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SYNTHESIS OF MALE SEA LAMPREY PHEROMONES
VIA ALLOMERIZATIONS

presented by

SOONG-HYUN KIM

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SYNTHESIS OF MALE SEA LAMPREY PHEROMONES
VIA ALLOMERIZATIONS

By

Soong-Hyun Kim

A DISSERTATION

Submitted to
Michigan State University
in partial fulﬁllment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY
Chemistry
2010

Professor Robert E. Maleczka Jr.

ABSTRACT

SYNTHESIS OF MALE SEA LAMPREY PHEROMONES
VIA ALLOMERIZATIONS

By
Soong-Hyun Kim

3-Keto petromyzonol sulfate (3kPZS) and 3-keto allocholic acid (3kACA) are
potent components of the sex pheromone cocktail emitted by male sea lamprey,
petromyzon marinus. Such pheromones have been successfully tested as population
control agents against lamprey residing in the Great Lakes. Owing to these results, a
straightforward and practical synthetic route to 3kPZS and 3kACA is needed. For the
synthesis of 3kPZS and 3kACA, cholic acid was selected as the common starting
material, because cholic acid has the carbon skeleton and functionality suitable for 3kPZS
and 3kACA. Allomerization to convert the stereochemistry from SB (A/B cis) to 50¢
(A/B trans) was the crucial step in this synthesis. Several allomerizations were
conducted, including a single step allomerization with Raney Ni and a variety of stepwise
allomerizations. Crucial intermediate was successfully derived from a single step
allomerization with Raney Ni or stepwise allomerization from modiﬁed Birch reduction
protocol. A plausible synthetic route to male sea lamprey pheromones, 3kPZS and

3kACA was established from the crucial intermediate.

To Jungyoon and Taeho Kim

ACKNOWLEDGMENTS

Wrapping up the very important moment in my career, I really appreciate my life
here in East Lansing. I ﬁnally achieved and closed another chapter of my life as a
doctoral researcher. I need to acknowledge many people for my successful ﬁnale.

First of all, I would like to thank Professor Robert E. Maleczka, Jr. for being my
advisor. Without his guidance, I could not have made it. I have leamed a lot of things,
attitude as a scientist, development of critical insight about science, way to make
excellent chemistry class, way to make an approach to solve out scientiﬁc problems, and
especially presentation skills to ﬁnish and display my work to other people.

I would also like to thank Professor William Wulff, James Jackson, and Aaron
Odom for being my committee members and helping me ﬁnish within time through all
those rush. Helpful discussion and guidance to be a real chemist gave me such an
incredible experience for my achievement.

I wish to thank my colleagues from the Maleczka group for their friendship and
help. Spending their countless time and discussion on my research/literature/practice talk
made my presentation perfect.

All this achievement would not have been made without support and
encouragement of my family. I would like to thank my family members in Korea for
giving me a life, teaching me way to be good person, and guiding me to make a
reasonable thinking. Lastly, I wish to thank my wife and my son for giving me another
life as husband and father. Without Jungyoon’s belief in me and her endless love, I could

not have made it. I really appreciate it and I always love you, Jungyoon and Taeho.

iv

TABLE OF CONTENTS

LIST OF TABLES .................................................................................. vii
LIST OF FIGURES ................................................................................ viii
LIST OF SCHEMES ................................................................................. ix
CHAPTER I
INTRODUCTION ..................................................................................... 1
1.1. The Sea Lamprey in the Great Lakes ................................................... 1
1.2. Sea Lamprey Population Control in the Great Lakes ............................... 4
1.2.1. Current methods to control sea lamprey .................................... 4
1.2.2. Life cycle of sea lamprey and related pheromones ...................... 6
1.2.3. Application of pheromones to sea lamprey control ...................... 8
1.2.4. Isolation of sex pheromones for lamprey control agents .............. 10
1.3. Retrosynthetic Analysis ................................................................. 11
1.4. Prior Synthesis ............................................................................ 13
CHAPTER 2.
SINGLE STEP ALLOMERIZATION WITH RANEY NICKEL ............................. 22
2.1. Mitra and Elliot’s Allomerization with Raney Ni .................................. 22
2.1.]. Single step allomerization of methyl cholate ........................... 22
2.1.2. Mechanism of allomerization with Raney Ni ........................... 22
2.2. Optimization of Single Step Allomerization with Raney Ni .................... 26
2.3. Separation ofMixture of SB (A/B cis) 2 and 5a (A/B trans) 130
2.3. 1. Separation by liquid chromatography on neutral alumina ............ 30
2.3.2. HPLC separation of mixture of 513/50: carboxylic acids at C24 .....30
2.3.3. Kinetic resolution of 2/1 (5 B/Sa) mixtures .............................. 32
2.3.4. Separation of 2/1 (SB/5a) mixtures by gas chromatography . . . . . ....36
2.3.5. Resolution attempt of SB/Sa mixtures via sublimation ............... 37
CHAPTER 3.
STEPWISE ALLOMERIZATION .................................................................. 38
3.1. Oxidation at C3 Position of Cholic Acid Derivatives ............................. 38
3.2. Dehydrogenation with I(V) Reagents ................................................ 41
3.3. Stereoselective Reduction .............................................................. 46
3.3.1. Birch reduction ............................................................. 46
3.3.2. SET Reduction with SmIz ................................................ 50
3.3.3. SET Reduction with sodium dithionite (Na28204) .................... 51
3.3.4. Directed hydrogenation with Crabtree’s catalyst ...................... 54
3.3.5. Stereoselective reduction with in-situ Cu-H ........................... 55
3.3.6. Directed hydrogenation with Wilkinson’s catalyst .................... 56
3.3.7. Selective reduction via internal hydride delivery ..................... 58

CHAPTER 4.
SYNTHESIS OF MALE SEA LAMPREY PHEROMONES AND FUTURE STUDIES

......................................................................................................... 62
4.1. Synthesis of ACA ..................................................................... 62
4.2. Synthesis of 3kPZS ................................................................... 62
4.3. Synthesis of Larval Lamprey Pheromones, P23 and ACA ..................... 64
4.4. Conclusions and Future Studies ..................................................... 66

APPENDIX.

EXPERIMENTAL DETAILS ..................................................................... 71
General Materials and Methods ............................................................. 71
Standard Reaction Method ................................................................... 72
Methyl cholate 12 ............................................................................. 72
Representative Single Step Allomerization with Raney Ni (Scheme 10 & l 1) ...73
Separation of SB/Sa mixtures ............................................................. 75
Preparation of compound 2 with Fetizon’s Reagent (Scheme 18) ................... 76
Synthesis of Compound 41 .................................................................. 76
Representative Dehydrogenation with Iodic Acid (Scheme 21) ..................... 77
Representative Dehydrogenation with IBX (Scheme 22) ............................. 78
Representative Birch Reduction (Scheme 25) .......................................... 79
Modiﬁed Sequence of Birch Reduction (Scheme 26 & 27) .......................... 81
Representative Conjugate Reduction with Na28204 (Scheme 30) ................... 82
Synthesis of Compound 63 ............................................................... 83
Synthesis of Compound 59 ............................................................... 84
Synthesis of Compound 31 ............................................................... 85
Synthesis of Compound 66 ............................................................... 86
Preparation of 3kPZ ........................................................................ 87
Synthesis of 3kACA ....................................................................... 88
Synthesis of 3kPZS ........................................................................ 89
Tables for x-ray crystallography of mono-benzoylated compound 1 ............... 90

REFERENCES ..................................................................................... 105

vi

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

LIST OF TABLES

Crystal data and structure reﬁnement for m1112404 ................................ 90
Atomic coordinates (x104), equivalent isotropic displacement parameters

(A2x103), and occupancies for m1112404 ............................................. 92
Bond lengths [A] and angles [deg] for mll 12404 ................................... 94
Anisotropic displacement parameters (A2x103) for m1112404 .................... 99

Hydrogen coordinates (x104), isotropic displacement parameters (A2x103),
and occupancies for m1112404 ....................................................... 102

vii

LIST OF FIGURES

Figure 1. Sea lamprey, Petromyzon Marinus ....................................................... 1
Figure 2. Sea lamprey jawless mouth and sea lampreys feeding on trout ................... 2
Figure 3. Sea lamprey population in the United States and in the Great Lakes ............ 3
Figure 4. Chemical structure of bisazir ............................................................ 4
Figure 5. Chemical structures of lampricides ...................................................... 5
Figure 6. Lake trout populations and sea lamprey populations in Lake Superior ........... 5
Figure 7. Chemical structures of migratory pheromones from larval sea lamprey ......... 8
Figure 8. Chemical structures of sex pheromones from male sea lamprey ................... 9

Figure 9. Identiﬁed products ﬁom allomerization of methyl cholate by Raney Ni ........ 24

Figure 10. Three-dimensional structures of SB (A/B cis) ester 2 and derivatized 5a (A/B

trans) ester 1 based on their X-ray crystal structures ............................... 29
Figure 11. Separation of mixture of SB/Sa carboxylic acids at C24 on HPLC ............ 31
Figure 12. Three-dimensional structures of 5 B ester 2 and Son ester 1 ...................... 32
Figure 13. Newman projections of two 515 (A/B cis) compounds, 26 and 2 ............... 35
Figure 14. Separation of 2/1 (SB/50L) mixtures by gas chromatography ..................... 36
Figure 15. Sublimation attempt to separate SIB/Soc mixtures ................................... 37

viii

LIST OF SCHEMES

Scheme 1. Retrosynthetic analysis of sea lamprey pheromones ............................... 13
Scheme 2. Kallner’s allomerization of cholic acid to intermediate 1 ........................ 14
Scheme 3. Iida’s allomerization of cholic acid via bromoketone 6 ........................... 15
Scheme 4. Mclean’s allomerization towards the synthesis of petromyzonol PZ .......... 17
Scheme 5. Iida’s allomerization towards the synthesis of allocholic acid ACA ........... 19
Scheme 6. Mitra and Elliott’s single—step allomerization with Raney Ni ................... 20
Scheme 7. Proposed mechanism of allomerization with Raney Ni ........................... 23

Scheme 8. Single step allomerizations with dehydroxylated substrates at C7 position . . .24

Scheme 9. Preparation of substrate 12 for single step allomerization ........................ 26
Scheme 10. Allomerization of methyl cholate 12 with no. 4200 Raney Ni ................. 27
Scheme 11. Optimized conditions of allomerization with no. 2800 Raney Ni ............. 28
Scheme 12. Kinetic resolution of SIB/Son mixture ................................................. 33
Scheme 13. Dodson’s separation of SB/Sa mixtures ............................................ 33
Scheme 14. Resolution of SB/Sa mixtures via intramolecular acetal formation ........... 34

Scheme 15. Kinetic resolution of 2/1 (SB/5a) mixtures via selective acetal formation...35

Scheme 16. Stepwise allomerization sequences of cholic acid derivatives:

Oxidation at C3, dehydrogenation, and stereoselective reduction ............. 38
Scheme 17. Oxidation sequence of methyl cholate 12 at C3 position ....................... 39
Scheme 18. Selective C3 oxidation of methyl cholate with F etizon’s reagent ............. 40
Scheme 19. Zhou’s dehydrogenation with I( V) chemistry ..... i ................................ 41
Scheme 20. Hoye’s dehydrogenation with IBX toward the synthesis of PADS ............ 42
Scheme 21. Dehydrogenation of compound 2 into enones 10/ 13 with iodic acid ......... 43

Scheme 22.

Scheme 23.

OOOOOOOOOOOOOOO

Scheme 24.

Scheme 25.

Scheme 26.

Scheme 27.

Scheme 28.

Scheme 29.

Scheme 30.

Scheme 31.

Scheme 32.

Scheme 33.

Scheme 34.

Scheme 35.

Scheme 36.

Scheme 37.

Scheme 38.

Scheme 39.

Scheme 40.

Scheme 41.

Scheme 42.

Dehydrogenation of compound 41 into enone 42 with IBX .................... 44

Regioselective enolization of SB (A/B cis) 41 with IBX for enone formation
.............................................................................................. 45
Zhou’s stereoselective conjugate reduction with concomitant reduction of

ester to 50 (NB trans) 3-keto aldehyde ............................................ 46
Birch reduction of 4-en-3-one ester 42 ............................................. 48
Modiﬁed sequence of Birch reduction to convert 42 to 5d (A/B trans) l ...49
Yield of product 1 depending on the quenching time of Jones’ oxidation . . .50
Conjugate reduction of 4-en-3-one ester 42 by in-situ generated Smlz ....... 51
Stereoselective conjugate reduction of 4-en-3-one 51 with Na28204 ......... 52
Stereoselective conjugate reduction of 4-en-3-one 42 with Na2S204 ......... 53
Directed hydrogenation of 4-en-3-one 42 with Crabtree’s catalyst ............ 54
Stereoselective conjugate reduction of enone 42 with in-situ Cu—H .......... 56
Mclean’s stereoselective reduction of dienone 10 with Wilkinson’s catalyst57
Directed hydrogenation of enones 10/ 13 with Wilkinson’s catalyst .......... 57
Sames’ protocol of C-H activation (or internal hydride delivery), followed by
CC coupling ............................................................................. 58
Stereoselective reduction of enone 59 via internal hydride delivery .......... 59
Preparation of precursor enone 59 with benzyl protection ..................... 60
Stereoselective reduction of enone 59 via internal hydride delivery .......... 61
Synthesis of 3kACA via saponiﬁcation of 5a (A/B trans) compound 1 .....62
Synthesis of 3kPZS, potent male sea lamprey pheromone ..................... 64
Synthesis of larval sea lamprey pheromones, ACA and P28 .................. 65
Oishi’s allomerization with Myers protocol ....................................... 67

Scheme 43. Allomerization of enone 42 applying Oishi’s protocol .......................... 68

Scheme 44. Allomerization of enediketo compound 81/82 .................................... 70

xi

CHAPTER 1. INTRODUCTION

1.1. The Sea Lamprey in the Great Lakes

. .. . 1
Sea lamprey are among the most primitive vertebrates alive today. They

natively inhabit the Atlantic coast of North America and Europe, but can live in both

2 . . . . .
fresh and salt water. The screntiﬁc name for sea lamprey lS petromyzon marmus and it

is in the family petromyzontidae, the lamprey family.3 Its genus petromyzon is made up
of the Latin word ‘petra’ meaning ‘stone’ and the Greek word ‘myzon’ meaning ‘to
suckle’.3 The “stone sucker” is also their common name, which may have arisen from
the habit of males during spawning, when they create a depression in the river bed by
wriggling and removing stones with their mouth.4 Alternatively, sea lamprey are often
called cyclostome, which means “round mouth,” which refers to the fact that the lamprey

have a jawless and round-sucker type mouth.4

   

Figure 1. Sea lamprey, Petromyzon Marinus5

Sea lamprey resemble eel, which can cause confusion during identiﬁcation.

Unlike eel, however, sea lamprey have a dorsal ﬁn with a notch, and no pectoral or pelvic

ﬁns. as deplcted in Figure 1. Lamprey have a cartilaginous skeleton, which 1S another

characteristic of primitive species.3 Lamprey have gill openings consisting of 7 small
lateral clefts on the sides of the head and a single nostril on the upper surface of the

head.4 Lamprey commonly exhibit black or brown mottling on their backs, a metallic
violet color on the sides and a whitish gray on the belly.1 Average lamprey size is 12-20

inches in length and with a weight of 8-13 ounces.l A distinguishing characteristic is its
inferior, sucker type mouth ﬁlled with sharp teeth in concentric circles that surround a
ﬁle-like tongue (Figure 2).4 With this unique anatomy, sea lamprey are natively

equipped to attack and parasitize other ﬁsh. A lamprey uses its mouth to attach itself to a

ﬁsh, cut through the scales and skin, and feed on the host’s body ﬂuids, often scarring or

killing its prey.3 An anticoagulant in the lamprey’s saliva keeps the wound open for

. . 6
hours or even weeks so that the lamprey can continue to feed for prolonged periods.

Though the less than 1 pound itself, the lamprey is so destructive that it can potentially

kill six out of seven ﬁsh that it attacks, destroying as much as 40 pounds of ﬁsh or more

. . . 7
over its lifetime.

   

Figure 2. Sea lamprey jawless mouth8 and sea lampreys feeding on trout9

As mentioned above, the native range of sea lamprey in the North American

continent is the east coastal area in the Atlantic Ocean.2 However, lamprey have
expanded their range to include the Great Lakes, arriving through manmade locks and
shipping canals (Figure 3).10 The Welland Canal, which joins Lake Ontario to Lake Erie
bypassing Niagara Falls, was in place for nearly nine decades before sea lamprey invaded
Lake Erie.'0 Upgrades to the Welland Canal in 1919 appear to have provided an
improved avenue for sea lamprey to invade Lake Erie as they were found just two years
after improvements were made to the canal.10 Once lamprey were ﬁrst discovered in
Lake Erie in 1921, it took just 25 years for them to spread to the remaining Great Lakes:

Lake Huron in 1932, Lake Michigan in 1936, and Lake Superior in 1946.10

    

*0 r- j
y

1', Lake Superior ' “ . " '. .
iia' .. . l‘ \_ ‘ 7- \ w i I. .7 "' :3 .4;

_*’ _. . 4 Lake Huron ' ‘
>"_ . . | ‘ , 1*. Lake

       
  
  

."\
(.

 

'_._‘ -f ‘\

Ex, 1 , ' L V' i “ . .,._ i.
*—— . . - . 1 , .» , . ..
‘ - ., ’ 1’ ,A... - . ,
9 ., ' ,, a . Lake Erie Welland
" “ ‘7‘ ,. ,, .. ,f’,‘ ; — “i. _ , Canal
—— 7- ,__J l drainages with introductions 7 ' ‘ -. . ' . ' . nah

i: drainages in native range

 

Figure 3. Sea lamprey population in the United States” and in the Great Lakes12
Due to their intrinsic parasitic habits, sea lamprey are a serious problem for the
Great Lakes, devastating ﬁsheries, valued at about 1.6 billion dollars per year.2 Indeed,

the decline of several large native Great Lakes ﬁsh is mainly attributed to the introduction

of the sea lamprey. Lamprey have had the most devastating effect on a variety of cisco
species, lake trout, and walleye.lo At the height of the sea lamprey population, various

sport ﬁsh populations were suppressed which resulted in reduced recreational and

. . . . . 10 . . . .
commerc1al ﬁshing actiVities. Within ten years followmg the discovery of sea lamprey

in Lake Huron, the commercial lake trout ﬁshery fell from 3.4 million pounds to a ﬁshery

. 10 . .
not worth targeting. Furthermore, a large amount of money continues to be spent in

restoring the sport ﬁsh populations that have been damaged by sea lampreys.

1.2. Sea Lamprey Population Control in the Great Lakes
1.2.1. Current methods to control sea lamprey
In order to control the sea lamprey population in the Great Lakes, the federal

governments of the United States and Canada co-founded the Great Lakes Fisheries

Commission (GLFC) in 1956.2 Since its inception, the GLFC has actively sought
methods to eradicate or control the lamprey in the Great Lakes.2

Early methods included mechanical wires and electrical barriers.l3 Lamprey

barriers have been installed in a number of locations to block the migration of spawning
sea lampreys while allowing other ﬁsh to pass.

Another technique being used to reduce the sea lamprey

. . . . . l4 . .
population is the sterilization of males. During spawning runs,

male sea lampreys are collected, sterilized with a dose of bisazir Figure 4. Chemical
structure of bisazir

(P,P-bis(1-aziridinyl)-N—methylphosphinothioic amide,15 Figure 4) and released back

into the tributary. These sterile males compete with fertile males for spawning females.

This results in reduced fertilization of the eggs.

OH 0 N02
OH
N (1 :1 mixture)
H Cl
ogN
Cl HzN/VOH CF3

Bayluscide TFM
Figure 5. Chemical structures of lampricides
The application of selective lampricides is the primary method used at this time to
kill larval sea lamprey in the nursery streams. Chemical structures in Figure 5 represent
the two most common lampricides, Bayluscide (mixture of 5-chloro-N—(2-chloro—4-

nitrophenyl)-2-hydroxybenzamide and 2-aminoethanol) and TFM (3-trifluoro

methyl-4-nitrophenol). I 6

 

200

  
 

150 «

100 i

 

Population (thousands)

01
O

O . l _— Lake Trout
l -— Sea Lamprey

 

1930 1940 1950 1 960 1970 1980 1990

Year

Figure 6. Lake trout populations and sea lamprey populations in Lake Superior17

While sea lampreys will never be extirpated from the Great Lakes even with the

most aggressive combination of management approaches, the lamprey population can be

 

suppressed to a low level that will lessen the impact to the native ﬁsh. Figure 6
demonstrated the successful control of sea lamprey population in Lake Superior.18 The

population of lake trout seemed to be regulated by natural variation in early days. After
the ﬁrst emergence of sea lamprey in Lake Superior, the trout population dropped down
to almost nonexistent levels. Following the founding of the GLFC and application of
selective lampricides, mainly TFM, to eradicate sea lamprey, the lamprey population was
suppressed by as much as 90% since its population peak. This lowering of the lamprey
population was followed by a recovery of the trout population.

Although selective lampricide treatments have been successful at reducing
lamprey populations in the presence of native species of ﬁsh, this method has brought

about public apprehension. There were some reports about acute toxicity associated with

TFM, and its price has tripled over the past years.16 Moreover, the lampricides did not

show the same effectiveness in all the Great Lakes. For example, while they have

worked effectively in Lake Superior, lampricide use in Lake Huron, especially around the

. . . l9 . .
St. Marys River, has been met With only partial success. Ow1ng to these issues, the

GLFC decided in 2001 to reduce TFM usage by half and to pursue other management
strategies.
1.2.2. Life cycle of sea lamprey and related pheromones

After extensive sea lamprey studies, the GLFC developed several control methods
that are closely related to the life cycle of the sea lamprey.20 Each method mainly targets

lamprey in a speciﬁc stage: Barrier construction to block the spawning migration of adult

 

lampreys, sterilizing spermiating male sea lamprey, and the aforementioned application

of lampricides to decimate larval sea lamprey in the nursery streams

A closer look at the life cycle of the sea lamprey7’21 reveals that they hatch from

eggs located in tributaries during the spring and early summer. As larvae, the sea
lamprey lives in freshwater rivers and feed on microorganisms and detritus. The larvae,
which lack their oral disk, are swept downstream and burrow into the sand and silt, where
they remain for 3-15 years. During this time, the larval sea lamprey grows to a length of
approximately six inches.

At the end of the larval stage, the sea lamprey undergoes metamorphosis into an
adult lamprey, developing its oral disc and eyes. As an adult, the lamprey moves out into
the Atlantic Ocean, or in the case of the landlocked lamprey, it moves into the open water
of the Great Lakes, where it begins feeding on native ﬁsh for 12-20 months. It is only
during this stage that the sea lamprey poses a threat to other ﬁsh.

Once the parasitic stage ends, the sea lamprey becomes sexually mature, virtually
blind, and ceases feeding. They leave the Lakes and return to the tributaries where they
build nests and spawn. During spawning, there will be a large congregation of lampreys
all intertwined in a large ball. An average female spawns 60-70 thousand eggs. After
spawning the lamprey dies, thus competing the life cycle.

All these stages of sea lamprey life cycle are coordinated by several key

pheromones. Larval lampreys excrete migratory pheromones from gall bladders to attract

adult lampreys to their spawning region.22 Cued by these pheromones, adult lampreys

undertake nocturnal migrations into streams to spawn in the spring of their last year of

life. Migrating males typically arrive on the spawning grounds before females and

 

establish nests. During the ﬁnal stages of maturation (spermiation), male lampreys begin

to release sex pheromones that are highly attractive to ovulating females, signaling both

. . . - . 23
reproductive readiness and nest location to potential mates.

Recent investigations aimed at understanding the behavioral responses of
lampreys to these pheromones suggest that the pheromones could be used for potential
methods to control sea lamprey population in the Great Lakes.

1.2.3. Application of pheromones to sea lamprey control

As part of efforts to seek alternative ways to control sea lamprey in the Great
Lakes, pheromones as controlling agents have been investigated and are considered as the
most promising substitutes for lampricides.

In pursuit of such use, the Sorensen group at the University of Minnesota studied
migratory larval lamprey pheromones.22 They isolated and characterized several
components of the larval pheromone cocktail including allocholic acid ACA, and

petromyzonol sulfate PZS (Figure 7). Additionally, they have revealed that adult sea

lampreys show active migratory behavior in ﬂowing water treated with as low as

1040M concentration of ACA and P28 mixture.

 

allocholic acid, ACA petromyzonol sulfate, PZS
(3a,7a,12a-trihydr0xy- (3a,7a,12a,24-tetrahydroxy-
5a-cholan-24-oic acid) 5a-cholan-24-sulfate)

Figure 7. Chemical structures of migratory pheromones from larval sea lamprey

In 2002 and 2003, Weiming Li and co-workers at Michigan State University

identiﬁed two major components of male sea lamprey pheromones, 3-keto-allocholic acid
3kACA and 3-keto-petromyzonol sulfate 3kPZS (Figure 8).23 The Li group also
reported that the ovulating female lamprey responds to 3kACA and 3kPZS even at the

highly dilute concentrations of IOJOM and lO-IZM, respectively.

   

3-keto-allocholic acid, 3kACA 3-keto-petromyzonol sulfate, 3kPZS
(701,1 2a-dihydroxy- (701,1 2a,24-trihydroxy-
5a-cholan-3-one-24-oic acid) 5a-cholan-3-one-24-suIfate)

Figure 8. Chemical structures of sex pheromones from male sea lamprey

Pheromones that can induce spatial orientation are well known for insects, but not

23 . .
for vertebrates. Typically, sex pheromones in vertebrates tend to have a small range of
effectiveness, yet the sea lamprey’s pheromones can travel great distances. Data

. . . . 5 .
indicates that 3kPZS from male sea lamprey, for instance, IS 10 times stronger than sex

pheromone from female goldﬁsh in terms of effectiveness.23 In such a highly diluted

water stream, the virtually blind adult sea lampreys are guided to the speciﬁc spawning
area by their sensitive olfactory system. The Sorenson group has revealed that if the
nostrils of migratory adults are blocked, they fail to ﬁnd spawning streams. Studies on

the sense of smell of the sea lamprey have demonstrated that its reliance on this sensory

22
system may be greatest among ﬁsh.

The lamprey’s reliance on chemical communication may be exploited to the
future advantage. For example, these naturally occurring cues could be used to lure
lamprey into traps or into streams that are not suitable for reproduction. Thus, careful
application of migratory and sex pheromones may allow reduced use of lampricides
while still maintaining effective sea lamprey control. Indeed, the pheromone application
may become an environmentally friendly tool in the integrated management of sea
lamprey.

1.2.4. Isolation of sex pheromones for lamprey control agents

For the potential application of pheromones to sea lamprey control, the Li group
(Michigan State University) has mainly focused on sex pheromone components released
from male sea lamprey, especially 3kPZS which is one of the most potent components

showing 100 times stronger activity than other pheromones produced by sea lamprey.

The Li group isolated and identiﬁed sex pheromones from the following process.23

During the migration season of sea lamprey from May to July, adult sea lampreys were
collected from the ﬁeld. A spermiating male lamprey was held for 4 hours in 10 L of
lake water. Washing water containing sex pheromones was passed through ﬁltration
cartridges packed with C18 and then the C18 cartridges were extracted with methanol.
About 30 spermiating lamprey were treated by the same procedure. Finally, the mixture
of combined sex pheromones was subjected to prep HPLC to isolate two major fractions
of 30 mg and 2 mg. After spectroscopic data analysis and electro-olfactogram (EOG)
experiments, 3kPZS and 3kACA were structurally identiﬁed, respectively, as key
signaling components of male lamprey sex pheromone. These isolated pheromone

components can be potentially used as species-speciﬁc and environmentally benign

lO

 

control agents. More intriguingly, a report on capturing ovulating female sea lamprey in

pheromone-baited traps shed a promising light upon taking advantage of pheromones as a
. 24
method to control sea lamprey in the Great Lakes.

For the purpose of utilizing pheromones as selective lamprey control agents, a
continuous and economical supply of pheromones is required. The GLF C and its agents
have provided funding in search for environmentally friendly methods to control the
lamprey population and many research groups have been exploring efﬁcient ways of
isolation and synthesis of the pheromones. Due to laborious extraction and isolation
efforts with only small acquisitions of pheromones in vivo, various types of research to

synthesize these pheromones in vitro have been conducted by exploiting enzymology and

biosynthesis.25 Nevertheless, the only chemical approaches have been Dr. Mclean’s

synthesis of petromyzonol (P2) and Dr. lida’s synthesis of allocholic acid (ACA), vide
infra. For these reasons, chemical production of sea lamprey pheromones on large scale

would be valuable.

1.3. Retrosynthetic Analysis

Given the proposed use, the synthesis of pheromone control agents should be
inexpensive, practical and amenable to scale-up route. Furthermore, since the synthetic
products might be utilized in the Great Lakes, it is important for the synthetic approach to
be environmentally acceptable. A goal of this research is to help the environment, and as
such, great care must be taken to avoid introduction of toxic or harmful reagents, even at

low concentrations, into the lakes.

ll

Our synthetic approach to sea lamprey pheromones is presented in Scheme 1.
From the retrosynthetic point of view, all four major sea lamprey pheromones could be
transformed via relatively straightforward functional group manipulations from common
intermediate 1. For the practical preparation of the intermediate 1, cholic acid was
viewed as a plausible starting material because it is an inexpensive bile acid, bearing the
carbon skeleton and functional group precursors of the sea lamprey pheromones. In order
to achieve the successful conversion from cholic acid to intermediate 1, a crucial step of
the synthesis would be conversion of stereochemistry from 513 (A/B cis) to 501 (A/B

trans). In steroidal compounds, this type of epimerization to convert stereochemistry

from [3 to or speciﬁcally at the C5 position is called allomerization.26 Thus, the main

strategy and key step of the synthesis will be allomerization of this stereogenic center.

12

 

 

 

    

Ho” a 5 "'OH

H Cholic Acid

Scheme 1. Retrosynthetic analysis of sea lamprey pheromones

1.4. Prior Synthesis
As mentioned from retrosynthesis, the ring conversion of 513 stereochemistry of
cholic acid into 5a of common intermediate 1 is crucial for proper synthesis of all sea

lamprey pheromones. There are some literature reports of similar target syntheses

derived from cholic acid via allomerization.

l3

H 24 OH 24
CE) 3 002Me

 
 
 

 
  

 

 

 

1) MeOH, 1) KOH
3‘ H2804, rt MeOH, rt
HON H "'OH 2) (t-BuoiaAl O H "’OH 2) SeOZ (2.5 equiv)
h II Acld benzene/acetone 2 EtOH, reflux
C O c reflux, 18 h, 63% 4 h, 30%
24
002Me

 

4 (17%)

Scheme 2. Kallner’s allomerization of cholic acid to intermediate 1

In 1967, Kallner reported the ﬁrst allomerization of cholic acid to intermediate 1

’7
(Scheme 2)."7 Methylated cholic acid was selectively oxidized only at C3 position to

afford methyl 3-ketocholate 2 with Oppenauer’s reagent.28 To achieve allomerization,
they destroyed the 513 (A/B cis) stereochemistry initially to prepare or,[3-unsaturated
enone compound 3 by the action of Se02 in ethanol. Then, under the conditions of Birch

reduction, the stereochemistry of 5a (A/B trans) was exclusively installed on both
products 1 and 4. Although this protocol demonstrated the ﬁrst successful allomerization
of cholic acid, yields of the key steps were low, accompanied with signiﬁcant amount of

by-products, which have to be separated by column chromatography. In the

14

dehydrogenation step, they used stoichiometric amounts of SeOz, which is highly toxic

and expensive. Additionally, Birch reduction for stereoselective conjugate reduction
normally requires cryogenic and dry conditions, which along with the handling of liquid

ammonia can be problematic on kilo scale synthesis.

24 1) HCOZH (9. 5 equiv)
(302H HCIO4 (1.2 mol%)
50 °C, 1.5 h

quench with
Ac20 (6.7 equiv)
86%

 

HChol'c AC'd 2) NaOH (2 GQUIV)
acetone, rt, 0.5 h

 

 

 

 

1) Jones oxidation
1) semicarbazide (2.9 equiv) acetone, <10 °'C,
NaOAc (2.6 equiv) 0.5 h
HZO/ACOH two steps 92%
60 °C, 0.5 h -> rt, 1 h 2) Bra (2 equiv)
2) H20 & filtration p-TsOH (17 mol%)
suspended in AcOH DMF, rt, overnight
82%

3) pyruvic acid (20 equiv)
H20, ft, 1 day

 

 

 

 

 

  
 

1) Li, NH3(/). -78 °C

 

2) MeOH, H2304
0” rt, 57%
3

 
 

Scheme 3. Iida’s allomerization of cholic acid via bromoketone 6

15

In 1986, Iida group modiﬁed procedures for the enone formation without the

. 29 .
usage of selenium reagent (Scheme 3). Transformation to the (LB-unsaturated enone

was carried out by the sequence of oxidation at C3 to the ketone, then or-bromination,

followed by B-elimination. Tserng and Klein’s procedure for selective oxidation at C3
position was ﬁrst applied.30 Cholic acid was fully formylated on its three hydroxyl

groups, and then, mono deformylation at C3 position occurred with. The resulting free
hydroxyl compound 5 was oxidized with Jones’ reagent to the 3-keto compound in high
yield. In order to avoid the usage of selenium, the ketone precursor was activated by or-
bromination and then, the resulting bromo compound 6 was transformed into 4-en-3-one
7 via hydrolysis of semicarbazone intermediate. However, once compound 7 is formed,

the hydroxyl group at C7 position becomes extremely labile to both acidic and basic

. . 3| ,
conditions. For example, the presence of either a protected or free hydroxyl group at

C7 causes complications, mainly facile y,6-elimination to deliver 4,6-dien-3-one. Indeed,
Iida observed 17% of the eliminated material (8) in their allomerization. Finally,
selective 5a (A/B trans) stereochemistry of the crucial intermediate was installed by
Birch reduction due to the beneﬁts of ideal stereocontrol of cholic acid derivatives, even

with the aforementioned disadvantages of practicality of Birch reduction.

16

1) HCOgH (9.5 equiv)
H0104 (1.2 mol%)
40°C—»60°C,3h
quench with
A020 (6.7 equiv)

2) NaOH (2.1 equiv)
acetone ,.
0 °C -’ rt, 1 h HO‘

H
Cholic Acid 3) CH2N2
MeOH/EtZO, rt

   

Ph3P., ‘,PPh3
002Me ,Rh,
1) cat. PhSeSePh (25 mol%) Ph3P CI
m-iodoxybenzoic acid (4.1 equiv) Wilkinson cat. (50 mol%)
toluene, reflux, 18 h, 76% H2 gas

‘
V

2) Na2C03 (2 equiv)
MeOH, rt, 1 h, 100%

benzene/ethanol (1/1)
rt, 25 h, 50%

 

24
002MB

1) K-Selectride (2.9 equiv)
THF, -78 °C, 5 h, 95%

 

2) LiAlH4 (3.7 equiv)
THF, reﬂux, 13 h, 88% Petromyzonol PZ

 

Scheme 4. McLean’s allomerization towards the synthesis of petromyzonol P2

In 1987, the Mclean group investigated their own allomerization approach

towards the synthesis of petromyzonol (PZ), as illustrated in Scheme 4.32 Functionalized

cholic acid 9 was subjected to oxidation with catalytic amounts of selenium as developed

by the Barton group.33 The subsequent 1,4-dien-3-one 10 was reduced in the presence of

Wilkinson’s catalyst to afford complete stereoselection of 50. (A/B trans), presumably
from hydride delivery directed by catalyst complexation with the free 7a-hydroxyl group.
The ketone functionality at C3 of the desired 5a compound 1 was then reduced by a
bulky hydride source, potassium tri-sec-butyl-borohydride (K-selectride) to provide a

single diastereomer of 3a-hydroxyl compound in excellent yield. The last reduction of

17

the terminal ester completed the synthesis of petromyzonol PZ. This allomerization
procedure, however, is not without unattractive features. For the preparation of mono-
deformylated precursor 9, the methylation was carried out with diazomethane in order to
keep acid/base-labile formylated functional groups in tact. Diazomethane is problematic
at large-scale due to its hazardous and toxic nature. Secondly, while only catalytic
amounts of diphenyl diselenide were needed, to accomplish the one-step sequence of
oxidation and dehydrogenation to afford 1,4-dien-3-one 10, the selenium was relatively
high (25 mol%). Furthermore, the authors acknowledged that the reduction with
Wilkinson’s catalyst proved inconsistent and catalyst-batch-dependent. Moreover, the
reduction required 50 mol% loading of Wilkinson’s catalyst and provided only 50% yield
of product 1, along with observation of over-reduced alcohol at C3 position.

After 6 years, Iida group combined most of the advantageous methods in the

allomerization reports of cholic acid and established the most feasible route to the

synthesis of allocholic acid ACA to date (Scheme 5).34 A one-step oxidation and

dehydration procedure was chosen to afford a key intermediate 1,4-diene-3-one that was

. . ’5 .
ready for allomerization.J Precursor 9 was prepared by the sequence of methylation of

cholic acid, formylation, and selective deformylation at C3 position by
methanol/ammonia method. With this sequence, step of diazomethane usage was
eliminated. Alcohol compound 9 was converted to the 1,4-diene-3-one ll, catalyzed by
selenium reagent (27 mol%). Complete stereoselective reduction to So (A/B trans)
compound 1 was accomplished under Birch reduction conditions, which were found to be
preferable to hydrogenation by Wilkinson’s catalyst. Again though, the selenium loading

was still high and the same concerns over the Birch reduction on large scale remain.

18

1) MeOH, H2804, rt
4 2) HCOQH (9.5 equiv)
CQZH HCIO4 (1.2 mol%)
50 °C, 1.5 h

quench with

, A020 (6.7 equiv) \
"0H 86% Ho“
H Chollc Acid 3) MeOH/NHa- '1

0.5 h, quant. yield

      

1) cat. (PhSeO)20 (27 mol%)
CBH5102 (4.1 BCIUlV)
toluene, reflux, 3 h, 70%

1) Li/NH3/NH4CI
-78 °C, 20 min

ll
11

2) H2804, MeOH
65%

2) excess LiOH
MeOH, TI, 1 h, 95°/o

 

24
002MB

1) K-Selectride (2.9 equiv)
THF, ~20 °'C, 3 h, 88%

 

2) KOH, quant. yield

   

Scheme 5. Iida’s allomerization towards the synthesis of allocholic acid ACA

As discussed above, most allomerizations of cholic acid derivatives were carried
out via the stepwise sequence of oxidation at C3 and (LB-unsaturated ketone formation,
followed by stereoselective reduction to convert stereochemistry from 513 to 501. While
new pathways for allomerization have developed and great achievement has been made,
the preparation of precursors for allomerization still requires several steps of functional
group manipulation. Also, due to various safety and cost issues, none of the
allomerization procedures are ideal for an environmentally friendly pest management

program in economical way.

19

24
002MB

W-2 Raney Ni 250 wt%
p-cymene

 

reflux H
10 h 1 (12-14%)

 

Scheme 6. Mitra and Elliott’s single-step allomerization with Raney Ni

Interestingly, back in 1968, Mitra and Elliott demonstrated transformation of

methyl cholate 12 to desired intermediate 1 via single-step allomerization (Scheme 6).35

By the action of Raney Ni in boiling p-cymene discovered by Chakravarti group,37 513

(A/B cis) stereochemistry of methyl cholate 12 was smoothly converted into 501 (A/B
trans), along with concomitant selective oxidation at C3 position in one step. This
method is attractive superﬁcially but there are some drawbacks. Although it is single
step allomerization, yield of desired product 1 was low (12-14%) and crude reaction
mixture included series of by-products in considerable amounts of each. Moreover, all
compounds in the mixture are accompanied by their corresponding 58 isomers and the
puriﬁcation or separation of the 501 compounds from the 58 compounds was not

practical. Indeed, the Iida group noted that Raney Ni reactions were erratic and resulted

. . . . . . . . 38
in complex mixtures, which requrred extensrve laborious chromatographic separation.

Despite such results and Iida’s comment, the Raney Ni reaction is still a single
step allomerization, cutting out many steps and the need for expensive and/or toxic
reagents. We hypothesized that with the development of practical methods for separation
and improved reaction conditions, this single step allomerization would be potent method

and thus worth further investigating. Therefore, our ﬁrst approach to 3kPZS and analogs

20

commenced with an investigation of the single step allomerization mediated by Raney Ni.

21

CHAPTER 2. SINGLE STEP ALLOMERIZATION WITH RANEY NICKEL

2.1. Mitra and Elliot’s Allomerization with Raney Ni
2.1.1. Single step allomerization of methyl cholate

In order to be utilized as sea lamprey population control agents in the Great
Lakes, chemical synthesis of pheromone components needs to be practical and

environmentally benign. Among the literature reports that seemed to suit these
. . . . . . . 36
requirements. the allomerization With Raney Ni reported by Mitra and Elliot stands out.

Action of Raney Ni in boiling p-cymene smoothly transformed methyl cholate 12 into
product 1 (Scheme 6). Other reports about allomerization of cholic acid incorporated the
stepwise sequence of oxidation at C3 position, dehydrogenation to or,B-unsaturated
ketone, and selective reduction, in order to achieve conversion of stereochemistry from
58 (A/B cis) to 501 (NE trans). Since cholic acid bears three hydroxyl groups at C3, C7,
and C12 positions, these multi step approaches needed to be accompanied by selective
protecting group manipulation. In contrast, Mitra and Elliot’s allomerization converted
stereochemistry from 58 (A/B cis) of methyl cholate 12 to Sc (A/B trans) of desired
product 1 in a single step along with selective oxidation at C3 position without any need
of functional group protection. Empirically, this procedure is a one-step allomerization,
but reaction actually proceeds via a series of stepwise allomerizations.

2.1.2. Mechanism of allomerization with Raney Ni

In their early reports, Mitra and Elliot presented their mechanism of the

all omerization with Raney Ni (Scheme 7).39 Raney Ni was said to oxidatively add into

22

the O-H bond of the sterically more accessible 3a-hydroxyl group, followed by B-hydride
elimination to afford 3-keto compound 2. Selectively oxidized keto compound 2 enolizes
toward at C4 and Raney Ni promotes B-hydride elimination affords mil-unsaturated
ketone 13. Lastly, the resulting enone compound 13 is reduced to provide desired

product 1 with 501 (A/B trans) stereochemistry.

24
002Me
W-2 Raney Ni 250 wt%

pcymene

reflux
10 h

24
COQMG

 

Scheme 7. Proposed mechanism of allomerization with Raney Ni
After chromatographic separation of the reaction mixture on alumina, Mitra and

Elliot isolated three major fractions, desired product 1 (12-l4%), over-oxidized product

14 (IS-20%), and dehydroxylated product 15 (20-22%) as shown in Figure 9.36b While

all these products have 501 (A/B trans) stereochemistry, each product was accompanied
with the corresponding 58 (A/B cis) isomer prior to another puriﬁcation by preparative

layer chromatography (plc), followed by recrystallization.

23

      

H “'0” H
1 (12-14%) 14 (13-20%) 15 (20-22%)

Figure 9. Identiﬁed products from allomerization of methyl cholate by Raney Ni
Compound 14 was possibly the result of over-oxidation of the desired product 1 at
C7 by Raney Ni. Dehydroxylated compound 15 is also produced via proposed
intermediate 13. Here, once the 0i,B-unsaturated ketone is set up, the hydroxyl group at
C7 becomes easily eliminated to provide 4,6-dien-3-one compound, which is then

probably reduced by Raney Ni to afford dehydroxylated product 15.

 

   

24
C02Me
W-2 Raney Ni 250 wt%
p-cymene
reflux ' O
H 16:R=H 10h H 18:R=H(70%)
17: Ft = OH 19: R = OH (60%)

   

H 20: R = H (20%) 22: n = H (10%)
21: Ft = OH (20%) 23: n = OH (8%)

Scheme 8. Single step allomerizations with dehydroxylated substrates at C7 position

Later, Mitra and Elliot investigated the mechanism of allomerization of substrates

without 7a-hydroxyl group under the same condition of Raney Ni (Scheme 8).39

24

Allomerization of substrates l6 and 17 provided three isolated products, of which the
formations were mechanistically examined. Isolation of enone compounds 22 and 23
clearly demonstrated that allomerization by Raney Ni proceeds via the sequence of
oxidation, dehydrogenation, and reduction. Moreover, when each isolated product was
subjected to the Raney Ni conditions, very similar results were obtained. For instance,
the subjection of 18 under the condition of Raney Ni gave three compounds, 18 (70%),
20 (20%). and 22 (10%) probably after reaching equilibrium. The same equilibrium was
established with either compound 20 or 22, affording the same ratios of three products.
These data supported the hypothesis that the three products are in equilibrium during the

process.

. . . . . . 39
Mitra and Elliot also looked into the role of solvent in these allomerizations.

The net reaction is one of epimerization at C5 from 513 (A/B trans) to 50 (NB cis) along
with selective oxidation at C3. Therefore, the overall reaction is an oxidation, where the
starting material loses two hydrogens in the course of the reaction. From labeling studies,
Mitra and Elliot found that tritium at C4 of the steroidal compounds was transferred to
solvent by way of hydrogenolysis or reduction through the action of Raney Ni. Thus,
p-cymene, is working as solvent as well as hydrogen acceptor.

This reaction has advantages as a one-pot allomerization, but there are some
drawbacks. Allomerization of methyl cholate 12 provided mixtures of desired product 1,
over-oxidized product 14, and dehydroxylated product 15. Compound 15 is especially
problematic as it would be a dead-end because its transformation back into product 1
would not be straightforward. Furthermore, each product contained the corresponding 58

(AJB cis) isomer prior to additional puriﬁcation. On the plus side, compound 2, one of

25

the SB isomers, could be recyclable into product 1 through the equilibrium process.
Perhaps the biggest operational issue is that puriﬁcation or separation of 513/501 mixture
requires undue effort. Despite of these issues, this reaction is a single step
allomerization, cutting out many steps. Thus, it is still attractive and worth further

investigation.

2.2. Optimization of Single Step Allomerization with Raney Ni

As discussed above, we need to resolve those several negative issues surrounding
the single step allomerization with Raney Ni. Obviously, the yield of desired product 1
needs to be improved. Thus, production of dead-end by-products l4 and 15 should be
minimized. In tandem with this aim, we need to improve the ease with which the 58 and
501 mixture is puriﬁed.

We began by exploring the allomerization of methyl cholate 12 with Raney Ni.
Substrate 12 was prepared from commercially available cholic acid. Cholic acid was
methylated ﬁrst in methanol, mediated by 2 equivalents of trimethylsilyl chloride,
TMSCI (Scheme 9). This methylation seemed suitable for large-scale synthesis because
the reaction proceeded smoothly at room temperature and open-to-air. Concentration of
the resulting crude reaction mixture induced the slow formation of colorless needles of
methyl cholate 12 in excellent yield.

QH 24

    

TMSCI (2.0 equiv)

‘
*7

"’OH MeOH (0.25M) Ho”
Cholic Acld rt. overnight, >97%

 

Scheme 9. Preparation of substrate 12 for single step allomerization

26

Mitra and Elliot performed the allomerization of methyl cholate with freshly

prepared W-2 Raney Ni. This Raney Ni was prepared by the treatment of sodium

hydroxide on Raney catalyst powder (no. 2813) according to Mozingo’s method.40

However, the same Raney catalyst powder is no longer available, so we used
commercially available Raney Ni powder that was washed right before the reaction.

Allomerization of methyl cholate 12 was thus initiated with Raney Ni (no. 4200) in p-

cymene (Scheme 10).

24
002MB

 
  
 

no.4200 Raney Ni 250 wt%
pcymene (0.19M)

ll

 

"’OH reflux
H H
12 10 h 2 (56, 16%)
(23.7 mmol) 2/1 (sis/sci = 2/1, 15%)

Scheme 10. Allomerization of methyl cholate 12 with no. 4200 Raney Ni
The reaction mixture was mechanically stirred at reﬂux for 10 hours, yielding
complicated crude mixtures. After separation on 12% deactivated neutral alumina, 10%
of starting material 12 remained, and oxidized product 2 (58, NB cis) was obtained in
16% yield. More importantly, the desired product 1 (50, NB trans) was obtained as a
mixture of 2 (58, A/B cis) and 1 (501, A/B trans) with a ratio of about 2 to l favoring
compound 2. The combined yield was 15%. Additionally, there were several
unidentiﬁed compounds including UV active compounds that were present in signiﬁcant
amounts. Initial attempts at a single step allomerization with no. 4200 Raney Ni did not

give us any more promising results.

27

We worked on optimizing this reaction by screening different Raney Ni catalyst
and changing catalyst loading, solvents, concentrations, and reaction times. Under lower
V catalyst loading and higher concentrations, formation of oxidized product 2 (58, NB cis)
increased up to 50% yield, but there was no considerable change in the calculated yield of
desired product 1 (501, A/B trans). One hour of reaction gave us complicated mixtures
including desired product 1. As the reaction was run for longer time, the complicated
reaction mixtures got simpliﬁed on TLC but there was no change in amount of product 1.
The type of Raney Ni emerged as a key factor in the efﬁciency in which desired product
1 was formed. Scheme 11 represents our optimized results of the allomerization of

methyl cholate 12.

  
 

no.2800 Raney Ni 230 wt%
p-cymene (0.19M)

ll

 

HO‘" ”OH reflux H
12 10 h 2 (5B. 43%)
(2.37 mmol) 2/1 (56/501 = 1/1, 25%)

Scheme 11. Optimized conditions of allomerization with no. 2800 Raney Ni

Starting material 12 was recovered in 5-10% yield, so the reaction did not go to
completion. Yields of the by-products were greatly reduced and the only two major
products were 2 (58, A/B cis) and 1 (501, A/B trans). We isolated 43% of oxidized
product 2 (58, A/B cis), which could be recyclable to desired product 1 (501, A/B trans)
through an equilibrium process. A l to 1 ratio of 58/50 mixture was obtained in 25%
yield. Finally, separation of the mixture on neutral alumina provided us a small amount
(1% yield) of the desired product 1 (501, A/B trans). Stereochemistry of compounds 2

and 1 was conﬁrmed by X-ray crystallography, which was obtained by Dr. Feng Shi

28

(Figure 10). Additionally, we isolated a trace amount of enone 13, which indicates the

presence of equilibrium in this reaction.

24
COQCH3

VS.

   

3 . O O 1 (50:, NB trans)
O 58 (A/B crs) ester 2 mono-protected with

4-nitio-benzoyl
group at 7a—OH

Figure 10. Three-dimensional structures of 58 (A/B cis) ester 2 and
derivatized 5(1 (A/B trans) ester 1 based on their X-ray crystal structures

We considered this single step allomerization processes to be slightly improved
over the original protocol. By utilizing commercially available Raney Ni, the amount of
by-products was considerably reduced while the overall yield of usable products
increased. By usable we mean, products that are desired or can be converted into the
desired compound signiﬁcantly were able to effect the conversion of 2 (58, NB cis) into
1 (501, A/B trans). Therefore, we next looked into the reversibility of this reaction.

After subjection of compound 2 (58, A/B cis) to the same Raney Ni conditions, a
l to 1 ratio of 58/50 mixture was obtained. Also, we subjected the mixtures of 2/1
(58/501=1/ 1) to the same conditions, but this gave no change in the mixture ratio. On the
other hand, subjection of compound 1 (501, A/B trans) in a small scale (10 mg, 0.0237
mmol) to the same conditions provided us degradation of compound 1, not equilibration
due to the stirring issue of paramagnetic nature of Raney Ni with magnetic bar, which
should be performed in a dilute concentration with mechanical stirrer or large scale of
reaction. From these equilibrium experiments, we knew it was possible to increase the

overall yield of desired product I (501, A/B trans). Nevertheless, we still had an

29

 

 

 

111
t,-

abundance of the 58/501 mixture, so we needed to work on the development of a practical
separation protocol.

2.3. Separation of Mixture of 58 (A/B cis) 2 and 50 (AIR trans) 1

2.3.1. Separation by liquid chromatography on neutral alumina

Initially, we followed Mitra and Elliot’s separation method.36 They separated
their crude mixture on 12% deactivated neutral alumina to afford three major fractions.
The corresponding 58 (A/B cis) isomer of each fraction was removed by preparative
liquid chromatography (plc) and separated 501 (A/B trans) isomers were puriﬁed by
crystallization.

In our work, we examined several deactivation levels (0%, 3%, 8%, and 12%) of
neutral alumina. Contrary to Mitra and Elliot’s results, in our hands, liquid
chromatography on 3% deactivated neutral alumina gave us pure 501 (A/B trans) product
1 without need for a further puriﬁcation step, however only small amounts of l were
isolated. As a result, separation by liquid chromatography required multiple runs and it
would be impractical for large-scale synthesis.

2.3.2. HPLC separation of mixture of 58/5a carboxylic acids at C24

While we were working on analysis and separation of 58/501 mixtures, interesting
results were observed. Under the reverse phase of HPLC condition, we could separate 58
(A/B cis) and 501 (A/B trans) mixtures, but those compounds were carboxylic acids after
hydrolysis of methyl ester mixtures at C24 (Figure 11). On the other hand, with
58/501 methyl ester mixtures, only 58 (NB cis) ester 2 eluted. The 501 (A/B trans) ester 1
was never detected under various HPLC conditions. We hypothesize that there might be

a selective interaction between 501 (A/B trans) ester 1 and the solid support of the normal

30

phase of HPLC columns. The selectivity might originate from the structural difference

between 58 (A/B cis) ester 2 and 501 (MB trans) ester 1.

 

 

 

 

 

 

o 20 40 60 80
Retention Time

HPLC condition: prep Nova-Pak HFl, C18 3.9X300mm, waters, AB = 72/28,
eluent A =0.01%TFA, eluent B = 70%ACN/0.01%TFA, rate = 0.5 mL/min.

Figure 11. Separation of mixture of 58/501 carboxylic acids at C24 on HPLC

Based on three-dimensional structures of each compound shown in Figure 12, the
701-hydroxyl group seems to be the most sterically differentiated functional group
between 58 (A/B cis) ester 2 and 501 (A/B trans) ester 1. In an intermolecular interaction,
the more sterically hindered 701-hydroxyl group on 58 (A/B cis) ester 2 would likely react
Slower than the 7o1-hydroxyl group on 501 (A/B trans) ester 1. For this reason, the 701-
hydroxyl group on 501 (A/B trans) ester 1 might interact selectively with the polar
functional groups of the solid support in a normal phase of HPLC columns. In contrast,

the selective intramolecular reaction of 58 (A/B cis) ester 2 could be induced from the

31

close proximity between the 3-keto functionality and the 701-hydroxyl group. If we could
utilize the reactivity difference between 58 (A/B cis) ester 2 and 501 (A/B trans) ester 1,

an easy and practical way of separation might be achieved.

VS.

    

OH
3 58 (A/B cis) ester 2 501 (A/B trans) ester 1

   

OH

Figure 12. Three-dimensional structures of 58 ester 2 and 501 ester 1
2.3.3. Kinetic resolution of 2/1 (SB/5a) mixtures
In order to induce selective reactivity between 58 (A/B cis) ester 2 and 501 (A/B
trans) ester 1, we probed their intermolecular reactivity. If the hydroxyl group at C7
could be mono-protected or two hydroxyl groups at C7 and C12 could be tethered with a
proper linker, the sterically more accessible 7o1-hydroxyl group of 501 (A/B trans) ester 1
might react faster than that of 58 (A/B cis) ester 2. Such a kinetic resolution was tried

with benzoyl mono-protection of the hydroxyl group at C7 and with boronic ester

tethering of the two hydroxyl groups at C7 and C124] (Scheme 12).

32

002MB

 

p-nitrobenzoic acid (0.6 equiv)
DMAP (0.1 equiv)

 

4: complicated mixture
DCC (0.6 equiv)
CHZClz, rt

002Me

B(OMe)3 (0.6 equiv)

 

> complicated mixture
THF, 0 °C

(515/50 : 1“)

Scheme 12. Kinetic resolution of 58/501 mixture

Unfortunately, both of these reactions provided us complicated mixtures. No

separation of the 58/501 mixtures via either mono-protection, bis-protection, or

9 9
H H
l ——-——>
5 OH k536
O 3 OH

oligomerization, etc were achieved.

 

 

 

 

O .
1. 26 (58, A/B 013) A 28 (58, NB cis)
68%
9 Pd/C
H2 MeOH
H0 g + cat.p—TsOH
O 3 4 25 MeOH, rt "
9 9
H
¢3 51 ' kl; c')
O H OH 3
27 (501, A/B trans) OCH3
10% 29 (58, A/B cis)
quant. yield

Scheme 13. Dodson’s separation of 58/501 mixtures
Then, we turned our attention to selective intramolecular interactions. From the

literature, we found excellent separation of 58/501 mixtures reported by Dodson group

33

(Scheme 13).42 Under hydrogenation conditions, 4-en—3-one 25 was reduced to mixtures

of their 58/501 isomers. From the mixture, 58 (A/B cis) compound 26 was selectively
transformed into hemiacetal 28 as a result of the close interaction between the 3-keto
functionality and the 901-hydroxyl group, while the reduced 501 (A/B trans) compound 27
remained unchanged. After reaction was done, several subsequent crystallizations of the
residue provided the isolation of 28 (58) and 27 (501) easily and in a practical way.
Following the lead provided by this example, we tried to selectively form the acetal of a
2/1 (58/501) mixture, realizing though that the reacting hydroxyl group of 2 (58, A/B cis)
was positioned at C7, not C9 (Scheme 14) and would this make the desired reaction more

formidable.

002MB

p-TsOH (1.1 equiv)

  

 

> no reaction

 

"'OH MeOH, 11

H 2/1 (56/561 =1/1)
Scheme 14. Resolution of 58/501 mixtures via intramolecular acetal formation
Under acidic conditions in methanol, the intramolecular acetal formation was
attempted as a means to resolve the 58/501 mixture. Unfortunately, the reaction did not
Occur and all of the 58/501 material was recovered. As suggested, this result might be
Caused by the distance between the 3-keto functionality and the 701-hydroxyl group of 58
(A/B cis) compound 2. Comparison of Newman projections of the two 58 (A/B cis)
Substrates, 26 and 2 (Figure 13) shows that the 901-hydroxyl group of 26 is close enough
to form hemiacetal 28 or acetal 29 with 3-keto functionality, but the 701-hydroxyl group

0f 2 is sufficiently far from the 3-keto functionality to impede acetal formation.

34

VS.

   

O 26(58,A/B cis) O 2(58,A/B cis)

Figure 13. Newman projections of two 58 (A/B cis) compounds, 26 and 2

Additionally, we attempted to utilize the 3-keto functionality for the resolution of
the 2/1 (58/501) mixtures. With acetal formation at the 3-ketone (Scheme 15), we
expected faster reaction from the 501 (A/B trans) compound 1 over the 58 (A/B trans)
compound 2 because the 3-keto functionality of the 501 (A/B trans) compound 1 is less

sterically hindered. In monitoring the reaction by NMR, several aliquots were taken out

of the mixture. Each aliquot was treated with NaBH4 to remove remaining ketone. After

separation of acetals and reduced alcohols, ratios of the acetal were checked by lH-NMR.
As a result, forming acetals of all aliquots demonstrated the same ratios of l to 1 (58/501).

With these unsatisfactory resolution results, we looked into other separation conditions.

COQMG

CUClz'ZHgO (0.1 SQUIV)

 

glycol/dioxane (1 /1)
80 °C

   

2/1 5 /50.=1/1 -_
( P ) 30/31 (58/501 1/1)

no resolution (0.5h, 1h, 2h, 4h, 8h)

Scheme 15. Kinetic resolution of 2/1 (58/501) mixtures via selective acetal formation

35

2.3.4. Separation of 2/1 (58/501) mixtures by gas chromatography

Figure 14 is gas chromatography (GC) traces of mixtures of 2 (58) and 1 (501).
The molecular weight of these esters is 420.58, so it needed the harsh conditions of GC as
indicated in the legend of Figure 14. While we ﬁnally observed the resolution of the 2/1

(58/501) ester mixtures, prep GC would not be practical during large-scale synthesis.

mVolts
(it
1.5 j
1.0 i

0.5

0.0 .L

mVolts

 

‘- 43:) 87.310
r

 

K

1.5 1
1.0

0.5 7; ’
l 0 ’0H

0.0 \x H 2/1 (513/50 = 3/1)

  

82 207

 

 

 

 

 

mVolts
1.5 if g
, (\i
1.0 1‘ co
1‘
05 ‘ ’I [Ii
' w H 2 (58, A/B cis) i l
0.0 4; J p__
10 20 30 40 50 60 70 80
minutes

GC conditions: Factor FourTM: Capillary Column VF-1ms, 15m 0.25mm 0.25pm, Varian
flow rate = 65.5 mL/min, oven temp 230 °C, injector temp 250 °C, FID temp 250 °C

Figure 14. Separation of 2/1 (58/501) mixtures by gas chromatography

36

2.3.5. Resolution attempt of 58/5a mixtures via sublimation

While preparative GC would not suit our needs, discussions with Professor Adam
Matzger of the University of Michigan suggested that sublimation under high vacuum
might be viable. As such we tested a couple of derivatives of our 58/501 mixtures (Figure
15) under such conditions. The Matzger group attempted sublimation with 58/501
mixture of acetyl derivatives 32/33, and we independently tried sublimation of both ester
58/501 mixtures under the high vacuum of a silicon oil pump. However, none of these

attempts provided us practical separations of the 58/501 mixtures.

       

o
"0Ac (’0 H "'OH
32/33 (56/50. = 3/1) 30/31 (56/501 = 1/1)

no sublimation, melt no sublimation

Figure 15. Sublimation attempt to separate 58/501 mixtures

In the end, while we improved some conditions of a single step allomerization
with Raney Ni to increase overall yield of potential materials and minimize dead-end by-
products. Recently, from our extensive search for separation of 58/501 mixtures,

scrupulous and multiple column chromatography on silica gel (hexane:acetone=2/l) gave

. . 43 . .
us clear separation of 58/501 (1/1) mixtures. However, there was still the issue of

impractical separations of the 58/501 mixtures. This unresolved issue of separation led us

to a full investigation of stepwise allomerizations.

37

CHAPTER 3. STEPWISE ALLOMERIZATION

As discussed earlier in Chapter 1, stepwise allomerization was generally achieved
via the following sequences: Oxidation at C3, dehydrogenation and stereoselective

conjugate reduction (Scheme 16). We explored oxidation at C3 of cholic acid derivatives

   

 

 

ﬁrst.
OH 24
E COQR
Single-Step Allomerization
OH
HO H
t
Oxidatlon Stereoselective
at 03 : Reduction

‘-—---—

 

Scheme 16. Stepwise allomerization sequences of cholic acid derivatives:

Oxidation at C3, dehydrogenation, and stereoselective reduction

3.1. Oxidation at C3 Position of Cholic Acid Derivatives

Since cholic acid has three hydroxyl groups at C3, C7, and C12, the challenge is
to oxidize only the 301-hydroxyl group with the other hydroxyl groups at C7 and C12
remaining intact. For this selective oxidation at C3, all three hydroxyl groups can be

protected ﬁrst, and then the hydroxyl group at C3 can be selectively deprotected,

38

followed by oxidation of the resulting 301-hydroxyl group (see section 1.4).29’30’34"5

Following this sequence, the 3o1-hydroxyl group of methyl cholate 12 was selectively

oxidized (Scheme 17).44

 

   

24
COQMG
AcCl
rt, 5.5 h, 93% T
K2003 (2 GQUIV)
MeOH
rt, 2 h, 90%

24
002MB

SiOQ-PCC (2 equiv)

 

CHchZ \“
1'1, 30 min, 90% HO

   

Scheme 17. Oxidation sequence of methyl cholate 12 at C3 position
Neat reaction of methyl cholate 12 in acetyl chloride proceeded at room
temperature to provide tri-acetylated product 34 in 93% yield after recrystallization.
Selective deacetylation at C3 of compound 34 was efﬁciently performed with treatment

of potassium carbonate in methanol. After recrystallization, selectively deprotected 35

was obtained in good yield. Lastly, a 1:1 mixture of SiOz and PCC rapidly oxidized the

free hydroxyl group of compound 35 to ketone 32 in high yield. We embraced this
protection/deprotection sequence for the oxidation of the 301-OH because product
puriﬁcation does not require chromatographic separation as recrystallization of the crude
reaction mixture provides pure material in excellent yields. Furthermore, the toxicity of

chromium reagent is manageable in its solid supported form. Indeed, oxidation of

39

compound 35 with this PCC reagent has a potential for scalability, given its ease of work-

up.

This oxidation sequence could also be improved by application of Tsemg’s

method.45 In 1978, Tserng reported that treatment of methyl cholate with Fetizon’s

reagentd'6 could selectively oxidize 3o1-hydroxyl group without the need for protection of

the other hydroxyl groups at C7 and C12. In order for oxidation to take place, both the

hydroxyl group and the hydrogen on carbon should be attached to the surface of the

AgCO; on celite.45 Therefore, in this case, the structurally more accessible 3o1-hydroxyl

group and 38-hydrogen are selectively absorbed on the surface of the oxidizing reagent to

produce the 3-keto compound 2.45

24
COZMG

 
  

AgQCO3/Celite (2.0 equiv)

 

l

toluene
HO OH reflux, 8 h

12 75-85%

 

Scheme 18. Selective C3 oxidation of methyl cholate with F etizon’s reagent

We carried out the same oxidation protocol of oxidation with methyl cholate 12
(Scheme 18). Methyl cholate 12 was reﬂuxed in toluene with freshly prepared Fetizon’s
reagent. In the course of the reaction, water was removed by a Dean-Stark apparatus.
Upon completion of the reaction, as monitored by TLC, the oxidizing reagent was ﬁltered
off and the ﬁltrate was concentrated to afford crystalline product 2 in good yield. This
method proved very efﬁcient and is likely applicable to large-scale synthesis. Moreover,

once the oxidation is complete, we would have several choices of alcohol protecting

groups, should the C7 and C12 hydroxyls need protection during later transformation.
With the 3-keto compounds in hand, we turned to the next step, dehydrogenation to the

enone.

3.2. Dehydrogenation with I(V) Reagents
As shown in Chapter 1 (see section 1.4), the unsaturated 4-en-3-one compounds

have been prepared by o-halogenation of the 3-keto compounds, followed by 8-

27,32,34

. . . 39 . . . . .
elimination or selenium catalyzed direct oxidation/dehydrogenation of 301-

hydroxyl compounds. However, those methods were not ideal for a large-scale synthesis
due to various safety and cost issues of reagents.

24
C02M6

 
  
 

   

R = H: Hl03 (1.2 equiv), DMSO
40-50 °C, 11 h, 61%

 

   

0 "'on a = MOM: 13x (2 equiv). DMSO 0

"'on
H TFA (30 mol%)
R: H 36 ,, R: H 33 CH3OCHQOCH3
R=MOM 37 rt. 24 “1 87 /° R=MOM 39 P205,CHC13
rt, 5h, 33%
Li/NH3(I)
O -73°C
NH3 73%

 

    

 

 

”OMOM
squalamine

 

Scheme 19. Zhou’s dehydrogenation with I(V) chemistry

toward the synthesis of squalamine

41

In 2003, the Zhou group reported iodine (V) chemistry dehydrogenations

(Scheme 19).47 Modifying Nicolaou’s protocol of iodine chemistry,48 they utilized iodic

acid or acid catalyzed o-iodoxybenzoic acid (IBX) in DMSO to convert 58 (NB cis) 3-
keto compounds into 4-en-3-one compounds. Furthermore, MOM protected enone
compound 39 was allomerized by the Birch reduction conditions to afford 501 (A/B trans)
compound 40 along with concomitant ester reduction to the aldehyde at C24. Then, they
took substrate 40 onto their synthesis of squalamine. Two years later, Hoye and co-

workers applied the Zhou’s IBX protocol to the synthesis of petromyzonamine disulfate,

PADS (Scheme 20).49

24
COzMe

IBX (2 equiv)
TFA (30 mol%)

DMSO, rt, 24 h, 87%

   

Li/NH3(/)
-73 °c
73%

 

 

 

   

PADS

Scheme 20. Hoye’s dehydrogenation with IBX toward the synthesis of PADS
We decided to examine this iodic acid chemistry because it is nontoxic and an

inexpensive reagent. Also, alcohols are known to be inert to this oxidant, thus no

. . 4 ,4 . . .
protection of hydroxyl groups 15 needed. 7 8 Lastly, substrate 36 1S structurally Similar

42

to our methyl 3-ketocholate 2. Hence, we carried out the dehydrogenation of compound
2 with iodic acid, as illustrated in Scheme 21. A solution of substrate 2 with iodic acid
and cyclohexene in DMSO was stirred in a sealed tube at 45-50 °C for 1.5 day with light
excluded. After chromatographic separation, we obtained 1 to 1 mixture of 1,4-dien-3-

one 10 and 4-en-3-one 13 in combined yield of 35-43%.

H103 (2 equiv)
cyclohexene

    

DMSO, 45-50 °C
H with light excluded ,1 4114/ 4 = 1,1
2 1.5 CI, 35-43% 10 31 A )

Scheme 21. Dehydrogenation of compound 2 into enones 10/13 with iodic acid

Although a one-pot dehydrogenation was achieved with iodic acid, the reaction
proved to be a bit complicated. The reaction provided a complex mixture and the isolated
products 10 and 13 were not high yielded. Furthermore, the mixture of 10 and 13 was
not separable in our hands. Thus, we turned our attention to other iodine chemistry with
IBX.

Scheme 22 shows the dehydrogenation of compound 2 to afford 4-en-3-one
compound 42. Since IBX can oxidize alcohols, the two hydroxyl groups at C7 and C12
need to be protected. Thus, a solution of compound 2 with MOMCI, DIPEA, and NaI in
CH2C12 was stirred at reﬂux overnight and subsequent chromatographic separation
provided us MOM-protected ketone precursor 41 in good yield. Having the compound
41 in hand, we investigated the dehydrogenation with freshly prepared IBX. Under the

triﬂuoroacetic acid (TFA) catalyzed conditions, 58 (A/B cis) ketone 41 in DMSO

43

(0.08M) was smoothly transformed at room temperature into dehydrogenated 4-en-3-one
compound 42 in 73-77% yield by the action of IBX.

24

 

MOMCI (6.1 equiv)
DIPEA (9.2 equiv)
Nal (10 mol%)
CHQCIQ, reflux
overnight, 76-83°/o

 

COQMG

IBX (2 equiv)
TFA (30 mol%)

 

DMSO (0.03M)
rt, 7 d 42 (73-77%)

 

Scheme 22. Dehydrogenation of compound 41 into enone 42 with IBX
Some key features of IBX chemistry are worth noting. IBX was synthesized from

oxidation of o-iodobenzoic acid by treatment with oxone, following the literature

method.50 IBX prepared by this method is reported to be non-explosive and nontoxic.

Although reaction times are long (1 week), the conditions are mild and not sensitive to
moisture, so the DMSO solvent does not have to be dry. Another feature is that the
formation of double bond is regioselective giving 4-en-3-one 42 as a major product. That
said, we did isolate minor amounts of by-products that included mixtures of 1,4-dien-3-
one 43 and 1-en-3-one 44 (~10%), and y,0—eliminated 4,6-dien-3-one 45 (<2%). This

regioselectivity may be derived from the enolization step of compound 41 with IBX. As

44

illustrated in Scheme 23, 58 (A/B cis) compound 41 has six major 1,3 diaxial interactions
around A/B ring junction, including interactions of 701-O<->401-H, 401-HH901-H, 901-
HH201-H, 901-HH701-O, lO8-MeH68-H, and 108—MeH88-H. Whereas enolization at
C4 (or unsaturation between C3 and C4) removes two 1,3-diaxial interactions relating
with 401-11, enolization at C2 (or unsaturation between C2 and C3) eliminates only one
interaction associated with 201-H. Also, 8-hydride elimination of C4-enolized
intermediate 46 creates more substituted double bond (42) than would be present in C2-
enolized intermediate 47, which generates the less substituted double bond in 44.
Among the isolated enone compounds, compounds 43 and 44 are recyclable with respect
to allomerization, but y,0-eliminated product 45 is a dead-end compound. When the
reaction is run at 0.08M concentration, we observe a precipitation of o-iodosobenzoic
acid (IBA), which is a by-product formed after oxidation with IBX when the reaction is

done. This makes for easy reaction monitoring. Thus an easy ﬁltration, followed by

chromatographic separation delivered 4-en-3-one compound 42 as a major product.

  

42 (73-77%)

 

 

 

 

 

Scheme 23. Regioselective enolization of 58 (A/B cis) 41 with IBX for enone formation

45

With this isolated pure 4-en-3-one compound 42 in hand, we set out to explore the

next Step, the stereoseletive reduction of 4-en-3—one to 501 (A/B trans) 3-keto product.

3.3. Stereoselective Reduction
3.3.1. Birch reduction
We commenced our stereoselective reduction studies with a Birch reduction of

our enones. as this should guarantee full stereoselection to the 501 (MB trans) compounds

. 27,29,34,”5
(see section 1.4). ' 3

Generally, Birch reductions are carried out on related enone substrates bearing a
carboxylic acid at C24. While carboxylic acids stay intact under Birch conditions, esters

tend to be reduced to aldehydes or alcohols by the action of the dissolving metal. Such a

. . . 51 . . . .
reaction 1S often referred to as Bouveault-Blanc type reductions. Utilizmg this fact, the

Zhou group carried out the Birch reduction on 4-en-3-one substrate 39 having an ester

functional group at C24 to afford allomerized 501 (MB trans) compound 40 that bears the

reduced aldehyde at C24 in high yield (Scheme 24).47

Li/NH3(/). -73 °c

    

then, quench with NH4CI

OMOM 73%

39

 

Scheme 24. Zhou’s stereoselective conjugate reduction with concomitant reduction of

ester to 501 (A/B trans) 3-keto aldehyde

Conjugate reduction of the enone with concomitant reduction of the ester is more
attractive than conjugate reduction alone, because the resulting product 501 (A/B trans) 3-
keto aldehyde is on the path to 3kPZS and its analogs. Prior to the last sulfation to
3kPZS, precursor 3kPZ has the hydroxyl functional group at C24. Thus, in order to
prepare 3kPZ, the carboxylic acid or aldehyde at C24 should be reduced to alcohol
functionality. While reduction of carboxylic acid requires ketone protection at C3,
aldehyde at C 24 can be reduced selectively over the ketone at C3. Additionally, substrate
similarity between 4-en-3-one 39 and 4-en-3-one 42 led us to explore the Birch reduction
of enone ester 42.

AS illustrated in Scheme 25, 4-en-3-one ester 42 was reduced under the dissolving
metal conditions. The Birch reduction delivered trace amounts of 3-keto ester 48, 29%
yield of the desired 3-keto aldehyde 49, and also small amount of a mixture of 49 and
overreduced 3-hydroxyl alcohol 50. As anticipated, the stereochemistry of the NB ring

junction of all products is 501 (A/B trans).

47

24
COgMe

 

Li/NH3(/). THF
-73 °C, 1.5 h

  
    

 

then, quench with NH4CI O H "’OMOM

50/49 (trace)

Scheme 25. Birch reduction of "’OMOM

4-en-3-one ester 42 Ft

Conjugate reduction along with Bouveault-Blanc type reduction gave us mixtures
of compounds bearing ketone/alcohol functionality at C3 and ester/aldehyde/alcohol
functionality at C24, as a single A/B trans isomer at C5. We then hypothesized that
treatment of the crude reaction with Jones’ reagent would convert the alcohol at C3 to the
ketone and the aldehyde/alcohol at C24 to the carboxlic acid, accompanied with
deprotection of the MOM groups under the strong acidic conditions. This would clean up
the aforementioned mixtures from the reduction step. Methylation of the resulting 3-keto
carboxylic acid would afford 501 (MB trans) 3-keto ester 1. With this hypothesis in

mind, we modiﬁed the Birch reduction sequence (Scheme 26). 1) After quenching the

Birch reduction of compound 42 with NH4C1, the crude reaction in CH2C12 was washed

with water and brine. 2) The concentrated material was dissolved in acetone and stirred

at room temperature for 30 minutes with Jones’ reagent, CrO3/HZSO4, after which the

48

reaction was quenched with excess isopropanol to generate turquoise colored chromium
precipitates. The precipitates were ﬁltered and the ﬁltrate was concentrated and
redissolved in MeOH. 3) After the TMSCI promoted methylation, ﬁnal work-up and
chromatographic separation provided us single compound of 501 (MB trans) 3-keto ester
1. Before the last methylation at C24, puriﬁcation was not necessary but the yield of l
varied from 18 to 65%.

MOMO

    

 

1) Li/NH3(I). THF, -73 °C, 1.5 h

  

2) Cr03/H2804, acetone, rt, 0.5 h :
OMOM 3) TMSCI (2.5 equiv) 0 H OH
42 MeOH, rt, overnight 1 08-65%)

 

Scheme 26. Modiﬁed sequence of Birch reduction to convert 42 to 501 (A/B trans) 1

During this sequence, we followed the reaction sequence step by step with lH-
NMR and made a few interesting observations. Under the strong acidic conditions of the
Jones’ oxidation, the MOM groups were still intact but methylation with TMSCI
deprotects two MOM groups. Moreover, it turns out that the yield of product 1 critically
depends on the quenching time of the Jones’ oxidation. After quenching the Jones’
oxidation with iSOpropanol, we saw formation of chromium precipitates, and these
precipitates got aggregated to make beads as time went on. Filtration of the precipitates
right after the quench requires additional washings with organic solvents and was slower
than ﬁltration of beads. However, the yield of product 1 diminished, as the quenching
time of the Jones’ oxidation got longer (Scheme 27). Perhaps that is because some of
product was trapped inside the beads of chromium. Finally, we established that the fast

quench of chromium reaction was the best conditions for the Birch modiﬁed sequence.

49

With this protocol, we obtained good yields over three steps without needing any

puriﬁcation of intermediates between steps.

 
  
 

1) Birch reduction

 

2) Jones' oxidation; then

 

 

 

O ”'OMOM quench with Isopropanol
42 3) methylation
2) quenching 1
time yield (%)
<5 min 60—65
3 h 49
Scheme 27. Yield of product 1 depending on 9 h 35
the quenching time of Jones' oxidation 18 h 18

 

Although the Birch reduction afforded full stereoselection to 501 (NE trans), the
practicality of these reductions is compromised by the need for cryogenic and
scrupulously dry conditions. Additionally, handling of liquid ammonia would be an issue

for large-scale synthesis. Thus, we gave our attention to other reduction methods.
3.3.2. SET Reduction with Smlz

The Birch reduction is a single-electron-transfer (SET) process. We observed
conjugate reduction along with over-reduction of 4-en-3-one ester 42 at C3 and C24.

Normally steroidal esters are known to be tolerant to SmIz reductions, which are also

. . 52 . . .
Single electron transfer reactions. Even though reduction With Smlz requrres

completely dry conditions, the reactions can be run at room temperature. Thus, we

applied reduction with Smlz to our 4-en-3-one ester 42, as depicted in Scheme 28. SmIz

was generated in-situ by addition of CH212 to samarium metal suspended in THF.53 The

50

deep blue color of CH212 solution changed into a deep violet upon the addition of
HMPA. Unfortunately, addition of substrate 42 immediately quenched the generated
Sm12 solution turning it into a yellow suspension. AS a result, the reaction with substrate

42 di (1 not take place and starting material was recovered quantitatively.

MOMQ "'3 24 MOMQ

         

Sm (2.7 equiv)
CH212 (2.4 EQUIV) X
HMPA (9.6 equiv) ;
42 Ta": H 43

 

Scheme 28. Conjugate reduction of 4-en-3-one ester 42 by in-situ generated Smlz

3-3.3. SET Reduction with sodium dithionite (NaZSZO4)

We turned our attention to other SET reductant, namely sodium dithionite
(N a28204). This reagent is nontoxic, inexpensive, and industrially attractive. Literature
examples showed that N32S204 is a very efﬁcient reagent for reducing steroidal 4-en-3-

One compounds to their corresponding 501 (A/B trans) stereoisomers (Scheme 29).54

. 54 .
Furthemore, Na2$204 tolerates ketones at C3 and sterordal esters. N32S204 IS an

inorganic reductant, and thus the reaction is typically run in a biphasic solution in the
presence of a phase transfer catalyst (PTC). Normal reaction conditions may need high
temperature but this is preferred over the cryogenic conditions at large scale. More

importantly, the reaction is not sensitive to moisture or air, so open-to-air conditions

Would be acceptable.

51

. NaQSQO4 (9 equiv)
” NaHCO3 (8 equiv)
o ’ PTC (9 equiv) o

toluene/H20 (1 /1 ) H
51 reflux, 2 h, 33% 52 (5a)

 

 

Scheme 29. Stereoselective conjugate reduction of 4-en-3-one 51 with Na28204

When the reaction was attempted on 4-en-3-one 42 (Scheme 30), the enone was

dissolved in toluene and mixed with a solution of sodium bicarbonate and N328204 in

water. PTC was added to the solution and the reaction mixture was allowed to reﬂux

prior to work-up. We tested two different PTCS, n-C15H31NMe3Br and Aliquat 336®.

The ﬁrst PTC in entry 1 provided us 17% recovery of starting material 42 and 71%
combined yield of inseparable mixtures of 41/48 (58/501) but selectivity was low
(58/501=1/1.5). The second PTC, Aliquat 336® (entry 2) gave interesting results. The
initial conjugate reduction products 41/48 (58/501) were formed in only 9% yield with
Similar selectivity (58/501=1/ 1.8) but we also isolated over-reduced products 53/54 in
84% yield. Indeed, both 53/54 mixtures contained four isomers. Hydroxyl groups of

both 53 and 54 isomers are epimeric at C3. Although there were possible complications
in determining ratios of 58/501, 1H-NMR spectrum Showed clear separation of two sets of
78-H and l28-H signals, revealing a selectivity of 1 to 5.5 favoring the 501 (A/B trans)
stereoisomer. Since we noticed that Jones’ oxidation could oxidize both epimers of the

C3 alcohols to a single ketone and without loss of the MOM groups, we reoxidized the

53/54 mixtures to ketones 41/48 under the Jones’ oxidation conditions. The overall yield

52

of the reoxidized 41/48 was still good at 81% and the 58/501 selectivity showed the same

as 1 to 5.5 ratios favoring the 501 (A/B trans) stereoisomer.

  
  
  
  

24
002MB 41 I48 (58/50)

 

 

 

o "’OMOM
N828204 (9 GQUIV) +
NaHCO;, (8 equiv) MOMO 24
PTC (9 equiv) E COzMe
toluene/H20 (1/1)
reflux
. 51/52 (SB/501)
Ho "OMOM
H
Yield
Entry PTC

41 I48 (513/561) 51/52 (513/501)

 

1 n-C15H31NMeaBr(0.5 h) 71%(1/1.5)a

9% (1/1.8) 84% (1/5.5)

2 Ali uat336® 2h
q ( ) 31% (1/5.5)b

 

a) 17% of starting material 42 was recovered.
b) reoxidized from 51/52 mixture by Jones [0]

Scheme 30. Stereoselective conjugate reduction of 4-en-3-one 42 with Na28204
This result was quite interesting. The selectivity of initially isolated 41/48
(58/501='1/1.8) mixtures was different from the selectivity of reoxidized 41/48
(58/501=1/5.5) mixtures. After the ﬁrst conjugate reduction of enone to ketone mixtures,
the second reduction may induce rate difference in conversion of 41/48 (58/501) mixtures
to alcohols, favoring 501 compound. Thus we asked if another way to separate 58 (A/B

cis) and 501 (MB trans) mixtures would be to use kinetic resolution by selective reduction

of the 5 8/501 3—keto mixtures with NaZSZO4.

53

Although the reductions with N328204 were promising, the reactions were not

without their Shortcomings. The reactions were not completely stereoselective for the
desired 501 (A/B trans) stereochemistry. Additionally, the 41/48 (58/501) mixtures after
conjugate reduction were not separable even with chromatographic separation.

Having explored single electron transfer processes for the stereoselective
reduction of enone compounds to 501 (MB trans) isomers, our attention next turned to
other reduction methods.

3.3.4. Directed hydrogenation with Crabtree’s catalyst
Selective hydrogenation could be achieved with metal hydride delivery directed

by metal complexation with pr0per functional groups on the substrate. Crabtree’s

catalyst has been utilized for selective hydrogenation directed by functional groups.55

Ketones, especially, are among the functional groups that can direct hydrogenation with

Crabtree’s catalyst.

002Me (Dr-'4

Crabtree cat. (5X6 mol%)
H2 bubbling

 

CHZCIZ, rt, 25 h

 

10% 41 (53)
73% 42

Scheme 31. Directed hydrogenation of 4-en-3-one 42 with Crabtree’s catalyst

Having a ketone functional group in enone 42, we looked to hydrogenate this

compound with Crabtree’s catalyst (Scheme 31). H2 gas was bubbled into a solution of

enone 42 in CH2C12 that was stirred at room temperature under the Crabtree catalyst

54

conditions. The hydrogenation was slow and the additional Crabtree’s catalyst needs to
be added portion-wise over the course of the reaction. Most of the starting material 42
was recovered (78%) and only 10% conversion to reduced ketone product 41 was
observed with complete stereoselectivity favoring 58 (A/B cis) isomer, and not the
desired 501 (A/B trans) isomer.
3.3.5. Stereoselective reduction with in-situ Cu-H

Several Cu mediated conjugate reductions with selective hydride delivery have

been reported. Recently, Buchwald and co-workers demonstrated a in-siru generated Cu-
. . . 56 . . .
H catalyst for stereoselective conjugate reductions. Followrng this literature report, we

carried out the conjugate reduction of enone 42 catalyzed by in-situ Cu-H as illustrated in
Scheme 32. A solution of enone 42 in toluene was added dropwise via cannula into the
in-situ generated Cu-H solution resulting from a mixture of carbene ligand and CuCl2 that
was treated with base and polymethylhydrosiloxane (PMHS) in toluene. The reaction
mixture was stirred at room temperature for 8 hours prior to work-up to deliver 3-keto
compound 41 in 16% yield and 65% yield of the over-reduced alcohol 53. However,

both products were determined to have exclusively the 58 (A/B cis) stereochemistry.

55

i-Pr i-Pr

0:; )0
COzMe

 

ligand/CuCl2 CH20 (1 mol%)

 

NaOt—Bu (6 mol%) MOMO
PMHS (3.0 equiv) 5
toluene, rt, 8 h

  

. 55% 53 (53)
"OMOM

Scheme 32. Stereoselective conjugate reduction of enone 42 with in-situ Cu-H
As metal-hydride reduction of enone substrate 42 with MOM protecting groups
only afforded the 58 (A/B cis) stereochemistry, we decided to focus on the free 701-
hydroxyl group as a directing group.
3.3.6. Directed hydrogenation with Wilkinson’s catalyst
As discussed in Chapter 1 (see section 1.4), the Mclean group previously carried

out reductions with Wilkinson’s catalyst to set up the 501 (A/B trans) stereochemistry of
compound 1 (Scheme 33).32 Here the selectivity might come from hydride delivery

directed by catalyst complexation with the free 701-hydroxyl group.

56

Ph3R, cPPh3
Rh

COQMG ' ,
Ph3P Cl
Wilkinson cat. (50 mol%)
H2 gas

V

bezene/ethanol (1/1)
rt, 25 h, 50%

   

 

H Petromyzonol PZ

Scheme 33. McLean’s stereoselective reduction of dienone 10 with Wilkinson’s catalyst

Since we prepared 1 to 1 mixtures of 1,4-dien-3-one 10 and 4-en-3-one 13 (see
section 3.2) and both components of the mixture contain a free 701-hydroxyl group,
selective hydrogenation with Wilkinson’s catalyst might be possible through hydroxyl
direction. A solution of enone mixtures 10 and 13 with Wilkinson’s catalyst in
benzene/ethanol was charged with H2 gas and allowed to stir at room temperature as
depicted in Scheme 34. Unfortunately in our hands, the reaction did not take place even
with three different batches of catalyst. This was not entirely surprising as the authors of
the original paper acknowledged that the reaction proved inconsistent and was catalyst-

batch dependent.

    

 

HO
5 0020/19
. Wilkinson's cat. (50 mol%)
H2 gas
0 "'OH benzene/H20 (1/1), rt

 

10/13 (NA/214:1 /1)

Scheme 34. Directed hydrogenation of enones 10/13 with Wilkinson’s catalyst

57

3.3.7. Selective reduction via internal hydride delivery
With unsuccessful results of hydride delivery via metal complexation with a

directing functional group, we turned our attention to the internal hydride delivery.

C-H activation

Internal H' delivery C-C coupling
’ /'_\ " ' F“) T
O [—1 , ('9 e 9
HO OH (02 equw) O CO‘BFa'Etgo O (O‘BFa'Etzo

BF3-Et20 (0.5 equiv)

H CH2012 L” 56 H 57
o’kPh 50°C, 24h, 7m oﬁph Q¢Ph

 

 

 

 

 

 

55 H2O _ ‘ " ® "‘
H20
BF3-Et20
0
“.Ph
Scheme 35. Sames' protocol of C-H activation 0
(or internal hydride delivery), followed by C-C coupling 58

The Sames group has focused on C-H activation or internal hydride delivery,

followed by C—C coupling as shown in Scheme 35.57 Benzyloxy enone 55 undergoes in—

situ acetal formation, and then it is activated by Lewis acid to become intermediate 56.
The lone pair electrons on oxygen serve to deliver a hydride to an activated enone acetal.
The resulting enol intermediate 57 undergoes C-C coupling with an aldehyde electrophile
to relieve the resultant oxonium species. Then, hydrolysis of the acetal selectively
affords product 58 in high yield. We have substrate similarity here. Our enone substrate

42 bears 701-hydroxyl group, which is two carbon units away from enone.

58

€3-56
l'l'l

W

O OBn

r—\
O H,3 O
0 "can U
Lewis Acid
59 60

Stereoselective Reduction
vla Internal H’ Delivery

 

 

 

J

 

 

9 E
COQMe l"A\ .
<1 OBn
O H ,O
Tun-"-7" ------- G) +H2O
,__, 61
HO OH Lewis Acid __ j

 

Scheme 36. Stereoselective reduction of enone 59 via internal hydride delivery

If the same chemistry could be applied to our substrate 59, with benzyl protection
at 701-hydroxyl group as shown in Scheme 36, acetal formation with activation by a
Lewis acid may lead to the similar complex intermediate 60. Then, the benzyl oxygen
may deliver the hydride to reduce the activated enone with stereoselectivity for the 501
(A/B trans) isomer to afford intermediate 61. Our hypothesis was that once the hydride
is delivered, intermediate 61 would have a rigid A/B trans fused ring and thus cannot
ﬂip. Consequently, instead of C-C coupling, in-situ generated water would hydrolyze
either the benzyl oxonium or the acetal to afford mono-deprotected 3-keto compound 62
with 501 (A/B trans) stereochemistry.

With this concept in mind, we prepared the substrate 59 (Scheme 37). Acid-
catalyzed benzyl protection was performed at the C7 and C12 hydroxyl groups.58

Dehydrogenation was carried out with IBX chemistry under the acid-catalyzed conditions

59

. 47 . . .
to afford corresponding precursor enone 59. Both sets of reaction conditions would

still need to be optimized for future applications.

HQ 24

 
 
 

CI3CC(NH)OBn (2.5 equiv)

 

 

TfOH (0.5 equiv))
O H '0“ CH2012/06H12 (1/2)
2 rt, 17 h, 13%

IBX (2.0 equiv)
TFA (30 mol%)
DMSO (0.11M)

1 rt, 7 d, 21%

I

 

Scheme 37. Preparation of precursor enone 59
with benzyl protection

 

Having this substrate enone 59 in hand, initial tests of the Sames’ protocol were
attempted (Scheme 38). A solution of benzyl protected enone 59, ethylene glycol, and
Lewis acid in CHzCl2 was allowed to stir at room temperature. The reaction was
monitored by TLC, but we did not see formation of any of the desired product 62 with the
501 (A/B trans) chemistry. Instead, we observed mono—deprotected compound 64 and

trace vii-eliminated 4,6-dien—3-one compound 65 by TLC. lntriguingly enough,
aldehyde formation was suggested by a leak at 0 = 10.01 ppm in the 1H-NMR spectrum

of the crude material. Presumably this is the result of reduction of ester at C24 or

hydrolysis of the oxonium intermediate. The possibility of internal hydride delivery in

60

this system should not be ruled out. Additional experimentations are required to

investigate this reaction further.

24
COgMG
/_.\
HO OH (0.2 equiv)
BF3'EI2O (0.5 equiv)
CH2012
rt

   

r—\
HO OH (0.2 equiv)
BF3'Et20 (0.5 equiv)

CH2012

  

0 "'0H
34

 

Scheme 38. Stereoselective reduction of enone 59 via internal hydride delivery

To sum up all the allomerization steps, we tried single step allomerization and
stepwise allomerizations. Up until now, the desired methyl 3-keto-allocholate 1 was
available from either single step allomerization with Raney Ni or Birch reduction
sequence of stepwise allomerization. Having crucial compound 1 in hand, we carried on

to the ﬁnal synthesis of male sea lamprey pheromones.

61

CHAPTER 4. SYNTHESIS OF MALE SEA LAMPREY PHEROMONES

AND FUTURE STUDIES

4.1. Synthesis of ACA

With the crucial compound 1 in hand, 3-keto allocholic acid (3kACA), one of the

male sea lamprey pheromones, could be easily prepared (Scheme 39), by saponiﬁcation
of the ester to carboxylic acid. A solution of compound 1 with K2CO3 in MeOH/HZO
was stirred at reflux for 2 days to afford a quantitative yield of 3kACA. The

spectroscopic data of synthetic 3kACA were matched with those of the natural product.

CO2M€

K2003 (5 equiv)

ll

 

MeOH/HZO (2/1)
reflux, 2 d
quant. yield

   

Scheme 39. Synthesis of 3kACA via saponiﬁcation of 501 (A/B trans) compound 1

4.2. Synthesis of 3kPZS

From the relatively straightforward transformation of compound 1, the synthesis
of 3-keto petromyzonol sulfate (3kPZS), which is the most potent component in male sea
lamprey pheromones, could be completed (Scheme 40). The key transformation of
compound 1 to 3kPZS would be reduction of ester to alcohol, followed by ﬁnal sulfation.
In order to achieve this sequence successfully, the ketone functionality of compound 1 at
C3 needed to be protected as an acetal, and deprotected after reduction of ester.

Although several acetal forming conditions were examined, Lewis acid catalyzed acetal

62

formation turned out to be the most practical method. Compound 1 with CuClz in a l to

1 mixture of ethylene glycol and dioxane was allowed to stir at reﬂux for 2 hours. This

. 59 . .
afforded clean acetal formation. Contrary to typical methods for acetal formation,

ethylene glycol and dioxane do not have to be dry and in-situ generated water did not
hamper acetal formation. Moreover, normal work-up and concentration provided
analytically pure acetal compound 31, which could be carried on to the next step without

any further puriﬁcation. Once the ketone at C3 was protected, the ester at C24 was

reduced with lithium aluminum hydride (LiA1H4).32 A solution of acetal protected ester

31 in THF was added dropwise to the suspension of LiAlH4 in THF. The reaction

mixture was stirred at reﬂux for 8 hours prior to work-up with Rochelle’s salt solution to
hydrolyze the aluminum salts. The resulting mixture was puriﬁed by column
chromatography to afford the acetal protected alcohol 66 in 81% yield. Acetal alcohol 66
was then deprotected with HCl aqueous solution in THF at room temperature to deliver

75% yield of 3-keto petromyzonol (3kPZ) after chromatographic separation. Lastly, the

primary alcohol at C24 of 3kPZ was sulfated following the literature method.60 3kPZ in

dry pyridine was treated with SO3'pyridine at room temperature. The reaction mixture

was quenched with MeOH and concentrated, followed by column chromatography to
provide us the main target of 3-keto petromyzonol sulfate (3kPZS) in about 12% yield.
The Spectroscopic data were identical to the natural material, but showed a minor amount
of the presumed disulfated product, which was also observed in the natural material by

the Li group (Michigan State University).

63

COzMe

  
  

  

CUCl2'2H2O (0.1 GCIUIV)

 

; O .
O H [OH HOCZH4OH/dioxane (1 /1 ) $0 H OH
1 ° ° 31
80 C, 3 h, 99 /o

   
    
 
 
 

LiAIH4 (4 equiv)
LiAIH4 (4 equiv) THF. reﬂux,
THF, reflux, 10 h 3 11.81%

; quenching w/ 5% H01 (aq.)
reflux, overnight. 57% ll

 

OH
5% H01 (aq.)
o S "'OH THF, rt, 12 h, 75%

 

SOg'py (1.2 equiv)
pyridine, rt, 1.5 d

 

Scheme 40. Synthesis of 3kPZS,
potent male sea lamprey pheromone

 

4.3. Synthesis of Larval Lamprey Pheromones, PZS and ACA
From our retrosynthetic viewpoint (see section 1.3), the 501 (A/B trans) compound

1 is the key intermediate for a plausible route to synthesize not only male sea lamprey
pheromones (3kPZS and 3kACA), but also larval lamprey pheromones (PZS and ACA).

Scheme 41 illustrates that the synthetic pathways to PZS and ACA from a common

intermediate. The compound 1 could be stereoselectively reduced at C3 with a bulky
hydride, KS-selectride to provide the 3a-hydroxyl as a single diastereomer.32 Hydrolysis
of the ester of compound 67 would lead to allocholic acid (ACA). On the other hand,
compound 67 could be transformed to the corresponding alcohol by LiAlH4 reduction.32

Then, selective sulfation of the resulting alcohol 68 would similarly afford petromyzonol

sulfate (PZS).60

002MB

KS-selectride

   

THF
LiAIH4 (4 equiv) : K2003
THF, reﬂux 3 MeOH/HZO
I’ ’ i

   

SOg'py (1.2 equiv)
pyridine, rt, 1.5 d

*--_..__----..-

Scheme 41. Synthesis of larval
sea lamprey pheromones, ACA and PZS

 

65

4.4. Conclusions and Future Studies
3-Keto petromyzonol sulfate, 3kPZS, is a potent component of the sex pheromone
cocktail emitted by male sea lamprey, petromyzon marinus. Such pheromones have been

successfully tested as population control agents against lamprey residing in the Great

Lakes.24 Owing to these results, a straightforward and practical synthetic route to 3kPZS

is needed. For the synthesis of 3kPZS, cholic acid was selected as the starting material,
because cholic acid has the carbon skeleton and functionality suitable for 3kPZS.
Allomerization to convert the stereochemistry from 5B to So was the crucial step in this
synthesis. Several allomerizations were conducted, including a single steps
allomerization with Raney Ni and a variety of stepwise allomerizations. Material derived
from allomerizations was used to establish a synthetic route to male sea lamprey
pheromones, 3kPZS and 3kACA. The search for a practical and scalable allomerization
of cholic acid and its derivatives continues. Even more, recently the Li group tested the

single component of synthesized 3kPZS in the ﬁeld: Synthetic 3kPZS induces upstream

movement of females and lures ~50% into traps.“ Due to this fascinating result, 3kPZS

should be continuously supplied via development of practical and environmentally
benign synthesis

Our synthesis of 3kPZS was successful, but more needs to be done in order to
make this a commercial process. As discussed in section 3.3.7, taking advantage of the

directionality of the 7a-hydroxyl groups would be promising way to induce
stereoselectivy at C5.57 Activated by Lewis acid, acetal formation promotes hydride

delivery from the benzyl protected 7a-hydroxyl group to establish the 5d

66

stereochemistry. However, the substrate preparations and reaction conditions are not yet

optimized.

24
COQMG

IBX (2 equiv)
TFA (30 mol%)

DMSO, rt, 48 h, 87%

   

CeCl37H20
NaBH4, MeOH,
0 °C, 1 h, 96%

 

24 24

002Me

NBSH, DEAD, PPh3

 

NMM, -30 to 0 °C

   

MCPBA, Ncho3
CH20I2, 0 °C, 6 h,
94%

24
COgMe

AcONa, AcOH,
45 °C, 48 h, 67%

   

Scheme 42. Oishi’s allomerization with Myers protocol

The Oishi group reported another allomerization directed by 3(3-hydroxyl group

instead of 7a-hydroxyl group (Scheme 42).62 Following Zhou’s IBX chemistry, they
Obtained the enone compound 70, which was allomerized using Myers protocol.63 A

ketone functional group was reduced by Luche conditions to 3(3-hydroxyl group.64 As a

67

key step, reductive 1,3-transposition of allylic alcohol was achieved with So (A/B trans)

stere ochemistry installation to afford olefin 72. The hydroxyl group was reinstalled
. . . 65 . . . 66
throu gh substrate-controlled stereoselective epoxrdation, followed by diaxral Opening

of the epoxide with acetate attack to obtain compound 74 as a single diastereomer.

    

MOMO 24
E COzMe
C9C|37H20
NaBH4
0 OMOM """"""" iii-90H

 

NMM,

 

OH

Fetizon's reagent

   

Scheme 43. Allomerization of enone 42 applying Oishi’s protocol

This sequence of allomerization could be applied to our system. As illustrated in

Scheme 43, an enone compound 42 may be reduced under the Luche conditions64 to

68

provide 3B-hydroxyl compound 75. Applying Myers protocol,63 5a (A/B trans)

stereochemistry could be installed via 1,3-transposition of allylic alcohol to afford oleﬁn

76. Then, the 3a-hydroxyl group would be reinstalled by stereoselective epoxidation,65
followed by diaxial attack66 of hydride alone with the reduction of the ester at C24 to
provide compound 78. According to the Tserng’s method,45 the 3a-hydroxyl group can

. . . . . 46
be selectively ox1dized W1th treatment of F etizon’s reagent.

The net function of the hydroxyl groups especially those bearing the or
stereochemistry in an allomerization might be tricky. If the hydroxyl group works as
directing functional group for the stereoselective reduction, it would install the Son (A/B
trans) stereochemistry. In other cases where the hydroxyl group does not serve as a
directing functionality, it may just serve as steric factor. As a result, reduction of enone
might give SB/Sa mixtures due to the steric interactions with the lOB-methyl group or
7oL-hydroxyl group. Therefore, if one of the competing groups, especially the 7(1-
hydroxyl group, loses directionality, the other completing group (lOﬁ-methyl group)
would govern the stereoselectivity of reduction to afford the 50 stereochemistry. With

this idea in mind, we propose another allomerization route (Scheme 44). Methyl cholate

12 could be converted to a diketo compound 80 via double oxidation with NBS67 and
. , 46 . 47 . . .

Fetizon s reagent, followed by MOM protection. Smooth dehydrogenation wrth IBX

could provide us mixtures of enones 81/82.47 Since the stereochemistry at C7 is lost, a

simple hydrogenation (H2 gas, Pd/C) could stereoselectively install the So (A/B trans)

69

stereochemistry due to the steric interaction between incoming hydrogen and lOB—methyl

group. OnceSa (A/ B trans) stereochemistry is set up, 3a and 70 hydroxyl groups can be

7
installed from reduction with KS-selectride.3" Lastly, 3a-hydroxyl group could be

. . . . _ , 46
selectively oxrdlzed wrth Fetizon s reagent.

24
COgMe

 
  
 
  
  

1) NBS
2) Fetizon's oxdiation

...................... .p

3) MOM protection

 

  
  

KS selectride
! THF

24
COgMe

Fetizon's oxidation

 

Scheme 44. Allomerization of enediketo compound 81/82

70

APPENDIX. EXPERIMENTAL DETAILS

General Materials and Methods

Tetrahydrofuran was freshly distilled from sodium/benzophenone under nitrogen.
Benzene, toluene, dichloromethane, triethylamine and chlorotrimethylsilane were freshly
distilled from calcium hydride under nitrogen. Benzene-d6, DMSO-d6, and chloroform-
d were purchased from the Cambridge Isotope Labs and used without further purification.
Deionized water was used unless otherwise noted.

All commercial reagents were used without purification unless otherwise noted.
Series of Raney Ni powders suspended in water were purchased from Aldrich.

Composition of no.2800 Raney Ni is Ni and Al, and size of the particle is 45-90

microns.68 Composition of no.4200 Raney Ni is Ni and AI, and size of the particle is 20-

50 microns.68 Flash chromatography was performed with silica gel 60 A (230—400

mesh) purchased from Silicycle. TLC was performed on aluminum backed TLC plates
by Silicycle. All other yields refer to chromatographically and spectroscopically pure

compounds. Melting points were determined on a Thomas-Hoover Apparatus,
. l 13
uncorrected. Infrared spectra were recorded on a Nicolet IR/42 spectrometer. H, C

NMR spectra were recorded on 300 and 500 MHz spectrometer with chemical shifts

reported relative to the residue peaks of solvent chloroform (6 7.24 for 1H and 6 77.0 for

l" . . . . . . .
JC). High-resolutlon mass spectra were acquired at the Michlgan State Unwersrty Mass

Spectrometry facility using a Waters QTOF Ultima mass spectrometer equipped with an

electrospray ionization (ESI) source by Luis Sanchez.

7l

Standard Reaction Method

All reactions were carried out in oven—dried glassware, with magnetic stirring, and
monitored by thin-layer chromatography with 0.25-mm precoated silica gel plates, unless
otherwise noted. Visualization of reaction progress was achieved by UV lamp,

phosphomolybdic acid stain or potassium permanganate stain.

Methyl cholate 12:

 

Into a 1 L round bottom ﬂask charged with
cholic acid (20.43 g, 50 mmol), which was

dissolved into MeOH (360 mL, 0.14M),

 

 

 

 

L TMSCI (12.8 mL, 100 mmol) was syringed in
and the solution open to air was stirred at room temperature overnight. Upon the full
conversion of starting material into product on TLC, reaction mixture was concentrated
with nitrogen gas blowing. During concentration, white solid was produced. The solid
was collected by suction ﬁltration and washed with deionized water (200 mLx3). The
ﬁltrate solution was evaporated to deliver the white precipitate, which was suspended in
deionized water (500 mL). Insoluble white precipitate was ﬁltered and the ﬁltered solid
was washed with deionized water (200 mLx3). The combined white solid was dried

overnight under high vacuum (80 °C) to provide desired product 12 (20.89 g, 49.5 mmol,
99% yield). Spectroscopic data matched literature reports.69

mp 154-155 °C (lit.7O mp 155-156 °C); 1H NMR (500 MHz, CDCI3) 6 (ppm) 3.96 (m, l
H), 3.84 (m, l H), 3.64 (s, 3 H), 3.43 (m, 1 H), 2.4-0.9 (m, 27 H), 0.96 (d, J = 5.9 Hz, 3
H), 0.87 (s, 3 H), 0.66 (s, 3 H); 13C NMR (125 MHz, CDCI3) 6 (ppm) 174.8, 73.0, 71.8,

72

68.3, 51.4, 50.2, 46.8, 46.3, 41.4, 39.3, 39.2, 35.2, 35.1, 34.7, 34.5, 31.0, 30.8, 30.1, 28.0,

27.4, 26.1, 23.1, 22.3, 17.1, 12.3.

Representative Single Step Allomerization with Raney Ni (Scheme 10 & 11)

To a pre—weighed two-neck round bottom ﬂask was added commercially available
Raney Ni in water suspension. The water was pipetted out, and washed with 2x25 mL
isopropanol and 2x25 mL p-cymene in the same manner. For about 250 wt% of Raney

Ni, methyl cholate 12 was added into the ﬂask, followed by p-cymene (0.19M). The

ﬂask was flushed with N2, and a mechanical stirrer was set up in the middle neck of the

ﬂask and the other neck was connected with an air condenser. Upon stirring, the ﬂask
was mechanically stirred at reﬂux for 10 hours. TLC (EtOAc) showed the starting
material was close to be consumed and a series of new spots was observed. The whole
mixture was cooled to room temperature and ﬁltered through celite. Filter cake was

washed with EtOAc till colorless and the cake was quenched with dilute HCl. The

solvent was concentrated with N2 blowing. The residue was then dissolved into

minimum amount of CH2C12 and puriﬁed by ﬂash column chromatography on

deactivated neutral alumina (CHzClz/EtOAc=1/3) to recover the starting material 12 (5-
10%), and isolate 513 (A/B cis) isomer 2 as white crystalline solid and SB/Sa mixtures
(~1/1 by NMR) with a trace amount of 4-en-3-one intermediate 13. After repeated
subjection of SB/Sa mixtures on the 3% deactivated neutral alumina, minor amount of 5a

(A/B trans) isomer 1 was isolated.

73

 

r ~ 518 isomer 2: mp 173-174 °c (lit.7] 170 °C); 'H

NMR (500 MHz, CDC13) 6 3.99 (m, 1 H), 3.89

(m, 1 H), 3.63 (s, 3 H), 3.67 (dd, J= 15.1, 13.7

 

 

 

Hz, 1 H), 2.44-2.08 (m, 7 H), 2.00-1.52 (m, 14 H),

 

1.41-1.27 (m, 4 H), 1.14-1.11 (m, 1 H), 0.96 (s, 3 H), 0.95 (d, J= 6.8 112,3 H), 0.69 (s, 3
H); 13C NMR (125 MHz, CDC13) 6 (ppm) 213.3, 174.8, 72.8, 68.3, 51.5, 47.2, 46.6,

45.5, 43.0, 41.8, 39.4, 36.7, 36.6, 35.2, 34.9, 33.8, 31.0, 30.8, 28.5, 27.4, 27.1, 23.1, 21.6,
17.3, 12.5.

50 isomer 1: mp 149-151 °c (lit.32 150—152 °C);

 

1H NMR (500 MHz, CDC13) 6 (ppm) 3.97 (m, 1

H), 3.85-3.84 (m, 1 H), 3.64 (s, 3 H), 2.38-2.02

 

 

 

(m, 8 H), 1.95-1.12 (m, 28 H), 0.97 (s, 3 H), 0.96

 

(d, J= 6.3 Hz, 3 H), 0.93-0.84 (m, l H), 0.69 (s, 3 H); 13C NMR (125 MHz, CDCl3) 6

(ppm) 211.7, 174.7, 72.6, 67.3, 51.5, 47.2, 46.5, 44.1, 41.9, 39.6, 39.1, 38.7, 38.0, 37.9,

36.5, 35.3, 35.1, 31.0, 30.8, 28.7, 27.3, 23.0, 17.3, 12.5, 10.3

a 4-en-3-one 13: mp 176-178 °C (lit.72 mp 178-179

°C); 1H NMR (500 MHz, CDCI3) 6 5.78 (s, 1 H),

3.98 (m, l H), 3.94 (m, l H), 3.63 (s, 3 H), 2.57-

 

 

 

‘3 0.99 (m, 23 H), 1.14 (s, 3 H), 0.95 (d, J = 6.1 Hz,

13
3 H), 0.71 (s, 3 H); C NMR (125 MHZ, CDC13) 6 (ppm) 198.9, 174.7, 167.7, 126.8,

74

72.3, 68.2, 51.5, 47.1, 46.3, 41.9, 40.8, 39.9, 38.8, 38.0, 35.2, 35.1, 33.8, 31.0, 30.8, 28.4,
27.3, 23.0, 17.3, 16.8, 12.5; HRMS (ESl+) (m/z) calcd for C25H39OS [M+H|+

419.2797, found 419.2799.

Separation of 58/50. mixtures

1 g of SB/Sa (1/ 1.1) mixtures was dissolved in acetone and EtOAc. 20 mL of
silica was added and the slurry was rotavapped dry. This powder was added to the top of
the column (d = 3.3 cm, 150 mL silica gel, hexane/acetone = 2:1) and dry. Eluent was
used to wash out and down the silica from the ﬂush and funnel. After 200 mL solvent, 8
mL fractions were collected. After 51 fractions, 408 mL of fraction was collected and
remaining was rinsed with acetone. An additional 175 mL solvent was collected. Second
column was performed with all fractions aﬁer 31 from the ﬁrst column. 10 mL of silica
gel was used for dryloading on column (d = 2.5 cm, 75 mL silica gel, hexane/acetone =
2:1). After 100 mL, 8 mL of fractions were collected by the total of 240 mL (30
fractions). 75 mL of acetone was added to top and another 20 fractions were collected.
Mixture fractions were collected and resubjected on the third column (d = 2.5 cm, 75 mL
silica gel, hexane/acetone = 2:1). The compound mixture was dissolved in eluent and
applied directly to the column. After 100 mL, 8 mL of fractions were collected. 0.472
mg of 5a (A/B trans) compound 1 was isolated with trace amount of hexane and some

impurity at 2.8 ppm but without 513(A/B cis) compound 2.

75

Preparation of compound 2 with Fetizon’s Reagent (Scheme 18)

Into a 1 L round bottom ﬂask charged with methyl cholate 12 (10.57 g, 25 mmol),
which was suspended into toluene (350 mL, 0.07M), AngO3 on celite (29.93 g from 1

mmol/0.5986 g batch, 50 mmol) was added. Onto the ﬂask were set up Dean-Stark trap
and reflux condenser with nitrogen balloon and the suspended mixture was reﬂuxed in
preheated oil bath at 135 °C for 8 hours. Upon full conversion into product on TLC,
reaction mixture was cool down to room temperature and precipitate was filtered on
celite. Filtered solid was washed with EtOAc (2x300 mL) and combined ﬁltrate solution
was concentrated under reduced pressure to provide crude material (10.26 g), which was

recrystalized with EtOAc to afford 8.94 g of product 12 in 85% yield.

 

Synthesis of Compound 41:
To an oven-dried 100 mL of round bottom ﬂask
was placed 4.206 g (10 mmol) of compound 2 and

150 mg (1 mmol) of Nal. The solid mixture was

 

 

 

suspended in 30 mL of CHzClz and then, 4.6 mL

(61 mmol) of MOMCl was added to the suspension. 16 mL (92 mmol) of
diisopropylethylamine was added slowly to the mixture under ice bath. The reaction

mixture was reﬂuxed for 8 hours. The reaction was quenched with 30 mL of sat.

NaHCO3 and transferred into separatory funnel. Organic layer was separated and
aqueous layer was extracted with 20 mL of CH2C12. Combined organic layer was dried

over NaZSO4 and concentrated under reduced pressure. The residue material was puriﬁed

76

by ﬂash chromatography on silica gel (Hexane/EtOAc = 3/ 1) to afford 4.230 g of white
solid in 83 % yield.

mp (softened at 63 °C) 70-71 °C; IR (NaCl) 2984 (s), 2951 (w), 1730 (s), 1708 (s) ch;

lH NMR (500 MHz, CDC13) 6 (ppm) 4.65 (d, J = 6.8 Hz, 2 H), 4.62 (dd, J = 95.7, 6.9

Hz, 2 H), 3.79 (m, 1 H), 3.65 (m, 1 H), 3.64 (s, 3 H), 3.37 (s, 3 H), 3.35 (s, 3 H), 3.34 (m,

1 H), 2.47-2.07 (m, 7 H), 1.99-1.23 (m, 15 H), 1.09-1.00 (m, 1 H), 0.98 (s, 3 H), 0.92 (d,

J = 6.4 Hz, 3 H), 0.69 (s, 3 H); l3C NMR (125 MHz, CDC13) 6 (ppm) 213.4, 174.7, 96.5,

96.0, 80.8, 74.8, 56.2, 56.0, 51.5, 46.3, 46.1, 45.1, 43.1, 41.9, 39.5, 36.7, 36.6, 35.5, 34.9,
31.1, 31.0, 30.6, 28.2, 27.7, 25.7, 23.4, 21.8, 17.6, 12.5; HRMS (ESI+) (m/z) calcd for

C29H4807Na [M+Na]+ 531.3298, found 531.3284.

Representative Dehydrogenation with Iodic Acid (Scheme 21):

1.759 g (10 mmol) of iodic acid was heated in 10 mL of DMSO at 80 °C for 1 hour with
light excluded from the reaction ﬂask. After cooling down to room temperature, 1 mL (1
mmol) of this readily prepared solution was added to a solution of 0.210 g (0.5 mmol) of
compound 2 and 0.13 mL (1.2 mmol) of cyclohexene in 0.5 mL of DMSO. The reaction
mixture was heated in the seal tube at 50 °C for 1.5 day, with light excluded from the

tube. The reaction mixture was diluted with 50 mL of ethyl acetate and washed with 20

mL of saturated NaHSO3 aqueous. solution and 20 mL of brine. The organic layer was

dried over NazSO4 and concentrated in vacuo to provide 0.50 g of crude material, which

77

was further puriﬁed by ﬂash chromatography on silica gel (CHgCIZ/EtOAFl/S) to

afford 91 mg (43%) of enone 10 and dienone 13 as a mixture (1/1 ratio by NMR).

Representative Dehydrogenation with IBX (Scheme 22):

To a 100 mL of 1 neck round bottom ﬂask was placed 1.017 g (2.0 mmol) of compound
41 and dissolved in 25 mL of DMSO. Into the solution was added 1.120 g (4.0 mmol) of
IBX and then, 52 mL (35%mol) of TFA was added slowly. The reaction mixture was
stirred at room temperature, monitored by TLC. Insoluble solid was formed in the course

of reaction. After 7 days, the reaction mixture was quenched with 28 mL of saturated

NaHCO; aqueous solution. To the suspension was added more 80 mL of H20 and

extracted with 4x30 mL of EtOAc. The combined organic layer was washed with 50 mL
of brine and dried over NaQSO4, followed by ﬁltration through a pad of celite. The

solvent was removed in vacuo to afford 1.09 g of crude material, which was further
puriﬁed by ﬂash chromatography on silica gel (Hexane/EtOAc = 3/2, v’/v) to provide 9
mg of impure starting material, 83 mg of impure 1-en-3-one, 15 mg of l-en-3-one/4-en-
3-one, 735 mg of pure desired 4-en-3-one 10 (73%), and 102 mg of 4-en-3-one/1,4-dien-
3-one (1/4 ratio) with accompanied by y,6-eliminated product, 4,6-dien-3-one 45.

mp 73-74 °C; IR (PTFE card) 2945 (s), 2821 (w),

 

1736 (s), 1671 (s), 1618 (w), cm"; 1H NMR (500

MHz, CDC13) 6 (ppm) 5.71 (s, 1 H), 4.63 (d, J:

 

 

 

7.1 Hz, 2 H), 4.62 (dd, J: 52.5, 6.9 Hz, 2 H), 3.75

 

(m, 1 H), 3.72 (m, 1 H), 3.62 (s, 3 H), 3.35 (s, 3 H), 3.31 (s, 3 H), 2.60 (dd, J= 15.1, 2.9

78

Hz, 1 H), 2.42-2.15 (m, 5 H), 2.04-1.21 (m, 14 H), 1.14 (s, 3 H), 1.13-1.06 (m, 1 H), 0.89
(d, J = 6.3 Hz, 3 H), 0.70 (s, 3 H); 13C NMR (125 MHz, CDC13) 6 (ppm) 198.8, 174.4,
168.6, 126.2, 96.6, 95.9, 80.4, 75.0, 56.0, 55.6, 51.3, 46.0, 46.0, 42.2, 39.9, 39.7, 38.4,
37.8, 35.3, 35.1, 33.8, 30.9, 30.8, 27.4, 25.7, 23.3, 17.4, 17.0, 12.3; HRMS (ESI+) (m/z)

calcd for C29H4607Na [M+Na]+ 329.3141, found 529.3146.

mp (softened at 60 °C) 67-68 °C; IR (NaCl) 3054

 

r 1
o

(s), 2984 (s), 2950 (w), 1733 (s), 1662 (s), 1614

(w), cm"; 1H NMR (500 MHz, CDCI3) 6 (ppm)

 

45 6.09 (m, 2 H), 5.64 (s, 1 H), 4.65 (m, 2 H), 3.79

 

 

(m, 1 H), 3.63 (s, 3 H), 3.33 (s, 3 H), 2.54-1.22 (m, 19 H), 1.07 (s, 3 H), 0.90 (d, J= 6.5
Hz, 3 H). 0.75 (s, 3 H); 13c: NMR (125 MHz, CDC13) 6 (ppm) 199.8, 174.6, 164.0,

141.4, 127.8, 123.5, 97.0, 96.8, 80.9, 56.2, 51.5, 47.2, 46.3, 45.9, 44.0, 37.7, 35.7, 35.4,
33.9, 33.6, 30.9, 27.5, 25.7, 23.2, 17.5, 16.2, 12.2; HRMS (ESI+) (m/z) calcd for

C27H4IOS [M+H]+ 445.2954, found 445.2959.

Representative Birch Reduction (Scheme 25):

A 100 mL of 3 neck round bottom ﬂask, which was equipped with dry condenser

and magnetic stirring bar, was charged with N2 gas and then flushed with NH3 gas. Dry
condenser was charged with dry ice and the reaction ﬂask was cool down to —78 °C to
start collecting about 15 mL of liquid ammonia. 56 mg of Li (8.1 mmol) was inserted

rapidly into this solution and stirred for 15 minutes until the color of the solution turned

into dark blue. A solution of 0.101 g of compound 42 (0.20 mmol) in 8 mL of dry THF,

79

was transferred to the ammonia via cannular over 5 minutes and washed/added (2x0.5

mL). The reaction mixture was stirred at the same temperature for 1.5 hour. The

reaction was quenched with 1.0 g of NH4C1. After the color of the solution turned back

1 to colorless, the Dewar bath was removed to evaporate ammonia gas overnight. Into the
suspension was added 20 mL of H20, and 1N HCl aqueous solution was added slowly to

pH 3. The solution was extracted with 3x30 mL of CHzClz and combined organic layer
was washed with 20 mL of brine and dried over Na2SO4. The solvent was removed in

vacuo to provide 0.12 g of crude mixture, which was further puriﬁed by ﬂash
chromatography on silica gel (25mmx130mm, hexane/EtOAc = 1/ 1, v’/v) to deliver trace
amount of desired 50. (A/B trans) product 48, 29% of aldehyde 49, and mixtures of 49

and 50 (trace).

mp 68-70 °C; IR (KBr) 2985 (s), 2952 (w), 1729

 

CH0 (s), 1707 (s) cm"; 'H NMR (500 MHz, CDC13) 6

  

(ppm) 9.75 (t, J = 1.8 Hz, 3 H), 4.65 (d, J = 9.5

 

é ”OMOM
49 Hz, 2 H), 4.62 (dd, J = 59.5, 7.0 Hz, 2 H), 3.74

 

 

 

(m, 1 H), 3.59 (m, 1 H), 3.38 (s, 3 H), 3.32 (s, 3 H), 2.37-0.86 (m, 24 H), 0.98 (s, 3 H),
0.91 (d, J = 6.6 Hz, 3 H), 0.69 (s, 3 H); 13C NMR (125 MHz, CDC13) 6 (ppm) 211.7,

203.0, 96.6, 96.2, 80.7, 74.6, 56.0, 55.6, 46.3, 46.3, 44.2, 42.3, 40.9, 39.8, 39.6, 38.1,
38.0, 35.4, 35.2, 33.9, 32.7, 27.9, 27.7, 26.1, 23.3, 17.7, 12.5, 10.5; HRMS (ESI+) (m/z)

calcd for C28H50NO6 [M+NH4]+ 496.3638, found 496.3651.

80

Modified Sequence of Birch Reduction (Scheme 26 & 27):

The exactly same Birch reduction step of enone 42 was carried out. After acidic work-up
and concentration, the crude material was checked by IH-NMR, which indicated that two
MOM protecting groups were intact and methyl ester at C24 position was reduced
completely incorporating generation of trace amount of aldehyde. The crude was

suspended in acetone (3 mL, 0.05M) and the solution was cool down to 0 oC, followed by

the addition of Jones’ reagent (0.5 mL, 1.33 mmol from 2.67M aqueous solution of

CrO3/H2804) to provide red solution. After 30 minutes at room temperature, the
solution was quenched with isopropanol (3 mL) at 0 °C to produce turquoise precipitate,
which was ﬁltered out right away through celite. The ﬁlter cake was washed with
acetone (20 mLx3) and the ﬁltrate solution was concentrated under reduced pressure to
deliver crude material (53 mg), which has MOM protecting groups attached. The crude
was dissolved in MeOH (3 mL, 0.05M), followed by the addition of TMSCI (0.1 mL,

0.78 mmol). The mixture was allowed to stir at room temperature overnight. Most of

methanol was evaporated and water (15 mL) and saturated NaHCO3 aqueous solution (15
mL) were added, which then mixture was extracted with CH2C12 (25 mLx3). The

combined organic layer was dried over Na2SO4 and concentrated under reduced pressure

to give yellow crude, which indicated no presence of MOM protection with trace amount
of aldehyde. The crude was further puriﬁed by ﬂash chromatography on silica gel

(100mmx15mm, CHzClz/EtOAc = 1/3) to provide up to 65% yield of desired 5a (A/B

trans) product 1.

81

Representative Conjugate Reduction with Na28204 (Scheme 30)
To a 50 mL of 1 neck round bottom ﬂask was prepared the solution of 0.101 g (1.20

mmol) of NaHCO3 and 0.546 g (1.35 mmol) of Aliquat® 336 in 6 mL of H20. Into the

solution was added the solution of 0.076 g (0.15 mmol) of compound 42 in 6 mL of

toluene. To the solution mixture was added 0.235 g (1.35 mmol) of Na28204 and

reﬂuxed for 2 hours. The reaction mixture was cooled down to room temperature and 20

mL of H20 was added. The organic layer was separated and the aqueous layer was

extracted with 3x30 mL of EtOAc. The combined organic layer was dried over NaZSO4.

The solvent was removed in vacuo to afford 0.081 g of crude material, which was further
puriﬁed by ﬂash chromatography on silica gel (Hexane/EtOAc = 2/1, v’/v) to provide 7
mg of reduced products 41/48 (ratio of SB/Sa = 1/1.8, 9 %), and 65 mg of overreduced
alcohol mixtures of 53/54 (SB/5a = 1/5.5, 84%). The overreduced mixtures were
dissolved in 2 mL of acetone, followed by addition of Jones’ reagents (1 mL, 2.67
mmol) until the solution was turned into red at 0 °C. The excess of Jones’ reagents was
quenched with isopropanol at 0 °C and the solution was ﬁltered through celite. The
ﬁltrate was concentrated under the reduced pressure to give 66 mg of crude mixture,
which was further puriﬁed by ﬂash chromatography on silica gel (Hexane/EtOAc = 2/1,

v’/v) to obtain 61 mg of oxidized product 41/48 (ratio of 5(3/50t = 1/5.5, 81%).

82

Synthesis of Compound 63:

 

Into a 1 neck of round bottom ﬂask (50 mL) was

placed compound 2 (0.2103 g, 0.50 mmol),

 

which was dissolved in cyclohexane/CH2C12

 

 

 

(2/1, 14.5 mL). Following the addition of benzyl trichloroacetimidate (230 mL, 1.24

mmol), mixture was cool down to 0 °C, at which a 0.5M solution of

triﬂuoromethanesulfonic acid in cyclohexane/CH2C12 (2/ 1) (0.5 mL, 0.25 mmol) was

added dropwise into the mixture. The resulting mixture was stirred at room temperature

overnight. During the course of reaction, the color of the solution was getting brown.

After 17 hours, the mixture was diluted with CH2C12 (10 mL) and then, quenched with
H20 (10 mL). All the mixture was transferred into separatory funnel and washed with
saturated NaHCO3 aqueous solution (20 mL). Layers were separated and the aqueous
layer was extracted with CH2C12 (10 mL). The combined yellow organic layer was

washed with brine (30 mL) and dried over Na2SO4 (3.05 g) and concentrated to deliver

red brown crude, which was further puriﬁed by ﬂash chromatography on silica gel
(100mmx24mm, EtOAc/hexane = 1/6 9 EtOAc/hexane = 1/1) to provide the desired

product 63 in 13% yield.

IH NMR (500 MHz, CDC13) 6 (ppm) 7.33-7.19 (m, 10H), 4.49 (dd, J= 35.5, 12.2 Hz, 2
H), 4.42 (dd, J = 168.7, 11.5 Hz, 2 H), 3.72 (m, 1H), 3.64 (s, 3 H), 3.51 (m, 1 H), 2.24-

1.04 (m, 24 H), 0.98 (s, 3H), 0.92 (d, J = 6.3 Hz, 3 H), 0.73 (s, 3 H); 13C NMR (125

83

MHZ, CDC13) 6 (ppm) 213.1, 174.8, 139.7, 138.8, 128.3, 127.4, 127.3, 127.1, 126.7,

80.8, 75.6, 70.7, 70.0, 51.4, 46.5, 46.3, 44.6, 43.5, 42.3, 39.9, 36.7, 36.7, 35.2, 34.9, 31.1,

31.0, 28.5, 27.5, 23.4, 23.4, 21.8, 17.6, 12.5.

Synthesis of Compound 59:

 

A 20 mL of vial was charged with starting
material 63 (0.0378 g, 0.063 mmol), which was

dissolved in DMSO (0.57 mL, 0.11M). Into the

 

 

 

 

solution was added IBX (0.0353 g, 0.126
mmol) and then, TFA (1.4 mL, 0.019 mmol) was added. The reaction mixture was

stirred at room temperature for 7 days to start forming insoluble solid and then, the

reaction mixture was quenched with 2 mL of saturated NaHCO3 aqueous solution. H20

(20 mL) and CH2C12 (20 mL) were added into the mixture and then whole mixture was

transferred to separatory funnel. The funnel was shaken to extract organic material to

bottom layer and settled down. Layer was separated and aqueous layer was extracted
with another fresh CHzClz (20 mL). The combined organic layer was washed with brine
(30 mL), dried over NaZSO4 (2.17 g) and concentrated under reduced pressure to deliver

crude material (0.0398 g), which was further purified by ﬂash chromatography on silica
gel (l90mmx24mm, EtOAc/hexane = 1/2) to provide the desired enone compound 59 in

21% yield.

84

1H NMR (500 MHz, CDC13) 6 (ppm) 7.32-7.21 (m, 10H), 4.46 (dd, J: 104.5, 12.0 Hz, 2
H), 4.44 (dd, J = 79.8, 12.0 Hz, 2 H), 3.69 (m, 1H), 3.63 (s, 3 H), 3.58 (m, 1 H), 2.63-
0.95 (m, 21 H), 1.15 (s, 3H), 0.88 (d, J = 6.3 Hz, 3 H), 0.72 (s, 3 H); 13C NMR (125
MHz, CDC13) 6 (ppm) 198.9, 174.7, 168.7, 139.5, 138.9, 128.2, 128.2, 127.3, 127.3,

127.1, 127.1, 126.3, 80.3, 75.1, 70.4, 70.1, 51.4, 46.3, 46.2, 42.3, 40.5, 39.9, 37.8, 36.6,

35.2, 35.1, 33.8, 31.0, 30.9, 29.7, 27.4, 23.3, 23.3, 17.5, 172,125.

Synthesis of Compound 31:

 

002MB To a solution of 0.10 g (0.238 mmol) of

 
 

compound 1 in 7.2 mL of ethylene

 

 

o _
{,0 H OH glycol/dioxane (1/ 1) was added 4.1 mg (0.024

 

mmol) of cupric chloride. The reaction mixture

was placed into the preheated oil bath at 80 °C and heated for 3 hours. The mixture was

poured into the 30 mL of H20 and extracted with 3x20 mL of diethyl ether. The extract
was dried over NaZSO4 and concentrated to provide 0.11 g of white solid in 99% yield.
mp 155-156 °C; IR (NaCl) 3430 (s, br), 2986 (s), 1729 (s) cm]; 1H NMR (500 MHz,

CDC13) 6 (ppm) 3.93 (m, 1 H), 3.90 (s, 4H), 3.80 (m, 1 H), 3.64 (s, 3 H), 2.38-2.32 (m, 1
H), 2.24-2.18 (m, 1 H), 1.95-1.07 (m, 28 H), 0.95 (d, J = 6.4 Hz, 3 H), 0.87-0.82 (m, 2
H), 0.78 (s, 3 H), 0.67 (s, 3 H); 13C NMR (125 MHz, CDCl3) 6 (ppm) 174.7, 109.1, 72.8,

67.7, 64.2, 64.1, 51.5, 47.2, 46.5, 42.2, 39.7, 39.2, 37.5, 36.2, 36.2, 35.6, 35.2, 35.1, 31.2,

85

31.0, 30.9, 28.7, 27.3, 23.0, 17.3, 12.6, 10.3; HRMS (ESI+) (m/z) calcd for C27H4SO6

[M+H]+ 465.3216, found 465.3215.

 

r ., ) Synthesis of Compound 66:

OH To oven dried 50 mL of 1 neck round bottomed

 
 

ﬂask was suspended 28 mg (0.72 mmol) LiAlH4

in 4.8 mL of THF. The separately prepared

 

 

o _
«,0 H mm

solution of 85 mg (0.18 mmol) of compound 31 in 4.8 mL of THF was added dropwise to

 

the suspension over 5 minutes. All the reaction mixture was set into the preheated oil bath
to 70 °C and reﬂuxed for 8 hours. Once the mixture was cooled down to room
temperature, 1 mL of Rochellie’s salt solution was added slowly and the mixture was
reheated to 70 °C to hydrolyze lithium salts for additional 12 hours. After cool down to

room temperature, the mixture was transferred to the separatory funnel and washed with

10 mL of H20 and 10 mL of brine. The organic layer was dried over NaZSO4 and

concentrated to afford 90 mg of mixture, which was further puriﬁed by ﬂash

chromatography on silica gel (EtoAc) to provide 65 mg of white solid in 81 % yield.
mp 194-196 °C; IR (NaCl) 3428 (s, br), 2986 (s) cm"; IH NMR (500 MHz, CDC13) 6

(ppm) 3.95 (m, 1 H), 3.90 (s, 4H), 3.80 (m, 1 H), 3.59 (td, J = 6.5, 2.0 Hz, 2 H), 1.95-1.80

(m, 3 H), 1.74—1.38 (m, 22 H), 1.36-1.22 (m, 4 H), 1.15-1.06 (m, 2H), 0.97 (d, J = 6.6 Hz,
3 H), 0.78 (s, 3 H), 0.67 (s, 3 H); 13C NMR (125 MHz, CDCI3) 6 (ppm) 109.2, 72.8,

67.7, 64.1, 64.1, 63.4, 47.3, 46.4, 42.1, 39.7, 39.0, 37.5, 36.2, 36.1, 35.5, 35.4, 35.2, 31.8,

86

31.1, 29.4, 28.5, 27.5, 23.1, 17.7, 12.6, 10.2; HRMS (ESI+) (m/z) calcd for C26H4SOS

lM+Hl+ 437.3267, found 437.3269.

Preparation of 3kPZ:

 

a) To 10 mL of 1 neck round-bottomed ﬂask was
placed 38 mg (0.087 mmol) of compound 66 and

dissolved in THF. Then, 0.3 mL of 5% HCl (aq.)

 

 

 

was added and the reaction mixture was stirred at

room temperature for 12 hours. Solvent was removed under reduced pressure and crude
mixture was ﬁltered through silica gel eluenting with CHgClz/EtOH (7/1). Filtrate was

evaporated to afford 35 mg of white solid, which then was puriﬁed by ﬂash
chromatography on silica gel with EtOAc to provide 25 mg of white solid in 75 % yield.

b) A 50 mL of 1-neck round bottom ﬂask was charged with LiAlH4 (0.066 g, 1.74
mmol), which was suspended into THF (7.7 mL) and was cool down to 0 °C. Into the
suspension, a solution of compound 31 (0.202 g, 0.435 mmol) in THF (5 mL) was added
dropwise via cannular over 5 minutes and the ﬂask was washed/added with THF (2x05
mL). The resulting suspension was reﬂuxed for 10 hours. Upon the complete
consumption of starting material on TLC, the mixture was cool down to room
temperature and quenched dropwise with 5% HCl aqueous solution (15 mL). The
mixture was reheated at 80 °C overnight to hydrolyze lithium salts and cooled down to
room temperature. The whole mixture was transferred to separatory funnel to let layers
separated and aqueous layer was extracted with EtOAc (50 mL). Combined organic layer

was washed with deionized water (50 mL) and brine (50 mL), and then dried over

87

NaZSO4 (5.2 g) and concentrated under reduced pressure to deliver white solid, which

then was puriﬁed by ﬂash chromatography on silica gel with EtOAc to provide 98 mg of

white solid in 57 % yield.

mp 172-173 °C; 1R (NaCl) 3427 (s, br), 2986 (s), 1707 (s) cm"; 1H NMR (500 MHz,

CDCI3) 6 (ppm) 3.99 (m, 1 H), 3.86-3.84 (m, 1 H), 3.60 (td, J = 6.6, 2.0 Hz, 2 H), 2.35-
1.82 (m, 8 H), 1.74-1.08 (m, 19 H), 1.36-1.22 (m, 4 H), 1.15-1.06 (m, 2H), 0.98 (d, J =
6.6 Hz, 3 H), 0.98 (s, 3 H), 0.71 (s, 3 H); 13C NMR (125 MHz, CDC13) 6 (ppm) 211.9,

72.8, 67.3, 63.4, 47.4, 46.4, 44.1, 41.9, 39.6, 39.2, 38.7, 38.0, 38.0, 36.5, 35.4, 35.3, 31.9,
29.4, 28.6, 27.5, 23. 1, 17.7, 12.6, 10.3; HRMS (ESI+) (m/z) calcd for C24H4lO4

|M+H|+ 393.3005, found 393.3001.

 

1 Synthesis of 3kACA:
To a 10 mL of l neck round-bottomed ﬂask were

added 0.100 g (0.238 mmol) of compound 1 and

 

 

 

0.164 g (1.20 mmol) of KZCO3. The mixture was

 

dissolved in 3 mL of HZO/MeOH (1/2) and reﬂuxed overnight. After cooling down to
room temperature, 2 mL of 1N HCl aqueous solution was added slowly. The solution
was transferred to separatory funnel and 2x20 mL of CH2C12 was extracted. The organic
layer was washed with brine (30 mL) and dried over NaZSO4 (3.5 g). The solvent was
evaporated under the reduced pressure to provide impure 96 mg of white solid in 99%

yield.

88

mp 189-191 °C; IR (NaCl) 3427 (s, br), 2984 (s), 1707 (s), 1609 (s) cm"; 1H NMR (500

MHz, DMSO-d6) 6 (ppm) 11.94 (s br, 1H), 3.77 (m, l H), 3.60 (m, l H), 2.42-2.07 (m, 5
H), 1.98—1.53 (m, 11H), 1.51-1.11 (m, 8 H), 0.92 (s, 3H), 0.91 (d, J = 6.4 Hz, 3 H), 0.61
(s, 3 H); 13C NMR (125 MHz, DMSO-d6) 6 (ppm) 210.8, 175.0, 70.9, 65.5, 46.1, 45.8,

44.0, 41.4, 39.5, 38.9, 38.2, 37.9, 37.8, 36.9, 35.0, 35.0, 30.8, 30.8, 28.9, 27.2, 22.8, 16.9,
12.3, 10.0; HRMS (ESI+) (m/z) calcd for C24H4lO6 [M+H3O]+ 425.2903, found

425.2906.

 

f ., Synthesis of 3kPZS:
To a ﬂame-dried vial was added 7 mg (0.016

mmol) of compound 3kPZ and dissolved in l

 

O H ’OH mL of pyridine, dried with KOH. Then, 5.1 mg

 

 

 

(0.032 mmol) of SO3-pyridine was added and

the mixture was stirred under N2 gas atmosphere at room temperature for 8.5 hours. The

reaction was quenched with 1 mL of MeOH and stirred for 15 minutes at room
temperature. The mixture was concentrated and puriﬁed through pipette column with
CHzClz/MeOH/acetic acid (100/10/ 1) to afford about 12% yield of 3kPZS. The fraction
which has low Rf value was gathered and checked by NMR and HPLC, comparing with

natural 3kPZS and 3kPZS synthesized by BridgeOrganics.
1R (NaCl) 3433 (3, br), 2944 (s), 2251 (s), 2125 (s), 1662 (s) cm'l; HRMS (ESI+) (m/z)

calcd for C26H47N207S [M+ACN+NH4]+ 531.3104, found 531.3116.

89

 

Table 1. Crystal data and structure reﬁnement for m1112404

 

Identiﬁcation code
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group

Unit cell dimensions

Volume

Z

Density (calculated)

Absorption coefﬁcient

90

m1112404

C32 H42 NO8
568.67

173(2) K
0.71073 A
Monoclinic
P2(1)

a = 7.3966(15) A
b = 12.178(2) A
c = 17.057(3) A
alpha = 90 deg.
beta = 101.18(3) deg.

gamma = 90 deg.
3

1507.3(5) A

2

1.253 Mg/m3

0.089 mm'1

n
o
= C
l
n..-

 

(Table 1. continued)
F(000) 610
Crystal size 0.4 x 0.2 x 0.2 mm

Theta range for data collection 2.07 to 28.16 deg.

Index ranges -9<=h<=9, -16<=k<=16, -22<=l<=22
Reﬂections collected / unique 18038 / 7076 [R(int) = 0.0296]
Completeness to theta = 28. 16 98.0%

Reﬁnement method F ull-matrix least-squares on F 2
Data / restraints / parameters 7076/ 1 / 370

Goodness-of-ﬁt on F2 0.773

Final R indices [I>23igma(I)] R1 = 0.0399, wR2 = 0.1044

R indices (all data) R1 = 0.0623, wR2 = 0.1183
Absolute structure parameter -0.4(8)

Largest diff. peak and hole 0.229 and -0.199 e.A-3

91

Table 2. Atomic coordinates ( x 104), equivalent isotropic

displacement parameters (A2 x 103), and occupancies for m1112404

 

 

x y z U(eq) Occ.
0(1) 6692(2) 6320(2) 4275(1) 58(1)
C(2) 5466(3) 6824(2) 4506(1) 41(1)
C(3) 3546(3) 6371(2) 4441(1) 38(1)
C(4) 3044(2) 6331(2) 5280(1) 28(1)
C(5) 3192(2) 7470(2) 5697(1) 27(1)
C(6) 5191(3) 7882(2) 5747(1) 36(1)
C(7) 5794(3) 7918(2) 4929(1) 44(1)
C(8) 1848(3) 8325(2) 5232(1) 35(1)
C(9) 1 158(2) 5793(2) 5246(1) 30(1)
C(10) 729(2) 5646(2) 6077(1) 27(1)
C(11) 927(2) 6724(2) 6551(1) 25(1)
C(12) 2808(2) 7292(2) 6560(1) 26(1)
C(13) 2973(3) 8358(2) 7061(1) 33(1)
C(14) 2599(2) 8200(2) 7913(1) 31(1)
0(15) 4077(2) 7534(1) 8345(1) 38(1)
C(16) 697(2) 7664(2) 7887(1) 28(1)

92

C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
0(27)
C(28)
0(29)
0(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)

C(38)

(Table 2. continued)

648(2)
-1128(3)
425(3)
266(3)
-841(3)
-331(3)
1021(3)

-591(3)

-1 153(3)

-2981(3)

-3044(2)

4794(4)

4271(2)
2085(2)
1485(3)
424(2)
3050(3)
4892(3)
6295(3)
5808(3)
3989(3)

2614(3)

6573(2)
6009(2)
6324(2)

7228(2)

8474(2)

8035(2)
8987(2)

7378(2)
8052(2)
8608(2)
9519(2)

10087(3)

7414(1)
7549(1)
8421(1)

8694(1)

7503(1)

9288(1)
9520(1)

10036(1)

10708(1)

10467(1)

10896(1)

10749(2)

8272(2) 9986(1)

4853(1)
3912(2)
3654(1)
3200(2)
3507(2)
2801(2)
1801(2)
1478(2)

2176(2)

93

6500(1)
6770(1)
6709(1)
7162(1)
7231(1)
7575(1)
7864(1)
7808(1)

7447(1)

27(1)
34(1)
37(1)
31(1)
34(1)
35(1)
47(1)
48(1)
51(1)
42(1)
64(1)
89(1)
56(1)
30(1)
28(1)
38(1)
29(1)
34(1)
37(1)
36(1)
40(1)

34(1)

(Table 2. continued)
C(39) 7290(3) 1045(2) 8241(1) 44(1) 1
O(40) 8850(2) 1200(1) 8123(1) 51(1) 1

C(41) 6876(3) 298(2) 8653(1) 73(1) 1

 

U(eq) is deﬁned as one third of the trace of the orthogonalized Uij tensor.

Table 3. Bond lengths [A] and angles [deg] for mll 12404

 

O(1)-C(2) 1.223(3)
C(2)-C(7) 1.51 1(3)
C(2)-C(3) 1.508(3)
C(3)-C(4) 1.547(3)
C(4)-C(9) 1.532(3)
C(4)-C(5) 1.553(3)
C(5)-C(8) 1.548(3)
C(5)-C(6) 1.548(2)
C(5)-C(12) 1.568(2)
C(6)-C(7) 1.547(3)
C(9)-C(10) 1.522(3)
C(10)-0(30) 1.477(2)
C(10)-C(11) 1.533(3)

94

(Table 3. continued)

C(1 1)-C(17)
C(1 1)-C(12)
C(12)-C(13)
C(13)-C(14)
C(14)-C(15)
C(14)-C(16)
C(16)-C(21)
C(16)-C(17)
C(16)-C(20)
C(17)-C(18)
C(18)-C(19)
C(19)-C(20)
C(20)-C(22)
C(22)-C(23)
C(22)-C(24)
C(24)-C(25)
C(25)-C(26)
C(26)-C(29)
C(26)-0(27)
0(27)-C(28)
0(30)-C(31)

C(31)-C(32)

95

1.537(2)
1.552(2)
1.546(3)
1.543(3)
1.444(2)
1.544(3)
1.551(3)
1.551(3)
1.564(3)
1.539(3)
1.551(3)
1.564(3)
1.538(3)
1.532(3)
1.548(3)
1.532(3)
1.496(3)
1.203(3)
1.335(3)
1.446(3)
1.342(2)

1.215(2)

(Table 3. continued)
C(31)-C(33)
C(33)-C(34)
C(33)-C(38)
C(34)-C(35)
C(35)-C(36)
C(36)-C(37)
C(36)-C(39)
C(37)-C(38)
C(39)-0(41)
C(39)-C(40)
O(l)-C(2)-C(7)
O(1)-C(2)-C(3)

C(7)-C(2)-C(3)
C(2)-C(3)-C(4)
C(9)-C(4)-C(3)
C(9)-C(4)-C(5)
C(3)-C(4)-C(5)
C(8)-C(5)-C(4)
C(8)-C(5)-C(6)
C(4)-C(S)-C(6)
C(8)-C(5)-C(12)

C(4)-C(5)-C(12)

96

1.497(3)
1.396(3)
1.398(3)
1.387(3)
1.388(3)
1.387(3)
1.479(3)
1.376(3)
1.223(3)
1.224(2)
122.4(2)
122.7(2)
114.81(18)
109.59(16)
111.05(15)
112.47(15)
112.77(15)
112.64(15)
108.78(15)
107.29(15)
111.00(15)

107.30(14)

(Table 3. continued)

C(6)-C(5)-C(12)
C(7)-C(6)-C(5)
C(2)-C(7)-C(6)
C(10)-C(9)-C(4)
O(30)-C(10)-C(9)
O(30)-C(10)-C(1 1)
C(9)-C(10)-C(1 1)
C(10)-C(11)-C(17)
C(10)-C(1l)-C(12)
C(1 7)-C(1 1)-C(12)
C(13)-C(12)-C(11)
C(13)-C(12)-C(5)
C(1 l)-C(12)-C(5)
C(14)-C(13)-C(12)
O(15)-C(14)-C(13)
O(15)-C(14)-C(16)
C(13)-C(14)-C(16)
C(14)-C(16)-C(21)
C(14)-C(16)-C(l7)
C(21)-C(16)-C(17)
C(14)-C(16)-C(20)

C(21)-C(16)-C(20)

97

109.74(14)
113.49(16)
110.99(17)
111.62(15)
106.66(14)
108.45(13)
112.01(15)
112.69(14)
112.39(14)
109.27(14)
110.76(14)
113.19(14)
112.16(14)
113.99(15)
107.14(15)
111.85(15)
110.75(15)
109.43(16)
107.87(14)
112.57(15)
117.30(15)

109.20(14)

 

(Table 3. continued)
C(17)-C(16)-C(20)
C(11)-C(17)-C(18)
C(1 1)-C(17)-C(16)
C(18)-C(17)-C(16)
C(17)-C(18)-C(19)
C(18)-C(l9)-C(20)
C(22)-C(20)-C(16)
C(22)-C(20)-C(19)
C(16)-C(20)-C(19)
C(23)-C(22)-C(20)
C(23)-C(22)-C(24)
C(20)-C(22)-C(24)

C(25)-C(24)-C(22)
C(26)-C(25)-C(24)
O(29)-C(26)-O(27)
O(29)-C(26)-C(25)
O(27)-C(26)-C(25)
C(26)-O(27)-C(28)
C(31)-O(30)-C(10)
O(32)-C(31)-O(30)
O(32)-C(31)-C(33)

O(30)-C(31)-C(33)

98

100.27(15)
118.30(15)
113.68(15)
103.84(14)
103.46(16)
107.33(15)
119.81(16)
111.70(15)
103.31(15)
113.40(16)
110.93(18)
108.11(17)
115.8(2)
113.49(19)
123.3(2)
126.0(2)
110.6(2)
115.36(19)
119.19(14)
125.12(17)
123.19(17)

111.69(15)

(Table 3. continued)
C(34)-C(33)-C(3 8) 119.81(17)
C(34)—C(33)-C(31) 122.66(16)
C(38)-C(33)-C(31) 117.5 1 (16)
C(35)-C(34)-C(33) 120.47(18)
C(34)-C(35)-C(36) 118.05(18)
C(35)-C(36)-C(37) 122.6209)
C(35)-C(36)-C(39) 118.64(19)
C(3 7)-C(36)-C(3 9) 1 18.74(18)
C(38)-C(37)-C(36) 118.58(19)
C(37)-C(38)-C(33) 120.43(18)

O(41)-C(39)-O(40) 123.9(2)
0(4 1 )-C(39)-C(3 6) 1 17.72(19)

O(40)-C(39)-C(36) 118.36(18)

 

Symmetry transformations used to generate equivalent atoms:

Table 4. Anisotropic displacement parameters (A2 x 103) for m1112404

 

U11 U22 U33 U23 U13 U12

 

0(1) 46(1) 76(1) 58(1) 12(1) 24(1) 16(1)

99

(Table 4. continued)

C(2)
C(3)
C14)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(1 1)
C(12)
C(13)
C(14)
0(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)

C(23)

38(1)
43(1)
28(1)
26(1)
32(1)
37(1)
37(1)
31(1)
25(1)
24(1)
25(1)
36(1)
32(1)
32(1)
26(1)
26(1)
35(1)
39(1)
30(1)
37(1)
33(1)

43(1)

55(1)
42(1)
31(1)
27(1)
42(1)
57(2)
34(1)
31(1)
28(1)
24(1)
27(1)
30(1)
30(1)
47(1)
27(1)
26(1)
32(1)
35(1)
33(1)
29(1)
42(1)

56(1)

30(1)
29(1)
26(1)
26(1)
32(1)
40(1)
33(1)
28(1)
29(1)
28(1)
26(1)
33(1)
30(1)
32(1)
29(1)
29(1)
38(1)
40(1)
30(1)
35(1)
30(1)

41(1)

100

13(1)
0(1)
3(1)
4(1)
6(1)
9(1)

7(1)

-2(1)

2(1)
3(1)
5(1)
0(1)

-2(1)
-3(1)
1(1)
2(1)

-1(1)
2(1)
2(1)
2(1)

1(1)

-l6(1)

11(1)

10(1)
6(1)
3(1)
6(1)
13(1)
5(1)
4(1)
4(1)
5(1)
4(1)
8(1)
5(1)
1(1)
6(1)
7(1)
13(1)
17(1)
8(1)
5(1)
9(1)
8(1)

5(1)
2(1)
0(1)
-1(1)
-9(1)
-8(1)
3(1)
-3(1)
-2(1)
1(1)
-1(1)
-7(1)
-1(1)
5(1)
4(1)
1(1)
-3(1)
2(1)
7(1)
7(1)
11(1)

6(1)

(Table 4. continued)

C(24) 60(1) 54(1) 35(1) 7(1) 19(1) 24(1)
C(25) 57(1) 67(2) 30(1) 2(1) 12(1) 20(1)
C(26) 41(1) 49(1) 39(1) -6(1) 15(1) 3(1)
0(27) 38(1) 60(1) 91(1) -35(1) 4(1) 4(1)
C(28) 44(2) 67(2) 150(3) -57(2) 4(2) 10(1)
0(29) 45(1) 66(1) 56(1) -27(1) 8(1) 3(1)
0(30) 31(1) 24(1) 36(1) 3(1) 7(1) -1(1)
C(31) 37(1) 26(1) 22(1) -3(1) 8(1) -3(1)
0(32) 36(1) 36(1) 41(1) 3(1) 7(1) -8(1)
C(33) 36(1) 27(1) 24(1) —1(1) 9(1) 0(1)
C(34) 38(1) 26(1) 37(1) 3(1) 10(1) -4(1)
C(35) 36(1) 33(1) 42(1) 0(1) 9(1) -5(1)
C(36) 40(1) 30(1) 37(1) 2(1) 9(1) 7(1)
C(37) 50(1) 27(1) 47(1) 6(1) 22(1) 0(1)
C(38) 38(1) 28(1) 40(1) 2(1) 15(1) -3(1)
C(39) 51(1) 31(1) 52(1) 4(1) 13(1) 8(1)
0(40) 41(1) 42(1) 70(1) 1(1) 7(1) 3(1)
0(41) 70(1) 54(1) 100(2) 41(1) 28(1) 21(1)

 

The anisotropic displacement factor exponent takes the form:

-2p12[h2a*2U11+...+2hka* b* u12]

101

Table 5. Hydrogen coordinates ( x 104),

. . . 2 3
lSOll'OplC dlsplacement parameters (A x 10 ),

and occupancies for m1112404

 

 

x y z U(eq) Occ.

H(3A) 3482 5639 4214 45 1
H(3B) 2673 6833 4091 45 1
H(4A) 3955 5854 5609 34 1
H(6A) 5299 8613 5977 43 1
H(6B) 6023 7405 6103 43 1
H(7A) 5106 8485 4599 53 l
H(7B) 7093 8102 5007 53 1
H(8A) 21 13 8422 4707 52 1
H(8B) 1993 9013 5512 52 1

H(8C) 604 8070 5188 52 1

H(9A) 212 6245 4927 37 1

H(9B) 1 141 5082 4989 37 1

H(10A) —521 5355 6036 33 1
H(l 1A) -38 7223 6283 30 1

H(12A) 3762 6790 6834 31 1
H(13A) 4203 8655 7099 39 1

102

 

(Table 5. continued)

lul3En
1xl4A)
rxlsA)
1u17A)
rxl8A)
rK18B)
ru19A)
IK19B)
IKZOA)
IKZlA)
luzle)
1K21C3
1K22A)
IK23A)
IK23B)
IK23C)
IK24A)
1x243)
1K25A)
IKZSB)
IK28A)

1K28B)

2108

2622

4449

1680

—1053

-2195

-982

-2440

1377

-751

-2024

-700

-1528

1156

2197

558

-1522

555

-1197

-218

-4720

-5740

8894

8919

7800

6126

5219

6281

5686

6603

6854

9135

8142

8646

8345

9384

8702

9471

6821

7003

7571

8605

10717

9602

6784

8174

8788

7689

7490

7177

8766

8447

8975

7815

7489

6969

9039

9049

9778

9880

9869

10250

11157

10885

11092

10857

103

39

37

56

32

41

41

44

44

37

50

50

50

42

70

70

70

58

58

61

61

134

134

(Table 5. continued)

H(28C) -5084 10320 10202 134
H(34A) 5181 4190 7044 40
H(35A) 7525 2993 7611 44
H(37A) 3704 804 8010 48

H(38A) 1387 1965 7391 41

 

104

10.

11.

12.

13.

14.

15.

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