 30 minutes to decompose the osmate adduct and allowed to stand for 2
hours. The precipitated black osmium sulfide was removed by filtration
through a bed of Celite and the filtrate was evaporated. The resulting residue
was dissolved in dichloromethane (50 mL) and perchloric acid (70%, 0.8 mL)
was added and then stirred for 30 minutes at room temperature. The reaction
mixture was diluted with dichloromethane (50 mL) and the organic layer was
washed twice with saturated aqueous sodium acetate (50 mL) and twice with
water (50 mL). The organic layer was dried over anhydrous sodium sulfate
and the solvent was removed under vacuum and the residue was
chromatographed on silica gel with dichloromethane as eluent to give the
title compound (64 mg, 32%): 1H NMR (CDC13) 8 -3.66 (2H, br 5, NH), 1.74 (3H,
t, 12—CHgfi3), 1.92, 1.94 (3H each, t, 17-CI-Iflig, 3-OCH7_C_I-_1§), 2.07 (3H, s, 12-
Me), 2.98 (2H, q, IZ—QH;_CH3), 3.52, 3.64, 3.66 (3H each, 5, ring Me), 4.08 (2H, q,
17%CH3), 4.28 (2H, t, —CH2_C_Ii;Cl), 4.50 (2H, t, -QIi;CH2Cl), 4.90 (211, q,
-OC_I;I;_CH3), 9.12, 9.67, 9.75, 10.35 (1H each, s, meso H); UV-vis (in CH2C12)
km (8“) 643 nm (15,600), 568 (18,000), 537 (8,400) 412 (182,000), 319 (17,100); M5
for C33H37N403Cl, found m/ e 572.5 (M+).

133

klN-I2-(Dimethy1amingzethy1IcarbamidQl-l 2,1 7-diethyl-2,7,1 2,1 8-tggamgthy1-
8—viny1-13-porphyrinone (103)

' Ethyl 8-(2-chloroethy1)-12,17-diethyl-2,7,12,18-tetramethyl-13-
porphyrinone-B-carboxylate (102) (57.3 mg, 0.1 mmol) was treated with excess
potassium hydroxide, with oxalyl chloride (0.1 mL, 1.1 mmol) and with N,N-
dimethylethylenediamine (0.02 mL, 0.18 mmol) following the method
described for the porphyrin amide (100) to afford the title compound (43.7 mg,
75.6%): 1H NMR (CDC13) 8 -3.72 (2H, br 5, NH), 1.76, 1.95 (3H each, t, CHflé),
209 (3H, s, 12-Me), 2.96 (2H, t, NHCHZC_H;N), 3.02 (2H, q, 12-§_I_-I_;CH3), 3.98
(2H, q, NHC_H;CH2N), 4.06 (2H, t, 17-Q_Ii;CH3), 6.18, 6.40 (1H each, dd,
-CH=Q12_), 7.77 (1H, br s, CO_N_H_), 8.27 (1H, dd, —_C_I-_I_=CHz), 9.14, 9.68, 9.78, 10.42
(1H each, s, meso H); UV-vis (in 10% CHgOH/ CH2C12) lmax (EM) 647 nm
(14,500), 573 (17,800), 541 (8,300), 417 (17,900), 404 (16,800); MS for C35H42N602,
found m/ e 578.2 (Mt).

N- 2- Trimeth lammoni th 1 ar amid -1217— i th 1-27121
tgtgamethyl-8-vinyl-13—pogphm'none iodide (104)
3-(N-[2-(Dimethylamino)ethyl]carbamidol-l2,17-diethyl-2,7,12,18-

tetramethyl-8-viny1-13-porphyrinone (103) (34.7 mg, 0.06 mmol) was treated
with iodomethane (0.38 mL, 0.6 mmol) following the method described for
the ammonium compound (91) to give the title compound (41.7 mg, 96.5%):
UV-vis (in 10% CH30H/CI-12Clz) 1mm.) 648 (14,500), 573 (17,800), 542 (8,300),
417 (17,900), 404 (16,800); M5 for C36H45N5021, found m/ e 593.5 (Mt).

Eth l imeth l-4»octano 1 ole-2-carbox late
Ethyl 3,5-dimethylpyrrole-Z-carboxylate (77) (83.5 g, 0.5 mol) was
dissolved in dry dichloromethane (400 mL) with heating. The solution was

134

cooled to 10 °C in an ice bath and octanoyl chloride (94 mL, 0.55 mol) was
added. To this solution, tin(IV) chloride (82 mL, 0.7 mol) was slowly added
through a pressure—equalized dropping funnel (temperature < 20 0C). The
reaction is exothermic only during the period when the first mole equivalent
of tin(IV) chloride was added. The reaction mixture was stirred for another 2
hours in the ice bath after the addition and then poured into ice/ water (1 L).
The organic phase was separated, washed twice with aqueous sodium
carbonate, then with water, and dried over anhydrous sodium sulfate. The
solvent was evaporated under vacuum to yield a white mass of octanoyl
pyrrole (143 g, 98%). The product was essentially pure and no further
purification was needed.

For the title compound: 1H NMR (CDC13) 8 0.85 (3H, t, octanoyl Me),
1.26 (8H, m, CH2), 1.42 (3H, t, OCHZCL-Ig), 1.65 (2H, m, CH2), 2.18, 2.29 (3H each,
s, 3,5-Me), 2.83 (2H, t, 4—COC_§_;), 4.27 (2H, q, OC_I-_-I;CHg), 8.96 (1H, br 5, NH); MS
for C17H27N03, found m/ e 293.3 (Mt).

Eth l -dimeth 140 1 ol 2-carbox late

Sodium borohydride (7.6 g, 0.2 mol) was added to the essentially pure
ethyl 3,5—dimethyL4-octanoylpyrrole-Z-carboxylate (105) (29.3 g, 0.1 mol)
dissolved in dry tetrahydrofuran (100 mL). The reaction mixture was cooled
to 10 0C with stirring in an ice bath and boron trifluoride etherate (37 mL, 0.3
mol) was slowly added so that the reaction temperature was maintained
below 20 °C. After the addition of boron trifluoride etherate, the mixture was
stirred for an additional one hour in the ice bath and then poured into a
mixture of ice (200 mL), hydrochloric acid (IN, 50 mL) and dichlormethane
(200 mL). The organic phase was separated and washed with hydrochloric
acid (0.5N, 200 mL). To the neutralized organic phase, methanol (50 mL) was

135

added and the solvent was evaporated to dryness. The resulting white
product was crystallized from methanol-water (85:15) to yield the title
compound (26.2 g, 94%): m.p. 74-77 °C; 1H NMR (CDC13) 8 0.84 (3H, t, octyl
Me), 1.25 (10H, m, CH2), 1.36 (2H, m, CH2), 1.40 (3H, t, OCHzCfig), 2.15, 2.24
(3H each, s, 3,5—Me), 2.32 (2H, t, 4-CHz), 4.25 (2H, q, -og;1_I;CH3,, 8.60 (1H, br 5,
NH); M5 for C17H29N02, found m/ e 279.4 (M+).

l - 'meth l l 1 2 ar la

After benzyl alcohol (150 mL) was heated up to 180 °C to remove
moisture, ethyl 3,5-dimethy1-4-octylpyrrole-2-carboxylate (106) (55.8 g, 0.2 mol)
was added. The reaction mixture was heated up to boiling for 10 minutes to
drive off water. To this hot homogeneous solution, a fresh saturated solution
of sodium in dry benzyl alcohol (10 mL) was cautiously added in small (1 mL)
portions under nitrogen until the evolution of ethanol ceased. Further
portions were added every several minutes until the exchange was completed
when the boiling point had again risen above 200 °C. Heating was continued
to reflux for 10 minutes after the effervescense subsided. The hot reaction
mixture was poured cautiously into a stirred solution of acetic acid (20 mL) in
methanol (400 mL), and water was then added until crystallization was
completed. The light pinkish solid was collected by filtration, washed with
50% aqueous methanol and dried to give the title compound (58 g, 85%).

For analysis a sample was recrystallized from tetrahydrofuran and
methanol: m.p. 78-81 °C; 1H NMR (CDC13) 8 0.86 (3H, t, octyl Me), 1.25 (10H,
m, CH2), 1.38 (2H, m, CH2), 216, 226 (3H each, s, 3,5-Me), 232 (2H, t, 4-CH2),
5.27 (2H, s, OQEQC6H5), 7.35 (5H, m, phenyl protons), 8.61 (1H, br 5, NH); M5
for C22H31N02, found m/ e 341.3 (Mi').

136

Bml iacgtoxmethyl-imethyl-4-pentylpmgle—2-carboxylate (102)
Lead tetraacetate (48.7 g, 0.11 mol) was added to a solution of benzy13,5-

dimethyl-4-pentylpyrrole-Z-carboxylate (107) (31.3 g, 0.1 mol) in glacial acetic
acid (150 mL) with stirring at room temperature. The reacton was
accomplished by heating on a steam bath for one hour, when the color of the
reaction mixture was changed from yellow-brown to dark-brown, and the
reaction mixture was poured into a large amount of water ( > 1 L). The
precipitated solid was separated by filtration, rinsed with water and
crystallized from aqueous acetone to give the title compound as ivory-white
needles (35.1 g, 95%): m.p. 83-86 °C; 1H NMR (CDC13) 8 0.92 (3H, t, pentyl
Me), 1.28 (10H, m, CH2), 1.43 (2H, m, CH2), 2.04, 2.27 (3H each, s, 3,5-Me), 2.42
(2H, t, 4-CH2), 5.00 (2H, s, S—grizOCO), 5.30 (2H, s, @ZCJ‘Is), 7.38 (5H, m,
phenyl protons), 9.16 (1H, br 5, NH); MS for C21H27NO4, found m/ e 357.4
(M+).

Be lae ehl—-mhl l 12-ar late

Benzyl 3,5-dimethyl4octylpyrrole—2-carboxylate (108) (34.1 g, 0.1 mol)
was treated with lead tetraacetate (48.7 g, 0.11 mol) following the method
described for the acetoxymethyl pyrrole (109) to give the title compound (38.2
g, 96%): m.p. 80-85 °C; 1H NMR (CDCL3) 8 0.87 (3H, t, octyl Me), 1.27 (10H, m,
CH2), 1.42 (2H, m, C112), 204, 2.27 (3H each, s, 3.5—Me), 241 (2H, t, 4-CHz), 5.00
(2H, s, 5—gl-IgOCO), 5.30 (2H, s, OgigcsHs), 7.37 (5H, m, phenyl protons), 9.15
(1H, br 5, NH); MS for C24H33NO4, found m/ e 399.2 (M+).

 

Benzyl 5-acetoxymethyl-3-methyl-4-pentylpyrrole-Z-carboxylate (109)
(37.1 g, 0.1 mol) was dissolved in 70% aqueous acetic acid. (200 mL) and heated
under reflux for one hour. After reaction was accomplished, the hot reaction
mixture was poured into a large amount of water and allowed to cool down

slowly to precipitate solid product. The precipitated solid was collected by

filtration, washed with water and crystallized from ethanol to give the title
compound as ivory-white needles (47.5 g, 78%): m.p. 98—101 °C; 1H NMR
(CDC13) 8 0.88 (6H, t, pentyl Me), 1.28 (8H, m, CH2), 1.38 (4H, m, CH2), 226 (6H,
s, 4,4'-Me), 2.34 (4H, t, 3,3'-CH2), 3.79 (2H, t, 2,2'-methylene), 5.21 (4H, s,
-O§flg_C6H5), 7.30 (10H, m, phenyl protons), 9.05 (2H, br 5, NH); MS for
C37H46N204, found m/ e 582.7 (1%").

 

Benzyl 5-acetoxymethyl-3-methyl-4—octylpyrrole—2-carboxylate (110)
(39.9 g, 0.1 mol) was treated with 70% aqueous acetic acid as described for the
dipyrrylmethane (111) to give the title compound (51.7 g, 78%): m.p. 96-97 °C;
1H NMR (CDC13) 8 0.87 (6H, t, octyl Me), 1.28 (20H, m, CH;), 1.37 (4H, m, CH2),
226 (6H, s, 4,4'-Me), 2.35 (4H, t, 3,3'-CHz), 3.79 (2H, t, 2,2'-methylene), 5.21 (4H,
s, mC6H5), 7.30 (10H, m, phenyl protons), 9.07 (2H, br 5, NH); MS for
C43H53N204, found m/ e 666.3 (Mt).

 

5,5'-Dibenzyloxycarbonyl-4,4'-dimethyl-3,3'-dipentyl-2,2'-dipyrrylme-

thane (111) (29.1 g, 0.05 mol) was dissolved in freshly distilled tetrahydrofuran

138

(350 mL) containing a few drops of triethylamine. 10% Palladium/ carbon (0.5
g) was added and the reaction mixture was hydrogenated under hydrogen (1
atm., at room temperature) until hydrogen uptake ceased. The solvent was
evaporated and dried under vacuum without removing carbon by filtration
because 5,5'-dicarboxylic acid analogue (114) is partially soluble in
tetrahydrofuran. The dried reaction mixture, which contains the dicarboxylic
acid analogue (114) and catalyst carbon, was added in a mixture of 98-100%
formic acid (150 mL) and bromine (10 mL) in small portions. The reaction was
accomplished by stirring at room temperature for addition an additional one
hour after the addition, and then carbon was filtered off and washed with
formic acid. Most of formic acid was removed under reduced pressure and
the resulting solid was rinsed with cyclohexene and hexane to give the title
compound as violet crystals (23.7 g, 82% yield): m.p. 179-182 0C; M5 for
C21H31N2Br3, found m/ e 471.2 (M+).

 

5,5'-Dibenzyloxycarbonyl-4,4'.dimethyl-3,3'-dioctyl-2,2'-dipyrrylme-
thane (112) (33.3 g, 0.05 mol) was hydrogenated and then treated with bromine

by following the method described before for the dipyrromethenium bromide
(115) to give the title compound (26.1 g, 82%): m.p. 180-182 °C; M5 for
C27H43N2Br3, found m/ e 555.3 (Mt).

WW2)
DL-Alanine (35.1 g, 0.39 mol), pyridine (159 mL, 1.98 mol) and acetic

anhydride (224 mL, 235 mol) were mixed and heated on a steam bath with

stirring until a clear solution was formed. This orange-brown solution was

139

then heated for additional six hours. After the reaction was completed, excess
pyridine, excess acetic anhydride and formed acetic acid were removed under
vacuum. The dark residue (about 50 mL) was distilled through a fractional
column under reduced pressure to yield the title compound as a light yellow
liquid (41 g, 88%): b.p. 110-125 °C/ 3 mm.

3;Ammgnio-2-butanone chloride (118)
3-Acetamido-2-butanone (117) (41 g, 0.31 mol) dissolved in 35%

hydrochloric acid (400 mL) was heated to reflux for 8 hours, cooled to room
temperature and then filtered. The filtrate was evaporated to dryness under
vacuum to yield a yellow—brown residue which was washed with plenty of
acetone to give the title compound as a white powder (34.5 g, 88%): MS of
C4H9NOC1, found m/ e 8.71 (Mt).

th carbon 1 -4 dim th 1 le-2-carbo li a '

Hydrochloric acid (10%, 11.2 mL) was added to 3-ammonio—2-butanone
chloride (118) (16 g, 0.13 mol) dissolved in water (224 mL). This solution was
slowly added to a stirred solution of diethyl oxalacetate sodium salt (10 g) in
water (15 mL) and aqueous sodium hydroxide (10%, 15 mL) with heating on a
steam bath. During the addition, the title compound precipitated out. After
the reaction was completed, the reaction mixture was diluted with water (50
mL) and acidified with 10% hydrochloric acid until all the pyrrole precipitated
out. The white solid was collected by filtration, washed intensively with
water and dried in air to yield the title compound (10.2 g, 37%): m.p. 203-205
0C ; 1H NMR (CDC13) 8 1.42 (3H, t, COZCHgflg), 2.18, 2.26 (3H, s, 4,5-Me), 4.44
(2H, q, COLQHZCHB), 10.22 (1H, br 5, NH), 13.25 (1H, br s, -C02H); MS for
C10H13NO4, found m/ e 211.2 (Mi).

140

Eth car n l -4 dimeth l ole

3-(Ethoxycarbonyl)-4,5-dimethylpyrrole-2-carboxylic acid (119) (21.1 g,
0.1 mol) was mixed with sodium acetate trihydrate (50 g) and potassium
acetate (50 g). This powdery mixture was heated in an oil bath between 140 oC
and 160 0C until it was completely melted, cooled and stirred with water (200
mL) to precipitate product. The solid product was collected by filtration and
washed intensively with water to give the title compound as a pinkish brown
powder (15.7 g, 94%): m.p. 102-104 °C;1H-NMR (CDC13) 8 1.32 (3H, t,
001m), 2.17, 220 (3H each, s, 4,5-Me), 4.26 (2H, q, DQHZCHs), 8.23 (1H, s, a
proton), 8.86 (1H, br 5, NH); M5 for C911, 3N02, found m/e 167 (M'l').

&(Ethoxycarbonylz-Z-formyl-4,idimethylpyggle (121)
Phosphorus oxychloride (14 mL, 0.15 mol) was added dropwise to 3-

(ethoxycarbonyl)-4,5-dimethy1pyrrole (120) (16.7 g, 0.1 mol) dissolved in dry
N ,N-dimethylformamide (130 mL) in an ice bath under nitrogen. During the
addition, the reaction mixture was kept below 10 oC and then further stirred
for 2 hours at room temperature. The reaction mixture was diluted with
benzene (130 mL), stirred for 30 minutes and allowed to stand for a while.
The product was precipitated out by addition of water and a small amount of
aqueous sodium hydroxide (10%). The white solid was collected by filtration,
washed with water and dried in air to yield the title compound as white
crystals(10.9 g, 56%): m.p. 125-127 0C ;1H NMR (CDC13) 8 1.38 (3H, t, -CH7_(lI;),
222 228 (3H each, s, 4,5-Me), 4.37 (2H, q, -Qf_-1_2_CH3), 10.04 (1H, s, -CHO), 10.46
(1H, br 5, NH) ; MS for C10H13NO3, found m/ e 195 (M+).

 

bromide (123)
3-(Ethoxycarbonyl)-2~formyl-4,5-dimethylpyrrole (121) (7.80 g, 40 mmol)

and t-butyl 4-ethyl-3,5-dimethylpyrrole—Z-carboxylate (122) (8.92 g, 40 mmol)
were dissolved in methanol (100 mL) with warming. Hydrobromic acid (48%,
16 mL) was added dropwise to the stirred solution and the reaction mixture
was heated for 30 minutes on the steam bath during which time the solvent
was partially evaporated and some red crystals precipitated. It was then left
stand for 3 hours at room temperature. The precipitated solid was collected by
filtration, washed with methanol containing a few drops of hydrobromic acid
and dried in air. This crude product was purified by recrystallization from
dichloromethane and hexane to give the title compound as violet crystals
(14.1 g, 93%): m.p. 205-208 °C; 1H-NMR (CDCN3) 8 1.07 (3H, t, 4—C1-12Q13), 1.40
(3H, t, -OCH7_C_H_;), 2.21, 228, 2.58, 269 (3H each, s, 3, 4', 5, 5'-Me), 247 (2H, q, 4-
ngCHg), 4.37 (2H, q, wCHg), 8.23 (1H, s, methine), 13.37, 13.64 (1H each,
br 5, NH); MS for C13H25N202Br, found m/ e 301 (Mt).

12-eth 1-38 1218-te ameth 1-13 17-di n l h 'n-7-carbo la
5,5'-Dibromo-4,4'-dimethyl-3,3'-dipentyl-2,2'-dipyrrylmethenium
bromide (115) (5.51 g, 0.01 mol) and 3'-ethoxycarbonyl-4-ethyl-3,4',5,5'-
tetramethyl-2,2~dipyrrylmethenium bromide (123) (3.81 g, 0.01 mol) were
suspended in anhydrous formic acid (60 mL). To this reaction mixture ,
bromine (0.52 mL, 0.01 mol) was added and the mixture was heated to reflux
for 2 hours in an oil bath. The solvent was allowed to boil off over 4 hours
with a stream of air. Ethanol (100 mL) and concentrated sulfuric acid (2 mL)
were added to the dried reaction residue, followed by addition of triethyl

orthoformate (10 mL). After standing overnight, protected from moisture,

142

the reaction mixture was diluted with dichloromethane (150 mL) and then
neutralized with saturated aqeous sodium acetate (100 mL). The organic layer
was separated, washed once again with saturated aqueous sodium acetate(60
mL) and then three times with water (100 mL). After evaporation of the
solvent, the residue was chromatographed on silica gel column with
dichloromethane-hexane (2:1) as eluent. A dark non-fluorescent forerun was
discarded and the moving porphyrin band on chromatography column can be
monitored by using an UV-lamp to ensure a complete collection. The
fractions containing porphyrin were combined, evaporated to dryness under
vacuum, and then crystallized from dichloromethane and methanol to give
the title compound as sparkling purple crystals (0.84 g, 14%): 1H NMR
(CDC13) 8 -3.98 (2H, br 5, NH), 0.84, 0.85 (3H each, t, pentyl Me), 1.47 (8H, m,
CH2), 1.68 (4H, m, CH2), 1.84 (3H, t, 2-CI-Izgié), 221, 2.24 (2H each, t, 13.17-
CHz), 3.47, 3.47, 3.60, 3.82 (3H each, 5, ring Me), 3.88 (3H, t, CQCHZCLIQ), 4.04
(2H, q, Z-CflgCI-Ig), 4.88 (2H, q, C07Q1__2_CH3), 9.78, 9.85, 9.94, 11.01 (1H each, s,
meso H); UV-vis (in 10% CH3OH/CH2C12) lmax (EM) 630 nm (1,600), 573
(8,100), 547 (13,400), 509 (9,100), 406 (168,000); M5 for C39H50N4Oz, found m/ e
606.3 (M+).

lZ—eth l- 8121.- - ameth l-1 17—o-n-iolo h ' -7-carbo lat

5,5'-Dibromo-4,4'-dimethyl-3,3'-dioctyl-2,2'-dipyrrylmethenium
bromide (116) (6.35 g, 0.01 mol) and 3'-ethoxycarbonyl-4-ethyl-3,4',5,5'-
tetramethyl-2,2'-dipyrrylmethenium bromide (123) (3.81 g, 0.01 mol) were
treated with bromine and then oxidized in air following the method
described for the porphyrin (124) to give the title compound as sparkling
purple crystals (0.83 g, 12%): 1H NMR (CDC13) 8 -3.99 (2H, br 5, NH), 0.86, 0.87
(3H each, t, octyl Me), 1.29 (16H, m, CH2), 1.49, 1.70 (4H each, m, CH2), 1.83 (3H,

143

t, ZCHzgfié), 2.20, 2.22 (2H each, 1:, 13,17-CH2), 3.48, 3.48, 3.60, 3.83 (3H each, 5,
ring Me), 3.88 (3H, t, COZCHZQIQ), 4.03 (2H, q, Z-Qfl;CH3), 4.88 (2H, q,
COzgflgCHa), 9.77, 9.84, 9.92, 10.99 (1H each, s, meso H); UV-vis (in 10%
CH3OH/CH2C12) lmax (EM) 630 nm (1,600), 573 (8,100), 547 (13,400), 509 (9,100),
406 (168,000); M5 for C45H62N4Oz, found m/ e 690.3 CM").

 

Ethyl 2-ethyl-3,8,12,18-tetramethyl-13,17-dipentylporphyrin-7-
carboxylate (124) (61 mg, 0.1 mmol) was dissolved in pyridine (20 mL) with
heating and aqueous potassium hydroxide (5%, 4 mL) was then added. The
reaction mixture was heated under reflux for one hour or until the hydrolysis
was completed which was monitored by TLC. After hydrolysis, the reaction
mixture was diluted with water (100 mL) and neutralized with acetic acid
until the acid product precipitated and then filtered through a bed of Celite.
The product was extracted from the Celite with formic acid and the filtrate
was evaporated to dryness under vacuum to give the acid porphyrin (126).
Without purification, this acid product was suspended in dry
dichloromethane (30 mL) and then oxalyl chloride (0.1 mL, 1.1 mmol) was
slowly added in an ice bath. After the chlorination by stirring for one hour at
room temperature, the solvent was removed under vacuum to give the
carbonyl chloride porphyrin (128). Without isolation, this product (128) was
dissolved in dry dichloromethane (30 mL) and then N,N-
dimethylethylenediamine (0.02 mL, 0.18 mmol) was slowly added in an ice
bath. After stirring for one hour at room temperature, the solvent was
evaporated to dryness under high vacuum to remove excess N,N-

dimethylethylenediamine. The resulting residue was chromatographed on

144

silica gel with 15% methanol in dichloromethane. The desired compound
was collected to give the title compound (51.8 mg, 80%): 1H NMR (CDC13) 8
0.93, 0.94 (3H each, t, pentyl Me), 1.48, 1.67 (6H each, m, CH2), 1.81 (3H, t, 2-
CHzgl-IQ), 218, 2.21 (2H each, t, 13.17-CH2), 2.41 (6H, s, NMez), 281 (2H, t,
NHCHzgflgN), 3.37, 3.41, 3.46, 3.54 (3H each, 5, ring Me), 3.86 (2H, m,
NHQQCHzN), 3.99 (2H, q, 2-ggCH3), 7.39 (1H, t, COflflCHz), 9.73, 9.79, 9.85,
10.32 (1H each, s, meso H); UV-vis (in CH2C12) kmax (SM) 622 mm (1,600), 568
(6,800), 541 (11,200), 504 (10,200), 403 (166,000); M5 for C41H56N60, found m/ e
648.7 (NH).

7- N- 2- Dimeth lamin eth 1 carbamido -2-eth l- 8 12 1 tetrameth 1-13 17-
MW

Ethyl 2-ethyl-3,8,12,18-tetramethyl-13,17-dioctylporphyrin-7-carboxylate
(125) (69 mg, 0.1 mmol) was hydrolized with potassium hydroxide in pyridine
and then chlorinated with oxalyl chloride and treated with N,N-
dimethylethylenediamine following the method described for the porphyrin
amide (130) to give the title compound (59.3 mg, 81%): 1H-NMR (CDC13) 8
0.93, 0.95 (3H each, t, octyl Me), 1.27 (16H, m, 012), 1.47, 1.68 (4H each, m, CH2),
1.82 (3H, t, 2-CHZQLIQ), 219, 222 (2H each, t, 13, 17-CH2), 2.42 (6H, s, NMez),
282 (2H, t, NHCHzg-IQN), 3.38, 3.42, 3.47, 3.55 (3H each, 5, ring Me), 3.87 (2H,
m, NH§I_-I_2_CH2N), 4.00 (2H, q, 2-QI_<I;CH3), 7.40 (1H, t, CON__H), 9.72, 9.79, 9.85,
10.31 (1H each, s, meso H); UV-vis (in 10% CH3OH/CH2C12) km“ (8“) 622 nm
(1,600), 568 (6,800), 541 (11,200), 504 (10,200), 403 (166,000); MS for C47H63N50,
found m/ e 733.1 (Mt).

 

 

I45

7- - 2- rimeth lammonio eth l carbamido -2 th 1- 12 18-tetram th 1-
17 i n1 h 'niodie
7—{N-[2-(Dimethylamino)ethyl]carbarnido}-2-ethyl-3,8,12,18-

tetramethyl-13,17-dipentylporphyrin (130) (45.4 mg, 0.07 mmol) was dissolved
in dichloromethane (35 mL) containing 10% methanol and iodomethane
(0.044 mL, 0.7 mmol) was then added. The reaction mixture was stirred for 5
hours at room temperature and the solvent was evaporated to dryness under
vacuum to give the title compound in almost quantitative yield: UV-vis (in
10% CH3OH/CH2C12) Amax (SM) 623 nm (1,600), 569 (7,000), 542 (11,400), 505
(9,400), 403 (164,000); M5 for C42H59N601, found m/ e 663.7 (Mt).

7- N- 2- Trimeth lammoni eth lcarbamid -2 h l- 12 18- trameth l-
17- i l h ' i di e
7-{N-[2-(Dimethylamino)ethyl]carbamidol-Z-ethyl-3,8,12,18-

tetramethyl-13,17-dioctylporphyrin (131) (51.3 mg, 0.07 mmol) was treated
with excess iodomethane following the procedure described for the
ammonium derivative (132) to give the title compound in almost
quantitative yield: UV-vis (in 10% CH30H/CH2C12) Xmax (EM) 623 11111 (1,600),
569 (7,000), 542 (11,400), 505 (9,400), 403 (164,000); MS for C48H71N601, found
m/ e 748.1 (M+).

 

lat

Osmium tetroxide (115 mg, 0.45 mmol) and pyridine (0.05 mL) were
added to ethyl 2-ethyl-3,8,12,18-tetramethyl-13,17—dipentylporphyrin-7—
carboxylate (124) (182 mg, 0.3 mmol) dissolved in dichloromethane (40 mL).

After the reaction mixture was stirred for 24 hours at room temperature

 

146

under nitrogen in the dark, it was quenched by adding methanol (10 mL),
then bubbled with hydrogen sulfide through the reaction solution for 30
minutes to decompose the osmate adduct, and allowed to stand for 2 hours.
The precipitated black osmium sulfide was removed by filtration through a
bed of Celite and the filtrate was evaporated. The resulting residue was
dissolved in dichloromethane (50 mL) and perchloric acid (70%, 0.8 mL) was
added and then stirred for 30 minutes at room temperature. The reaction
mixture was diluted with dichloromethane (50 mL) and the organic layer was
washed twice with saturated aqueous sodium acetate (50 mL) and twice with
water (50 mL). The organic layer was dried over anhydrous sodium sulfate
and the solvent was removed under vacuum and the residue was
chromatographed on silica gel with dichloromethane as eluent. The
porphyrinone [84] (65.3 mg, 35%) was isolated as the major product: 1H NMR
(CDC13) 8 -2.77 (2H, br s, NH), 058, 0.98 (3H each, t, pentyl Me), 0.99, 1.13, 1.13,
1.52, 1.65, 2.14 (2H each, m, CH2), 1.75 (3H, t, 2-CHZQI-la), 1.83 (3H, t,
COzCHZQL-Ig), 2.13 (3H, s, 18-Me), 274 (2H, t, 18012), 3.26, 3.54, 3.54 (3H each, 5,
ring Me), 3.80 (2H, t, 1341112), 3.98 (211, q, 243391-13), 4.78 (2H, q, COflngI‘h),
9.07, 9.59, 9.68, 10.76 (1H each, s, meso H); UV-vis (in CH2C12) kmax (SM) 634
nm (14,400), 561 (16,600), 524 (7,700), 412 (168,000), 319 (15,800); M5 for
C39H50N4O3, found m/ e 622.7 (M‘l’).

7- N- 2- Dimeth lamin eth l arbamido -2 th l- 12 18-tetrameth 1-1 18-
g'pentyl-W-pggphm'ngng (135)

Ethyl 2-ethyl-3,8,12,18-tetramethyl-13,18-dipentyl-17-porphyrinone-7-
carboxylate (134) (622 mg, 0.1 mmol) was treated with potassium hydroxide,
with oxalyl chloride and with N,N-dimethylethylenediamine following the
method described for the porphyrin amide (130) to afford the title compound

 

147

(51.6 mg, 77.7%): 1H NMR (CDC13) 8 -2.89 (2H, br 5, NH), 0.53, 0.93 (3H each, t,
pentyl Me), 0.94, 1.09, 1.09, 1.50, 1.66, 2.58 (2H each, m, CH2), 1.79 (3H, t, 2-
CHLCfla), 2.07 (3H, s, 18-Me), 217 (2H, q, NHCHzCHzN), 2.48 (6H, s, NMez),
272 (2H, t, NHCHfiL-IJN), 293 (2H, t, 18-CHz), 3.35, 3.52, 3.55 (3H each, 5, ring
Me), 3.88 (2H, t, 13-CH2), 4.00 (2H, q, Z-gfizCHg), 7.46 (1H, br s, CONH), 9.08,
9.66, 9.73, 10.29 (1H each, s, meso H); UV-vis (in 10% CHzClz/ CH2C12) 1m“
(8“) 634 nm (13,900), 578 (9,300), 561 (16,100), 524 (7,300), 412 (165,000); M8 for
C41H56N602, found m/ e 664.7 (M+).

7- N- 2- rimeth lammonio eth l carbamido -2-eth l-3 8 12 18-tetrameth l-
13,18-dipengl-17-pgrphm'none iodide (136)

7-(N-[2-(Dimethylamino)ethyl]carbamidol-Z-ethyl-3,8,12,18-
tetramethyl-13,18-dipentyl-17—porphyrinone (135) (46.5 mg, 0.07 mmol) was
treated with excess iodomethane following the method described for the
ammonium derivative ((132) to give the title compound in almost
quantitative yield: UV-vis (in 10% CH3OH/CH2C12) 1m (8”) 635 nm (13,900),
579 (9,300), 561 (16,100), 525 (7,300), 413 (165,000); M5 for C42H59N6021, found
m/ e 679.6 (M+).

Nickelfll) 23,7812,13,17,18-octaethylmgphm'n (138)

some excess nickel (II) hexahydrate was added to a solution of
octaethylporphyrin (137) (1.07 g, 2.00 mmol) in N,N-dimethylformamide (50
mL). The mixture was heated to reflux for one hour and then allowed to
evaporate two thirds of N,N-dimethylformamide without condenser. After
standing one hour, crystallized product was collected by filtration and washed
with methanol to give the title compound as red-purple sparkling crystal (1.17
g, 98.7%): 1H NMR (CDC13) 8 1.81 (24H, t, -CH2(_I_I-Lg,_), 3.92 (16H, q,

148

CHZCHg),9.77 (4H, s, meso H); UV-vis (in CH2C12) lmax (rel. int.) 551 nm
(38.0), 516 (12.7), 391 (221.8), 329.5 (16.0); M5 for C36H44N4Ni, found m/e 591.3
(M+).

Coppergm 2;,7,8,12,13,17,18-octaethylpggphm‘n (132)
Octaethylporphyrin (137) (1.07 g, 2.0 mmol) was dissolved in mixture of

dichloromethane (100 mL) and methanol (25 mL) and then a solution of
copper (II) acetate monohydrate (0.60 g, 3.0 mmol) was added. After the
mixture was refluxed for 20-30 minutes, it was washed several times with
water. The organic solution was dried over anhydrous sodium sulfate and
the solvent was evaporated under vacuum to give the title compound (1.18 g,
98.9%): UV-vis (in CH2C12) kmax (rel. int.) 560 nm (10.3), 522 (5.3), 397 (147.5),
326 (8.0); MS for C36H44N4Cu, found m/ e 596.2 (Mt).

Nickel 10- 2-form lethen 1-2 78121 1718-octaeth l h
3-(Dimethylamino)acrolein (3.0 mL, 30 mol) was added to a solution of
nickel(II) complex of 2,3,7,8,12,13,17,18-octaethylporphyrin (138) (1.78 g, 3.0
mol) in dry dichloromethane (200 mL) at room temperature. Phosphorus
oxychloride (2.83 mL, 30 mol) was added dropwise to the reaction mixture
with continuous stirring, at 0 °C. The final mixture was stirred at room
temperature for 10 hours and then treated with saturated aqueous sodium
carbonate (300 mL) overnight. The mixture was extracted with
dichloromethane and the combined organic layers were washed three times
with water (300 mL). The solution was dried over anhydrous sodium sulfate
and the solvent was removed under vacuum. The resulting residue was
chromatographed on silica gel with hexane-dichloromethane (1:2) as eluent

and the desired compound was collected and recrystallized from

149

dichloromethane and methanol to give the title compound (1.68 g, 87%): m.p.
245-246 0C; 1H NMR (CDC13) 8 1.65-1.77 (24H, overlapping t, peripheral
CHygflz),13.7O-3.80 (16H, overlapping q, peripheral §I_-I;_CH3), 5.50 (1H, dd,
-CH=QI-_I_-CHO), 9.34 (3H, s, meso H), 9.67 (1H, d, -CH=§fl-CHO), 9.82 (1H, d,
CHO); UV-vis (in CH2C12) lmax (EM) 582 nm (17,200), 564 (17,900), 536 (15,850),
406 (70,800); MS for C39H45N4NiO, found m/ e 644 (M+).

Coppergm 10-(2-formylethenyl)-2,3,7.8,12,13.17,18—Qctaethylporphm’n (141)

3-(Dimethy1amino)acrolein (0.17 mL, 1.7 mmol) was added to copper
(II) octaethylporphyrin (139) (100 mg, 0.17 mmol) dissolved in dry
dichloromethane (20 mL) at room temperature and then treated with
phosphorus oxychloride (0.16 mL, 1.7 mmol), following the method described
for compound (140) before, to give the title compound (64 mg, 58%): m.p. 230-
232 °C; UV-vis (in CH2C12) lmax (SM) 568 nm (14,200), 534 (12,100), 408
(139,500), 331 (22,100); MS for C39H44CuN4O, found m/ e 648.3 (M+).

2 121 171 aehl nz hlrin

Nickel(II) complex of 10-(2-formylethenyl)-2,3,7,8,12,13,17,18-
octaethylporphyrin (140) (1.29 g, 2.0 mmol) was dissolved in 18 (v/v)%
sulfuric acid in trifluoroacetic acid (35 mL). The reaction solution was
bubbled with hydrogen sulfide for one hour at room temperature before being
poured into ice/ water (150 mL). The mixture was extracted with
dichloromethane, and the combined organic layer was washed with saturated
aqueous sodium carbonate and finally with water. The organic solution was
dried over anhydrous sodium sulfate, the solvent was removed under
vacuum, and the resulting residue was chromatographed on silica gel with

hexane-dichloromethane (3:2) as eluent. The desired green band was

150

collected and crystallized from dichloeomethane and methanol to give the
title compound (0.94 g, 82%). This compound can be obtained from crude
nickel(II) 10-(2-formylethenyl)-octaethy1porphyrin (140), without purification,
by the same procedure described above. The overall yield of reaction from the
nickel(II) octaethylporphyrin (138) to the free base octaethylbenzochlorin (142)
was 73%: m.p. 241-243 0C; 1H NMR (CDC13) 8 0.02 (6H, t, gem CH3), 1.55-1.87
(18H, overlapping t, peripheral CH3), 261 (4H, overlapping q, gem CH2), 3.45-
3.93 (12H, overlapping q, peripheral CH2), 8.03 (1H, d, H of benzene ring), 8.10
(1H, t, H of benzene ring), 8.01, 8.56, 9.22 (1H each, s, meso H), 9.51 (1H, d, H of
benzene ring); UV-vis (in CH2C12) kmax (EM) 658 (35,000), 605 (17,000), 564
(15,400), 532 (13,700), 411 (107,500); MS for C39H43N4, found m/ e 572 (M1).

Nickel 2 8 12 13 17 1 aeth lbenzochlorin

(i) From 2,3,8,8,12,13,17,18-octaethylbenzochlorin (142). Some excess
nickel(II) chloride hexahydrate was added to a solution of
octaethylbenzochlorin (142) (0.58 g, 1.0 mmol) in N,N-dimethylformamide
(25 mL) and heated to reflux. Reaction progress was monitored by
spectrophotometry. The reaction mixture was then diluted with
dichloromethane (40 mL), washed with water to remove excess nicked
chloride, dried over anhydrous sodium sulfate, and evaporated to dryness.
The residue was chromatographed on silica gel with
dichloromethane/ hexane (1:1). The desired green band was collected and
crystallized from dichloromethane and methanol to yield the title compound
as shining crystals (0.60 g, 95%) i

(ii) From nickel(II) 10-(2-formylethenyl)-2,3,7,8,12,13,17,18-
octaethylporphyrin (140). Nickel(II) formylethenylporphyrin (140) (200 mg,

0.31 mmol) was treated with concentrated sulfuric acid (15 mL) at room

151

temperature for 1.5 hours. The reaction was poured into ice/ water (300 mL)
and extracted with dichloromethane. The organic layers were combined,
washed with saturated aqueous sodium bicarbonate and with water, dried
over anhydrous sodium sulfate, and the solvent was removed under
vacuum. The residue was purified by the method described above to yield the
title compound (92 mg, 47%).

For the title compound: m.p. 224-225 °C ; 1H NMR (CDC13) 8 0.01 (6H,
t, gem CH3), 1.60-1.87 (18H, overlapping t, peripheral CH3), 2.62 (4H,
overlapping q, gem CH2), 3.48-3.93 (12H, overlapping q, peripheral CHz), 8.02
(1H, d, H of benzene ring), 8.10 (1H, t, H of benzene ring), 8.01, 8.56, 9.22 (1H
each, s, meso H), 9.53 (1H, d, H of benzene ring); UV-vis (in CH2C12) 1W (8M)
670 nm (20,000), 618 (6,800), 564 (4,200), 415 (37, 100); M5 for C39H45N 4N i,
found m/ e 628 (Mt).

r11 23 8121 1718 eth lbenz orin

A solution of copper(II) acetate monohydrate (0.40 g, 2.0 mol) in
methanol (7 mL) was added to a solution of 2,3,8,8,12,13,17,18-
octaethylbenzochlorin (142) (0.63 g, 1.1 mmol) in dichloromethane (60 mL)
and methanol (20 mL). After the reaction mixture was refluxed for 20
minutes, it was washed several times with water. The solution was dried
over anhydrous soduim sulfate and the solvent was removed under
vacuum. The resulting residue was chromatographed on silica gel with
hexane-dichloromethane (1:1). The desired product was collected and
recrystallized from dichloromethane/ methanol to give the title compound
(0.68 g, 97.5%): UV-vis (in CH2C12) lmax (EM) 670 nm (18,500), 620 (5,100), 563
(2,100), 519 (2,400), 418 (37,100); M5 for C39H46N4Cu, found m/ e 633 (M1).

 

152

Copperfll) IQ-(N,N-dimethy1iminium)-2,3,§,8,12,13,17,18-octagthylbenzo-
chlorin chloride (142)

Copper(II) 2,3,8,8,12,13,17,18-octaethylbenzochlorin (144) (0.61 g, 0.96
mmol) was dissolved in a mixture of dry dichloromethane (100 mL) and
N,N-dimethylformamide (1.2 mL, 15 mmol) was added. Phosphorus
oxychloride (1.1 mL, 11 mmol) was added dropwise to the reaxtion mixture
with continuous stirring at room temperature. The final mixture was stirred
for 18 hours at room temperature and washed with diluted sodium
bicarbonate. The organic layer was washed with a large amount of water and
dried over anhydrous sodium sulfate, and the solvent was removed under
vacuum. The resulting residue was chromatographed on silica gel with 10%
methanol in dichloromethane as eluent to give the title compound (0.54 g,
77.5%): UV-vis (in CH2C12) Xmax (SM) 752 nm (35,000), 690 (12,000), 570 (7,000),
448 (30,000), 386 (51,000); M5 for C42H52N5CuCl, found m/ e 689.3 (M+).

1 N Jimeh liminium- 3 : 8121 171:..- tae lbenz. 1. 'n loo-r'
(145.)

Copper(II) 10-(N,N-dimethyliminium)-2,3,8,8,12,13,17,18-octaethyl-
benzochlorin chloride (147) (0.73 g, 1.0 mmol) was stirred in concentrated
sulfuric acid (15 mL) for 5 hours. The mixture was poured into ice/ water (100
mL), neutralized with aqueous sodium bicarbonate, and then extracted with
dichloromethane. The organic layer was washed three times with water,
dried over anhydrous sodium sulfate, and evaporated under vacuum. The
resulting residue was chromatographed on silica gel with 10% metanol in
dichloromethane, and the desired green band was collected to give the title

compound (0.49 mg, 78%). If the same proudure as above was used to treat

153

the crude copper(II) dimethyliminium, benzochlorin (147), the yield from the
copper(II) octaethylbenzochlorin (144) to the title compound (145) was 62%.

For the title compound: 1H NMR (CDC13) 8 -0.09, 0.11 (3H each, t, gem
CH3), 1.30-1.60 (18H, overlapping t, peripheral CH3), 2.53-2.75 (4H, m, gem
CH2), 2.77, 4.32 (3H each, s, NMez), 3.16-3.47 (12H, overlapping q, peripheral
CH2), 5.78 (2H, br s, NH),'7.81 (1H, d, H of benzene ring), 7.81 (1H, t, H of
benzene ring), 8.26, 8.53 (1H each, s, meso H), 8.78 (1H, d, H of benzene ring),
10.31 (1H, br s, QH=NMe2); UV-vis (in CH2C12) kmax (SM) 797 nm (49,000), 606
(9,670) 387 (52,300); MS for C42H54N 5C1, found m/ e 628.4(M+).

Nigkel(H) 10-(N,N-dimethyliminium24.388.12.13,17,1§-Qctaethylbenzo-
gflgrin Qlofide (146)

(i) From 10-(N,N-dimethyliminium)-2,3,8,8,12,13,17,18-octaethylbenzo-
chlorin chloride (145). Some excess nickel (II) acetate was added to a solution
of dimethyliminium octaethylbenzochlorin (145) (66.4 mg, 0.1 mmol) in
acetic acid (35 mL) and refuxed. Reaction progress was monitored by
spectrophotometry. After 6 hours, the reaction mixture was diluted with
dichloromethane (80 mL), washed with water and brine to remove excess
nickel(II) chloride, and dried over anhydrous sodium sulfate. After removal
of the solvent, the crude product was chromatographed on silica gel with 10%
methanol in dichloromethane to yield the title compound (63.6 mg, 93%).

(ii) From nickel(II) 2,3,8,8,12,13,17,18-octaethylbenzochlorin (143). N .N—
Dimethylformamide (1.2 mL, 15 mmol) was added to nickel(II)
octaethylbenzochlorin (143) (62.9 mg, 1.0 mmol) dissolved in dry
dichloromethane (100 mL). Phosphorus oxychloride (1.1 mL, 11 mmol) was
added dropwise to the reaction mixture with continuous stirring at room

temperature. The reaction mixture was stirred overnight at room

154

temperature, diluted with dichloromethane, and treated with diluted
aqueous sodium bicarbonate. The organic layer was washed with water and
brine, and dried over anhydrous sodium sulfate. Evaporation of the solvent
gave a residue which was purified as above to yield the title compound (62.3
mg, 91%).

For the title compound ; 1H NMR (CDC13) 8 0.01, 0.08 (3H each, t, gem
CH3), 1.22-1.45 (18H, overlapping t, peripheral CH3), 2.35-2.60 (4H, m, gem
CH2), 2.69, 4.13 (3H each, s, NMez), 2.93-3.24 (12H, overlapping q, peripheral
CH2), 7.61 (1H, d, H of benzene ring), 7.61 (1H, t, H of benzene ring), 7.75, 7.97
(1H each, s, meso H), 8.33 (1H, d, H of benzene ring), 9.86 (1H, s, -§_Ii=NMe2);
UV-vis (in CH2C12) lmx (EM) 773 nm (46,200), 588 (13,600), 452 (47,400), 393
(80,600), 321 (34,500); MS for C42H52N5NiCl, found m/ e 684.4 (M+).

Zinc 1 - NN-dimeth liminium -2 12 1 1718- ae h lb nz l rin
ohlorido (148)

A solution of zinc acetate dihydrate (30 mg, 0.13 mmol) in methanol
(10 mL) was added to a solution of 10-(N,N-dimethy1iminium)-
2,3,8,8,12,13,17,18-octaethylbenzochlorin chloride (145) (30 mg, 0.045 mmol) in
chloroform (40 mL). The reaction mixture was heated to reflux until zinc
insertion was completed which was monitored by spectrophotometry. The
reaction mixture was diluted with chloroform (30 mL), washed with water to
remove excess zinc acetate, dried over anhydrous sodium sulfate, and
evaporated to dryness under vacuum. The residue was purified by
preparative thick layer plates (silica gel) eluted with 8% methanol in
dichloromethane. The product, extracted from the silica gel, was crystallized
from dichloromethane-hexane to give the title compound (25 mg, 76%): UV-

 

155

vis (in CHzClz) kmax (EM) 739 nm (51,300), 679 (17,800), 574 (6,200), 448 (35,500),
383 (65,000), 321 (31,700); M5 for C42H52N52nC1, found m/ e 692.2 (M+).

10-(N.N-Dimethyliminium)-2,3,8,8,12,13.17,18 octaethylbenzochlorin-52:
sulfonic acid chloride (142)

Nickel(II) 10-(N,N-dimethyliminium)-2,3,8,8,12,13,17,18-octaethy1-
benzochlorin chloride (146) (68.5 mg, 0.1 mmol) was stirred in concentrated
sulfuric acid (3 mL) for 4 days at room temperature. The resulting solution
was then poured into an ice-cold saturated aqueous sodium bicarbonate and
extracted with dichloromethane. The organic layer was separated, washed
with water, dried over anhydrous sodium sulfate, and evaporated. The
residue was purified by column chromatography using 8% methanol in
dichloromethane. The free base octaethylbenzochlorin iminium salt (145)
was isolated from the first green band in 40% yield (26.5 mg). A second band
which was the free base octaethyl sulfonated benzochlorin iminium salt
derivative (149) was isolated with 12% methanol in dichloromethane. It was
crystallized from dichloromethane—hexane to afford the title compound (29.6
mg, 40%): 1H NMR (CD3CN) 8 -0.08, 0.13 (3H each, t, gem CH3), 122-1.62 (18H,
overlapping t, peripheral CH3), 2.42-2.81 (4H, m, gem 012), 271 (3H, s, N-
CH3), 319-3.49 (12H, overlapping g, peripheral 012), 3.79 (3H, s, N—CI-Ig), 5.75
(2H, br 5, NH), 8.25 (1H, s, H of benzene ring), 8.40, 8.63 (1H each, s, meso H),
9.33 (1H, s, H of benzene ring), 9.37 (1H, s, -_(_I_I_1_=NMe2); UV-vis (in 10%
MeOH/ CH2C12) lmax (EM) 803 nm (33,800), 615 (9,800), 389 (55,400); M5 for
C42H54N5503Cl, found m/ e 708 (Mt).

156

Zin II 10— N N-dimeth liminium -2 8 12 1 17 18- taeth lbenzochlorin-
52-sulfonic acid chloride (151)

The sulfonic acid iminium chloride (149) was treated with zinc acetate
dihydrate following the method described before for the zinc (II) iminium
derivative (148) to give the title compound in 76% yield after crystallization
from dichloromethane-hexane: 1H NMR (CD3CN) 8 0.10, 0.20 (3H each, t,
gem CH3), 1.10-1.52 (18H, overlapping t, peripheral CH3), 2.30-2.80 (4H, m,
gem CH2), 280 (3H, s, N-CH3), 3.00-3.20 (12H, overlapping q, peripheral CH2),
3.65 (3H, s, N-CH3), 7.95, 8.11, 8.15, 8.85 (1H each, s, meso H and H of benzene
ring), 9.35 (1H, s, -§_I-1=NMe2); UV-vis (in CH2C12) lmax (EM) 744 nm (36,400),
682 (14,100) 570 (5,600), 449 (31,900), 384 (60,100); M5 for C42H52N55032nC1,
found m/ e 772 (M+). ‘

NickolflI) 10-formyl-2,§,8,§,12,13.17.IMaethyloonzoohlorin (152)
Nickel(II) 10-(N,N-dimethyliminium)-2,3,8,8,12,13,17,18-octaethyl-

benzochlorin chloride (146) was dissolved in dichloromethane and stirred
with saturated aqueous sodium carbonate for one day to give the title
compound in more than 90% yield: 1H NMR (CDC13) 8 0.12 (6H, t, gem CH3),
1.36-1.50 (18H, overlapping t, peripheral CH3), 2.32, 282 (2H each, m, gem
CHz), 3.06-3.32 (12H, overlapping q, peripheral CH2), 7.56 (1H, d, H, of benzene
ring ), 7.89, 8.19 (1H each, s, meso H), 8.40 (1H, d, H of benzene ring), 10.64 (1H,
br s, -CHO); UV-vis (in CH2C12) kmax (rel. int) 710 nm (66.5), 439 (96.1), 406
(100), 371 (85.7); M5 for C401-I46N4Ni0, found m/ e 656.4 (M+).

1°9°N9ifl

10

11.

12.
13.
14.

15.

16.
17.

18.

19.

157

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