mi {H lHHllHlllUilllJllf ‘ I 'UUINI'WH i ! WWI! Ml THS THESis ll‘WIllll'lllllllllllllllll 31293 01413 8972 LIBRARY Michigan State University This is to certify that the thesis entitled SYNTHESIS OF HIGHLY FUNCTIONALIZED AND STERICALLY PROTECTED PORPHYRINS presented by BAOMIN GUO has been accepted towards fulfillment of the requirements for MASTER ‘ OF SCIENCE _degree in _LHEMISIRL [Maw Major professor Date A177 6: [97; 0.7639 MS U is an Afflrmatiw Action/Equal Opportunity Institution ——————» 1 PLACE IN RETURN 80X to remove this checkom from your record. TO AVOID FINES return on or before date due. DATE DUE DATE DUE DATE DUE MSU I. An Nfinnutlve Mon/Equal Opportunlty Inetltwon mm: SYNTHESIS OF HIGHLY FUNCTIONALIZED AND STERICALLY PROTECTED PORPHYRINS BY Baomin Guo A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemistry 1996 ABSTRACT SYNTHESIS OF HIGHLY FUNCTIONALIZED AND STERICALLY PROTECTED PORPHYRINS By Baomin Guo In an effort to study proton effects on heme-bound 02, we set out to synthesize porphyrins that permit the formation of room-temperature stable metal-02 complexes in the presence of intramolecular proton donor. We discovered that xanthene-S-carboxamide can be made into excellent building blocks with which heme models having specific H-bonding at the axial ligation site can be assembled. Thus. 5-[5-carboxamide-4-(9,9-dimethyl)xanthyl]- 2,8,13,17-tetra ethyl-3,7,12,18-tetramethylporphyrin a, 5-[5-carboxhydrazide-4- (9,9-dimethyl) xanthyl]-2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrin b and their metal complexes have been synthesized. X-ray crystallographic structures of the Fe(lll) (Cl) carboxamide a and the zinc(ll) hydrazide b revealed that the xanthene oxygen atom is strongly H-bonded to one amide proton leaving the other amide proton, in the case of a, H-bonded to the CI ligand, and the hydrazide N bonded to Zn in b. In order to prevent irreversible auto-oxidation of ferrous heme, terphenyl shielding wings have incorporated to the porphyrin models. Thus, 5-(5- carboxamide-9,9-dimethyl-4-xanthyl)-15-[4-methyl~2,6-bis(4-tert-butylphenyl) phenyI]-2,8,12,18-tetraethyl-3,7,13,17-tetramethyl porphyrin c and 12,18-di[4- methyl-2,6-bis(4-tert-butylphenyl) phenyl]-5-(5-carboxamide-9,9-dimethyl-4- xanthyI)-2,3,7,8,13,17-hexamethyl porphyrin d have been synthesized. The terphenyl units were synthesized in a stepwise fashion using Pd(0)-catalyzed cross coupling of phenyl boronic acid and aryl bromide. Combining both the protective superstructure and the specific hydrogen bonding, we obtained promising models which possess a protein-like binding environment for O 2 binding and activation. To my family iii ACKNOWLEDGMENTS I would like to especially thank Dr. C. K. Chang for his great guidance throughout the various research projects as my advisor and also Dr. G. Karabatsos, Dr. K. Berglund and Dr. T. Pinnavaia for their serving as my guidance committee members. I i want to thank Dr. Rui Huang and Dr. Long Lee for their support and help on mass and NMR spectrums. Dr. S. M. Peng at National Taiwan university is appreciated for solving all the X-ray crystal structures presented in this thesis. I would also like to express my appreciation to the previous and present group members for their help, support and cooperation. They are: Dr. N. Bag, Dr. Y. Liang, Dr. S. Lee, Dr. 8. Chem, Dr. M. Sato, Ms. E. Guerin, Ms. l. M. Morrison, Mr. C. Shinner, Mr. Y. Deng, Mr. 2. Yeh and Mr. J. Kirby. With their friendship, it has always been fun for me to work in the lab. Finally I want to thank my parents and my wife for their love, support and encouragement. Baomin Guo May, 1996 TABLE OF CONTENTS Page LIST OF FIGURES ........................................................................ VI LIST OF TABLES .......................................................................... VII CHAPTER I INTRODUCTION .......................................................................... 1 CHAPTER II RESULT AND DISCUSSION .......................................................... 7 l. Functionalizing the binding site via xanthene bridge .............. 7 II. Synthesis of sterically encumbered porphyrin with meso- terphenyl shield .............................................................. 18 Ill. Synthesis of porphyrin with double terphenyl Shielding wings. 24 IV. Conclusion ..................................................................... 32 CHAPTER III EXPERIMENTAL .......................................................................... 33 REFERENCES ............................................................................ 48 LIST OF FIGURES Figure Page 1-1 Protoheme ............................................................................. 1 1-2 Schematic representation of heme protein active site ..................... 2 1-3 Single face sterically hindered porphyrins ..................................... 3 1-4 Double face sterically hindered porphyrin ..................................... 4 1-5 Distal H-bonding models ........................................................... 5 2-1 Xanthene porphyrins ................................................................ 7 2-2 X-ray structure of porphyrin 9a ................................................... 13 2-3 X-ray structure of porphyrin Iron (Ill) complex 11b .......................... 14 2-4 X-ray structure of porphyrin Zinc (II) complex 12b .......................... 15 2-5 Porphyrin with single meso-terphenyl shield .................................. 18 2-6 Porphyrin with double terphenyl shields ....................................... 24 vi LIST OF TABLES Page Table 1 Selected Bond Distances and Angles for 93 ............................ 15 Table 2 Selected Bond Distances and Angles for 11b .......................... 15 Table 3 Selected Bond Distances and Angles for 12h .......................... 17 vii Chapter I INTRODUCTION Porphyrins are important naturally occurring macrocycles that involve in many essential biological processes. Many proteins and enzymes in both animals and plants contain porphyrin-metal complexes which are the active sites of biochemical reactions”. To name a few, hemoglobin, myoglobin‘ and cytochromes5 all belong to porphyrin-containing bio-molecules. COzI‘I C02H Figure 1-1 Protoheme. Hemoglobin and myoglobin, which are essential to all mammalian life, transport and store dioxygen. The active site of these heme proteins is iron(ll) porphyrin — the heme (Figure 1-1) — embeded in a pocket and bonded to the protein through a single coordinate bond between the imidazole group of the proximal histidine residue and the iron atoms. The ferrous heme is in a five- coordinate state in the deoxy form and reversibly binds small ligand at the sixth, vacant coordinate site (figure 1-2) 7'”). In the vicinity of the heme binding site, 2 distal amino acid residues also control the binding of ligands such as CO, NO and 02 by virtue of polarity or steric effects ""5. H , , _ /<:“ Proximal side HlStldlnC H3 F8 \. *— \_N\ )1 / H3 C\ N H3 \ N ”3 c0214 COzH I-K Distal Side \N Histidine E7 Figure 1-2 Schematic representation of heme protein active site. Research of heme proteins has been focused on both the protein itself and synthetic models since the beginning. Pioneers found that an isolated heme, an iron(l|) porphyrin complex without protein pocket and distal proton, does not reversibly oxygenate and even can not resist oxidation at ordinary condition. Tremendous amounts of effort have been made to understand the chemical basis of the axial ligand and protein pocket influences on the O 2 affinity and the oxidation pathway. We now understand that a successful model of oxyhemoglobin must have a five coordinated structure and the ability to thwart irreversible oxidation pathways typically caused by the formation of u-peroxo 16-17 dimer and the presence of high proton concentration or nucleophiles at the 02 binding site. OEt Fe-Cyclophane Porphyrin Fe-Cu-cofacial Porphyrin Fe-Crowned Porphyrin Fe-Picket fence Porphrin Figure 1-3 Single face sterically hindered porphyrins Among previous approaches to study reversible dioxygen binding, there are basically two categories of models 18“9: a) superstructured heme models with steric protection on ether one side or both sides of the porphyrin resulting in room teperature stable Oz complex; b) models with distal protons that require low temperature conditions to stabilize the unprotected O 2 complex. In the superstructured heme model family, for example, we find protected porphyrins such as cyclophane porphyrin by Traylorzo, crowned porphyrin by Chang”, 22-23 ‘picket fence’ porphyrin by Collman , and cofacial porphyrin by Chang 2‘ 4 (Figure 1-3). These models built steric hindrance on one face of the heme and relied on external, often bulky, imidazoles to block the open face. There are also double face sterically hindered porphyrin models such as 25-26 ( the hanging base double bridged porphyrin by Battersby figure 1-4) which has steric protections as well as a covalently linked base to supply the proximal 0 © {Vt ©.0 0 \ i \10 figand. Figure 1-4 Hanging-base double-bridged porphyrin model Studies conducted by Chang and Traylor27 showed oxygen adducts of most Fe(ll) porphyrins are stable at low temperature because the u-peroxo dimer formation is dramatically slowed. More importantly, they also demonstrated that the Fe-Og binding affinity can be greatly enhanced by polar solvents ‘3’“. Later development in this field firmly established the fact that H-bonding at the distal side is the most influential factor that controls the O 2 binding. Several models designed to probe the distal H-bonding effect are now available. To highlight a few, naphthalene acid porphyrin and naphthalene Kemp’s acid porphyrin (Figure 1-5) are capable of providing hydrogen-bonding 28-31 interaction with the coordinated dioxygen . Unfortunately, without steric 5 protections, such hydrogen bonding models bind dioxygen reversibly only at low temperature. Naphthalene Kemp Porphyrin Figure 1-5 Distal H-bonding models Despite the fact that a large number of heme models were reported to form oxygenated heme adducts, building a realistic porphyrin model with both H- bonding effect and steric protection which forms a room teperature stable 0 2 complex in solution remains to be a challenging task. A good model, which can closely mimic the heme environment in hemoglobin as well as in other redox active cytochromes, is badly needed to serve a wide variety of research interests on heme proteins. For our research interest, we started by looking for a proper spacer group from which a distal proton can be anchored to form hydrogen bonding to the heme binding site. We also need a superstructure, which protects 6 both faces of the heme, to solidly prevent any oxidation through intermolecular dimerization. In this project, a xanthene bridge was chosen to supply a specific H-bonding possiblity. For steric protections, we developed a new terphenyl- 32’” cross coupling reaction, to ' substituted pyrrole synthesis, based on a Suzuki supply the porphyrin ring with needed steric bulk. Combining these two features, we obtained promising model compounds which have more natural protein-like binding environment and may allow us to study the chemistry of a stable heme-Oz complex. Chapter II RESULT AND DISCUSSION l. Functionalizing the Binding Site via Xanthene Bridge: In this project, we set out to introduce specific hydro gen bonding effects at the heme binding site by building novel xanthene bridged porphyrin model compounds such as a and b (Figure 2-1). FigureZ-1 Xanthene porphyrin derivatives: (a) amide, (b) hydrazide (b) Xanthene is an interesting spacer group, the oxygen atom on the middle ring of xanthene may function as a anchor which fixes the amide group right on the same plane as that of the xanthene. When incorporate into a porphyrin ring as shown in Figure 2-1, this feature allows precise positioning of a distal functional group near the porphyrin center. To synthesize such models, we started with the commercial available 9- xanthone 1 and treated it with trimethyl aluminum in toluene to give 9,9- dimethylxanthene34 2. The methlylated xanthene was reacted with butyl lithium at presence of tetramethylethylenediamine (TMEDA) and DMF to give 4,5-diformyl- 9,9-dimethylxanthene35 3 after hydrolysis (Scheme2-1). Scheme 2-1 i) BuLi/TMEDA_ ii) DMF iii) H20 The diformyl xanthene 3 was condensed with two equivalents of ethyl 3- ethyI-4-methyl-2-pyrrolecarboxylate 4 with hydrochloric acid catalyst in refluxing ethanol under argon atmosphere. The resulting formyI-dipyrrylmethane 5 was treated with hydroxylamine hydrochloride in refluxing 98% formic acid to covert the formyl group to nitrile and followed by an one-step hydrolysis and decarboxylation in refluxing ethylene glycol containing sodium hydroxide to give the alpha free dipyrrylmethane 7 (Scheme 22). 9 The xanthene dipyrrylmethane 7 was condensed36 with the diformyl dipyrrylmethane 8 in the presence of perchloric acid in dichloromethane. To facilitate purification, zinc was inserted and the resulting zinc porphyrin complex 9a could be chromatographed on silica gel. The zinc ion was removed by washing the zinc porphyrin in dichloromethane solution with 10% hydrochloric acid to give the free base porphyrin 9b. Copper could be inserted by refluxing the porphyrin 9b and copper acetate in chloroform-methanol solution (Scheme 2-3). Scheme 2-2 CHO CHO Z—f COzEt + 2cq. CO Er N 2 NH H HCI/EtOH CH COzEt NHZOH-HCL N" NaOH ncozn C” (CHon')2 NH 6 C023 10 Scheme 23 OHC ii) o-chloranil i) Perchloric Acid I iii) Zn++ 9a M=Zn(II) H+ 9b M=2H : 9c M: 01(11):: CU(OAC)2 X-ray crystallography of the porphyrin-xanthene-acid zinc(|l) complex 93 (Figure 22) showed that the acid proton was attached to the xanthene oxygen and was unavailable to form hydrogen-bonding with ligand at the porphyrin metal center. 11 Scheme 2-4 12a lla ZIKOACh I) FCBI’z ii) NaOH iii) HCl C) Cr i) \ j‘ (: /N\N/H N‘H... 1 ........ 0"“ .‘ ---------- 0"” j: W . \ \ N\ r N ~ N\ N -- © zn\N G F\ \_ / / \ In order to explore a hydrogen-bonding possibility to heme-bound substrates, we converted 9b to the carboxamide porphyrin 113, by first converting the acid to an acid chloride 10 using thionyl chloride, then reacting 17 H with ammonia gas in dichloromethane. Similarly, we also obtained the porphyrin carboxhydrazide 123 by reacting the porphyrin acid chloride 10 with anhydrous hydrazine (Scheme 2-4). The X-ray structure of the hemin chloride 11b (Figure 2-3) indeed showed the expected hydrogen bonding with the axial ligand. The X-ray structure of 12b (Figure 2-4), however, showed tat the terminal hydrazide nitrogen formed a nitrogen-zinc bond which both blocked the distal side of porphyrin complex and pulled the xanthene bridge toward the porphyrin ring. Coordination between iron and SP3-nitrogen is typically very weak, it occurs in this system undoubtedly because of the steric constraints brought by the unique arrangement. Fi ure 2-2 X-ray structure of zinc carboxylic acid porphyrin complex 9a m8 §m l‘ as no» 14 Figure 2-3 X-ray structure of iron carboxamide porphyrin complex 11b 032 H m L) lllll N [-I :8 "‘If"' F e o " N K74 I m S N 5 it: 8 3 8 "“3 {‘1’ t.) ‘ III/A 15 Table 1. Selected Bond Distances and Angles for 9a Distance (A) (ESD) Angle (degree) (ESD) Zn-O1 2.250 (14) O1-Zn-N1 99.5 (4) Zn-N1 2.055 (13) Of—Zn-N1 99.5 (4) Zn-Nf 2.055 (13) O1-Zn-N2 94.7 (5) Zn-N2 2.053 (14) O1-Zn-N2 94.7 (5) Zn-N2 2.053 (14) Zn-O1-Ho1a 122.3 (13) 01-H01 a 0.955 (15) Zn-O1-Ho1b 120.0 (11) O1 -Ho1 b 0.960 (17) C23-O2-Ho4 97.7 (15) 02-Ho4 1.584 (18) 026-04-Ho1 a 117.7 (16) O4-Ho1 a 1.888 (19) C26-O4-Ho4 99.2 (17) O4-Ho4 0.969 (20) ' Table 2. Selected Bond Distances and Angles for 11b Angle (degree) (ESD) Fe-Cl Fe-N1 Fe-N1 Fe-N2 Fe-N2 CI-Hf O1-H2 02-026 N3-C26 N3-H1 N3-H2 Cl-Fe-Nf CI-Fe-Nf CI-FerN2 Cl-Fe-N2 Fe-Cl-H1 024-01 -H2 026-N3-H1 026-N3-H2 H1 -N3-H2 106.72 (12) 106.72 (12) 99.27 (13) 99.27 (13) 110.12 (10) 103.9 (5) 106.5 (7) 116.7 (8) 136.8 (9) 16 Fi ure 2-4 X-ray structure of zinc carboxhydrazide porphyrin complex 12b p \ «w. } fii l V 3.... .4! 7n 81 muwva v ‘0 no 8% 8 «.5 m‘ AWN no g ..,8 emu 93v O 03 $2. mz u \. ‘ 3RD, 11.“.1.\ 1V 111 mo 08/ ,5' N8 8:? 1‘. 17 Table 3. Selected Bond Distances and Angles for 12b Distance(A ) ESD) Angle (degree) (ESD) Zn-N1 Zn-N2 Zn-N3 Zn-N4 Zn-N5 02-036 N5-N6 N6-036 ( 2 029 (7) 2 031 (8) 2. 075 (7) 2. 024 (8) 2 247 (9) 1.298(15) 1408(14) 1. 278 (17) N5-Zn—N1 N5-Zn-N2 N5-Zn-N3 N5—Zn-N4 Zn-N5-N6 N5-N6-C36 02-C36-N6 C1 -C20-C21 019-020-021 C20-CZ1-035 91.6 (3) 100.4 (3) 104.6 (3) 96.5 (3) 117.4 (6) 124.6 (9) 115.4 (13) 120.2 (9) 119.5 (9) 117.1 (9) 18 II. Synthesis of Sterically Encumbered Porphyrin with single meso- Terphenyl Shield: A preliminary dioxygen binding study, conducted by our group member, indicated that the carboxamide heme 11b auto-oxidized rapidly in solution. To help stabilize the O2 adduct, we designed a terphenyl “picket fence” substituted at a single meso position of the carboxamide xanthene porphyrin. In theory, this sterically hindered model (0) should retard the heme-Oz oxidation process (Figure2-5). Figure 2-5 Porphyrin with single meso-terphenyl shield In traditional porphyrin synthesis, mesa-substituted porphyrins are made by direct condensation of benzaldehyde and pyrrole. Such reactions do not work very well with highly crowded benzaldehyde. Therefor, a new strategy has been developed to build the terphenyl wing by using Pd 0 catalyzed cross- coupling between aryl boronic acids and bromobenzene (the Suzuki ”'33 Coupling). 19 The synthesis of the meso substituted porphyrin (c) began from the commercially available 2,6-dibromo-4-methylaniline 13. The aniline 13 was first carefully treated with a nitrosyl sulfuric acid solution at room temperature, then followed by substitution of cyanide with KCN/CuCN at 0 °C. The crude 2,6- dibromo-4-methylbenzonitrile 14 product was purified by flash chromatography on silica gel column. The benzonitrile 14 was then reduced by diisobutyl aluminum hydride (DIBAL) to give 2,6-dibromo-4-methylbenzaldehyde 15. All reactions were smooth and in good yield under careful handling (Scheme 25). Scheme 2-5 H3 H3 3 i) NaNOyjHZSO4 ii) KCMNMCCE DIBAl-H Br Br Br Br Br Br NHz CN CHO 13 14 15 The condensation of the benzaldehyde 15 with ethyl 3-ethyl-4-methyl-2- pyrrolecarboxylate 4 was first carried in refluxing ethanol with HCI catalyst, but yield was less satisfactory. So we turned to condense them in dichloromethane in presence of titanium tetrachloride 37 under argon atmosphere. The resulting dipyrrylmethane 16 was purified on silica gel column by chromatography with dichloromethane as eluent containing a trace amount of triethylamine. When we tried to carry out the hydrolysis and decarboxylation in one step by refluxing it overnight in a solution of NaOH, water and ethanol, the dipyrrylmethane severely decomposed. So we employed a two-step method, which gave decent yields. The dipyrrylmethane 16 was first hydrolyzed with 20% sodium hydroxide in refluxing ethanol for 3 hours, then melted with a 1:1 mixture of potassium acetate and sodium acetate trihydrade at 160 °C under argon atmosphere. The 20 crystalline alpha free dipyrromethane 17 was obtained by filtration in almost quantitative yield after salts was washed out (Scheme 26). Scheme 26 + 2 C023 . H3C N T1 C14 Br Br H —> CHO 15 4 NaOAc-3HzO H3C KOAc The dipyrrylmethane 18 was further converted to diformyl dipyrryl methane 19 with POCI3 and DMF”. The crude diformyl dipyrrylmethane 19 was used to couple with the xanthene dipyrrylmethane 7 in the presence of p- toluenesulfonic acid followed by air oxidation facilitated with zinc acetate and sodium acetate to give the porphyrin 20. The acid porphyrin 20 was carefully purified on silica gel column by chromatography (Scheme 27). Before replacing the bromo group of 20 with 4-t-butylphenyl, we decided to converted it to carboxamide porphyrin 21 first. The porphyrin 20 was reacted 71 with thionyl chloride in refluxing dry dichloromethane for 1 hour before the excess reagent and solvent were pumped dry. After the acid chloride was re- dissolved in dry dichloromethane, ammonia gas was passed through the solution. The resultant product is a pure single compound—porphyrin carboxamide 21 in quantitative yield. This amide was then heated with 10 equivalents of 4-t-butylphenyl boronic acid 38 in the presence of Pd(PPh3)4 catalyst in DMF under argon atmosphere to give the terphenyl shielded porphyrin 22a (Scheme 28). The excessive amount of boronic acid seems advantageous. An early run of this coupling with 3 equivalents of boronic acid and less palladium catalyst showed an incomplete reaction. 22 Scheme 27 i) Pooh/0M}; ii) Base H3C 23 Scheme 28 Pd(PPh3)4, NaCO3 4-t-Bu-PhB(OH)2,DMF 22 a) M: 2H Com: b) M=Co(ll) 24 Ill. Synthesis of Porphyrin with Double Terphenyl Shielding Wings: To further protect the porphyrin metal center, we designed and synthesized the porphyrin (1 (Figure 2-6). The porphyrin d has two terphenyl shields on the beta-pyrrole positions in addition to a xanthene amide at meso position. As the two rather large shields are totally blocking the metal center, this model may give a stable metal porphyrin oxygen complex and provided us a chance to study chemical reaction with the heme-Oz complex at manageable conditions where most previous models failed to survive. Figure 2-6 Porphyrin with double terphenyl shields For synthesis, the key building block is the 3-terphenyl pyrrole 27. We started to make 27 from 2,6-dibromo-4-methylbenzaldehyde 15. A mixture of aldehyde 15 and NH4OAc was brought to reflux in excess nitroethane to yield the nitropropene 24 in 95% yield after removal of the excess nitroethane and chromatography. 24 was then reacted with isocyanoacetate 25 in dry THF in presence of two equivalents of DBU at room temperature. After 24hr the reaction mixture was poured into 10% HCI to precipitate the dibromo aryl pyrrole 26. The precipitate was collected by filtration and purified on silica gel column to 25 give a pure dibromo pyrrole40 26 in 62% yield. The dibromo pyrrole 26 was coupled with 4- t-butylphenyl boronic acid to give the terphenyl pyrrole 27 in 66% yield as light yellow solid after flash chromatography (Scheme 2-9). Scheme 2-9 H3 CZHSNOZ > H Br Br NH4 CH3C02 H0 15 24 CNCHZCOZCHzPh 25 DBU 8‘ Pd(PPIb)4 4—r-Bu-Phenyl Boronic Acid Br / \ 26 H The pyrrole 27was reacted with methylal in refluxing chloroform in the presence of p-toluenesulfonic acid (PTSA) under argon atmosphere for 18hr and the solution was extracted with dichloromethane. After purification on silica gel column, the dipyrrylmethane 28 was obtained in 57% yield. The dipyrryl methane benzyl ester 28 was hydrogenolized in methanol with Pd-C(10%) catalyst to give the dipyrrylmethane di-acid 29 in 96% yield. The di-acid 29 was then decarboxylated in refluxing ethanolamine under argon atmosphere for 30 min to yield the alpha free dipyrrylmethane 30 in 91%. It was further reacted 26 with POCI3 and dry DMF to give formyl dipyrrylmethane 31, after hydrolysis (Scheme 2—10). The formyl dipyrrylmethane 31 was directly used for following reactions without purification. Scheme 2-10 Ar Ar 2 ——~§$§§.OC“3” H H H 27 H2 / Pd Ar r Ar HzNCHzCHzOH H 30 H H 29 H i) POCI3, DMF ii) NazCO3 ©©© CHO :22 31 In an attempt to make our desired diaryl porphyrin d, we first condensed the formyl dipyrrylmethane 31 with a simple alpha free dipyrrylmethane 32. In normal MacDonald condensation condition, the yield of the diaryl porphyrin 33 is reasonable—8%. But it did not work when we tried to couple 31 with the xanthene dipyrrylmethane 7. The terphenyl substituent may be too big a steric hindrance during the coupling (Scheme 2-11). To look for an alternative synthetic approach, we turned to a method based on tetrapyrrole biting down an aromatic aldehyde. In order to test if 27 diformyl xanthene 3 would work in tetrapyrrole condensation, we refluxed a methanol solution of unshielded tetrapyrrole 34 and 3 in presence of a few drops of HBr/acetic acid (30%) under argon for 24hr. The reaction gave an excellent yield (35%) of the aldehyde porphyrin 35 (Scheme 2-12). Scheme 2-11 This result suggested that this approach to our desired porphyrin d may be feasible. We chose to use 3,4-dimethylpyrrole 36 to make tetrapyrrole because the two relatively small methyl groups on beta positions can further reduce steric effect in both the tetrapyrrole formation and the porphyrin cyclization. The diaryl tetrapyrrole 37 was obtained by reacting dimethylpyrrole 36 with formyl dipyrrylmethane 31 in methanol containing HBr (48% aq.). After 28 the mixture was heated on steam bath for 3 min followed by standing at room temperature for 2 hr, it was cooled in a refrigerator to help precipitate the product. The brown diaryl tetrapyrrole 37 was collected by filtration and washed with methanol containing a small amount of HBr. It was used for next step without further purification (Scheme 2-13). Scheme 212 N N N N H H+ H+ H 28r- 34 lHBr/CH3C02H The tetrapyrrole 37 was coupled with diformyl xanthene 3 in refluxing methanol in presence of a few drops of HBr/acetic acid (30%) for 24hr. The major compound we got is the desired xanthene diaryl porphyrin 38. The porphyrin 38 was carefully purified on silica gel by chromatography (Scheme 2- 14). 29 Scheme 2- 13 36 31 HBr/HzO CH3OH Ar r N N N N H H+ H)r H ZBr- 37 Scheme 2-14 Ar N N N H H+ H+ 2Br' 37 HBr/CH3C02H CHO CH3OH ooooooooo 21:2 3O Converting the aldehyde group to nitrile 39 was achieved by refluxing 38 with excess NHzOHoHCl in formic acid overnight under argon atmosphere. The hydrolysis of the nitrile to carboxylic acid was proved to be troublesome. We first tried to reflux it with formic acid, HCI and 20% water for a day, but it did not give any hydrolyzed product. We then turned to alkaline hydrolysis. A mixture of porphyrin, NaOH, Pyridine and 10% water was refluxed for 24 hours, but only a trace amount of hydrolyzed product was detected on TLC. It seems a stronger condition was needed. The hydrolysis was finally successful when porphyrin 39 was refluxed with a large excess of NaOH in pure ethylene glycol at 198 °C for 1 day under argon atmosphere. The product—porphyrin 40 was purified on silica gel plate with dichloromethane containing 2% methanol as the eluent. The amide porphyrin 42 was obtained following the regular acid chloride-anhydrous ammonia route. Cobalt complexes of both 22a and 43 were prepared and they will be used for 02 binding study. To avoid the troublesome hydrolysis of 39, we developed an alternative method to convert the porphyrin 38 to acid 40 directly by oxidation. While many conventional oxidation methods are available in converting aldehyde to acid, few has been applied to porphyrinic aldehyde. The oxidation condition proved to be tricky since degradation of the porphyrin often occured. However, we discovered that the best condition is the Jone's reagent in ice bath for 1.5 hr and then followed by room temperature for 1.5 hr under argon atmosphere. This gave us the optimum yield on converting porphyrin 38 to 40 in one step without the going through the difficult cyanide hydrolysis. 31 Scheme 2-15 32 IV. Conclusion: In this research, we have demonstrated the effectiveness of a xanthene amide group as an intramolecular proton donor in heme models. When incorporated onto a porphyrin meso position, the xanthene oxygen bridge uniquely anchors one amide proton and renders the other amide proton pointing toward the porphyrin metal center. As such, it may serve as an excellent model for the distal H-bonding effect in heme enzymes. Replacing the amide by a hydrazide group, however, resulted in a stable metal-to-hydrazido nitrogen bond. We have also explored new strategies of introducing steric shielding to heme model compounds. We have synthesized shielded porphyrins with either a single meso attached or two beta-connected terphenyl groups having further substituents at the flanking wings of the terphenyl. These exceedingly bulky superstmctures were made through the use of Suzuki cross-coupling reactions. The combination of intramolecular proton donor (from xanthene amide) and steric protections should allow the realization of stable heme-dioxygen complex even at room temperature. Chapter III EXPERIMENTAL Materials and measurements Reagents and solvents for synthesis were used as received unless otherwise stated. 1H NMR spectra were recorded on Varian Gemini-300 in 99.9% CDCI3 with residual CHCI3 as the internal standard set at 7.24 ppm. Mass spectra were measured on a VG Trio-1 mass spectrometer for M/Z less than 1000 or on JEOL HX-110 HF double focusing spectrometer in the FAB-MS positive ion detection mode for M/Z over 1000. UV- Visible spectra were measured on a Shimadzu 160 spectrometer. Infrared spectra were measured on a Nicolet IR/42 spectrometer. 4,5-DIformyl-9,9-dlmethylxanthene (3): 9,9-Dimethylxanthene (3 g, 14 mmol) and tetramethylethylenediamine (TMEDA) (5.72 ml) in dry heptane (150 ml) was degassed by passing argon through for 5 min. To this solution butyl lithium (21.45 ml,1.6 M hexane solution) was added dropwise in a 30 min period, this resulting solution was refluxed for 10 min and cooled to 0 °C. After dry DMF (6 ml) was added, the solution was slowly warmed up to room temperature and stirred for 15 min. The solution was poured into water (500 ml), and the precipitated product 3 was collected by filtration. Yield: 80%. MS: m/z = 266.0 for C17H1403, ‘H NMR (300 MHz, CDCI3): 6: 10.69 (2H, s, C_l-_I_O), 7.82 (2H, d), 7.71 (2H, d), 7.21 (2H, d), 1.71 (6H, s). 5-FormyI-4-[[5,5’-bis(ethoxycarbonyl)-4,4’-diethyl-3,3’-dimethyl-2,2’- dipyrryl]methyl]-(9,9-dimethyl)xanthene(5): 4,5-DiformyI-9,9- dimethylxanthene (522 mg, 2 mmol) was dissolved in anhydrous ethanol (20 ml) at room temperature in presence of concentrated HCI (0.5 ml) under argon 33 34 atmosphere. To this solution was added ethyl 3-ethyI-4-methyl-2-pyrrole carboxylate (742 mg, 4.1 mmol) in three portions over a period of 15 min. The solution mixture was refluxed for 45 min under argon atmosphere. The deep colored solution was then kept in refrigerator for 4 h and the light yellow crystalline solid was collected by filtration. The filtrate was concentrated and then diluted with water. The solid product was filtered and thoroughly washed with water to give yellow crystals of 5. The combined yield was 987 mg (81%) : mp 104-106 00; MS: m/z = 610 for c,,H,2Nzo,; ‘H NMR (300 MHz, CDCIa): 6 = 10.12 (1H, s, CH0), 8.30 (2H, br, NH), 7.65 (2H, t), 7.39 (1H, d), 7.17-7.06 (2H, m), 6.79 (1H, d), 5.99 (1 H, s, methane CH), 4.21 (4H, q), 2.69 (4H, q), 1.80 (6H, s), 1.64 (6H, s), 1.26 (6H, t), 1.08 (6H, t). 5-Cyano-4-[[5,5’-bis(ethoxycarbonyI)-4,4’-diehyl-3,3’-dimethyl-2,2’- dipyrryl]methyl]-(9,9-dimethyl)xanthene (6): The aldehyde 5 (610 mg, 1 mmol) was dissolved in 99% formic acid (8 ml) and hydroxylamine hydrochloride (75 mg, 1.1 mmol) was added to the mixture. The resulting mixture was refluxed for 1 h before being poured onto ice. After the solution was neutralized with 5% NaOH solution, the brown solid was collected by filtration to afford 590 mg (97%) of 6. MS: m/z = 607.4 for c,,H,,N,os; IR VON 2236 cm", ‘H NMR (300 MHz, 0001,): 6: 8.19 (2H, br, NH), 7.66-7.51 (2H, m), 7.40 (1H, CI), 7.27-6.95 (2H, m), 6.68 (1H, d), 5.70 (1 H, s, methane CH), 4.22 (4H, q), 2.70 (4H, q), 1.81(6H, s), 1.54 (6H, s), 1.28 (6H, t), 1.07 (6H, t). 5-[5-Carboxylic acid-4-(9,9-dimethyl)xanthyl]-2,8,13,17-tetraethyI-3,7,12,18- tetramethylpophinato Zinc(ll) (93): The diester dipyrrylmethane 6 (500 mg, 0.82 mmol) was decarboxylated and the cyano group was simultaneously hydrolyzed by refluxing for overnight in ethylene glycol (20 ml) containing NaOH solution (5 ml, 20%) at argon atmosphere. The dark color solution was poured into ice water and the resulting yellowish-brown solid was collected by filtration. 35 This decarboxylated dipyrrylmethane 7 and 5,5'-diformyl-3,3’-diethyl-4,4’- dimethyl-2,2’-dipyrrylmethane (230 mg, 0.81 mmol) was dissolved in dry methanol (60 ml) under argon atmosphere. To this mixture 70% perchloric acid (0.5 ml) was added and the solution was stirred at room temperature under argon atmosphere with exclusion of light for 16 h. Then a solution of NaOAc (0.5 g) in methanol (10 ml) was added, followed by another solution of o-chloranil (180 mg) in methanol (5 ml). After 1 h, the solvent was removed and the residue was taken up in dichloromethane (20 ml) and a solution of zinc acetate (300 mg) in methanol (5 ml) was added. After being stirred for 3 h, the solvent was evaporated and the residue was purified by chromatography (silica gel, dichloromethane) to give 182 mg (29%) pure product of 93. UV-Vis (dichloromethane): it max.(rel. int.) = 406 (0.668), 536 (0.033), 570 (0.032); MS: m/z= 792.7 for C48H48N4032n; 1H NMR (300 MHz, CDCI3): 6: 10.15 (2H, s, meso), 10.06 (1H, s, meso), 7.93 (2H, m), 7.72-7.58 (3H, m), 7.08 (1H, t), 4.09 (8H, q), 3.65 (6H, s), 2.50 (6H, s), 1.94 (12H, m), 1.76 (6H, t). 5-[5-Carboxylic acid-4-(9,9-dimethyl)xanthyI]-2,8,13,17-tetraethyl-3,7,12,18- tetramethylporphyrin (9b): The Zinc porphyrin 9a was demetalated by washing with 10% HCI in dichloromethane to afford 9b in quantitative yield. UV- Vis (dichloromethane): km... (rel. int.) = 403 (0.868), 501 (0.114), 534 (0.070), 571 (0.053), 622 (0.022); MS: m/z = 730.5 for 6,,H50N,o,; ‘H NMR (300 MHz, CDCI3): 8: 10.14 (2H, s, meso), 9.96 (1 H, s, meso), 7.93 (1H, d), 7.78(1H, d), 7.71 (1H, d), 7.64 (1H, d), 7.59 (1 H, t), 7.11 (1 H, t), 4.08-3.92 (8H, m), 3.62 (6H, s), 2.47 (6H, s), 1.93 (6H, s), 1.86 (6H, t), 1.71 (6H, t), -3.26 (2H, br, NH). 5-[5-Carboxylic acid-4-(9,9-dimethyl)xanthyI]-2,8,13,17-tetraethyI-3,7,12,18- tetramethylpophinato Copper(ll) (90): A mixture of porphyrin 9b (25 mg, 0.03 mmol) in chloroform (20 ml) and copper acetate (80 mg, 0.4 mmol) in methanol (5 ml) was refluxed for 45 min before the solvent was removed. The residue was 36 dissolved in dichloromethane and the crude product was chromatographed on silica gel eluting with dichloromethane to give 26 mg (96%) of 9c. UV-Vis (dichloromethane): Max. (rel. int.) = 402 (1.035), 527 (0.043), 564 (0.061), MS: m/z = 790.9 for C48H48N403Cu. 5-[5-Carboxamide-4-(9,9-dimethyl)xanthyl]-2,8,13,17-tetraethyl-3,7,12,18- tetramethylporphyrin (113): To porphyrin 9b (25 mg, 0.03 mmol) in dry dichloromethane (10 ml) was added SOCI2 (0.5 ml) and the solution was refluxed for 1 h under argon atmosphere before the solvent was removed. The residue was dissolved in dry dichloromethane and NH3 gas was bubbled through the solution for 2 min. The solution was washed with water and evaporated to afford a purple solid of 11a (25 mg, 98%). UV-Vis (dichloromethane): it max. (rel. int.) = 402 (1.134), 502 (0.119), 535 (0.071 ), 570 (0.066), 623 (0.038); MS: m/z = 729.5 for C 48H51NSOZ; 1H NMR (300 MHz, 00013): 6: 10.16 (2H, s, meso), 10.00 (1 H, s, meso), 7.94-7.88 (2H, m), 7.65- 7.57 (3H, m), 7.03 (1 H, t), 4.29 (2H, br, amide NH) 4.12-3.93 (8H, m), 3.64 (6H, s), 2.51 (6H, s), 1.90 (6H, s), 1.85 (6H, t),.1.72 (6H, t), -3.24 (2H, br, NH). 5-[5-Carboxamide-4-(9,9-dimethyl)xanthyl]-2,8,13,17-tetra ethyl-3,7,12,18- tetramethylporphinato Iron(lll) chloride (11b): Iron was inserted into the porphyrin core 113 by the usual FeSO4 method. UV-Vis (dichloromethane): Max_(rel. int.) = 385 (0.928), 503 (0.088), 534 (0.077), 639 (0.036); MS: m/z = 783.1 [M+ - 01] for 0,,H,,N50201Fe. 5-[5-Carboxhydrazide-4-(9,9-dimethyl)xanthene]-2,8,13,17-tetraethyl- 3,7,12,18-tetramethylporphyrin (123): To porphyrin 93 (25 mg, 0.03 mmol) in dry dichloromethane (10 ml) was added SOCI2 (0.5 ml) and the solution was refluxed for 1 h under argon atmosphere before the solvent was removed. The residue was dissolved in dry dichloromethane and an excess of anhydrous 37 hydrazine (10 ml, 0.29 mmol) was added. The solution was stirred for 10 min before being washed with water. The solvent was evaporated to afford a purple solid (25 mg, 98%) of 12a. UV-Vis (dichloromethane): A max, (rel. int.) = 404 (1.003), 503 (0.082), 536 (0.045), 570 (0.044), 623 (0.019); MS: m/z = 744.2 for 0,,H52N602; 1H NMR (300 MHz, 00013): 6: 10.17 (2H, s, meso), 9.99 (1H, s, meso), 7.93 (2H, d), 7.59 (3H, m), 7.05 (1 H, t), 5.23 (1 H, br, hydrazide NH) 4.04 (8H, m), 3.64 (6H, s), 2.49 (6H, s), 1.89 (6H, s), 1.88 (6H, t), 1.73 (6H, t), -0.91 (2H, hydrazide NH), -3.18 (1 H, br, NH), -3.23 (1 H, br, NH). 5-[5-C3rboxhydrazide-4-(9,9-dimethyl)xanthyI]-2,8,13,17-tetraethyl- 3,7,12,18-tetramethylporphinato Zinc(II) (120): A mixture of porphyrin 123 (25 mg, 0.03 mmol) in chloroform (20 ml) and zinc acetate (75 mg, 0.34 mmol) in methanol (5 ml) was refluxed for 45 min before being washed with water. The solvent was evaporated to give 26.5 mg (98%) of 12b. UV-Vis (dichloromethane): it max.(reI. int.) = 415 (1.055), 543 (0.056), 580 (0.033); MS: m/z = 808.1 for 0,,H50N6022n; 1H NMR (300 MHz, 00013): 6 = 10.06 (2H, s, meso), 10.01 (1H, s, meso), 8.69 (1H, d), 7.85 (1H, d), 7.71 (1H, t), 7.35 (1H, d), 7.03 (1H, d), 6.70 (1 H, t), 4.10 (6H, m), 3.85 (2H, q), 3.62 (6H, s), 2.56 (6H, s), 2.48 (1H, br, hydrazide NH), 1.91 (6H, t), 1.74 (6H, s), 1.73 (6H, t), -1.91 (2H, br, hydrazide NH). 2,6—Dibromo—4-methylbenzonitrile (14): Sodium nitrite (75.9 mg, 11 mmol) was added portionwise to a stirred concentrated sulfuric acid (10 g) at 0 °C. The resulting solution was allowed to warm up to 55 °C and then held at room temperature for 15 min. This nitrosyl sulfuric acid solution was then added dropwise to a stirred solution of 2,6-dibromo-4-methylaniline (2.65 g) in acetic acid (10 ml) at 20 °C. After standing 1 h at room temperature, the diazonium solution was carefully added to a vigorously stirred 100 ml aqueous solution of KCN (3.7 g, 55 mmol), CuCN (1.35 g, 15 mmol) and NazCoa (12.7 g, 120 mmol) 38 at 0 °C. After completing the addition, the resulting mixture was stirred at room temperature for 1 h. The crude product was precipitated, filtered, thoroughly washed with water and dried. This crude product was dissolved in benzene and the insoluble inorganic material was removed by filtration. The filtrate was chromatographed (silica gel, hexane-dichloromethane) to give benzonitrile 14 as light yellow solid (2.29 g, 83.3%) . mp:149-150°C. MS, m/z =274.8 for CaHsBer. ‘H NMR (300 MHz, 0001.): 6:237 (3H, s), 7.44 (2H, s). 2,6-DIbromo-4-methyI-benzaIdehyde (15): 2,6-dibromo-4-methyl- benzonitrile 14 (2.75 g, 10 mmol) in dry heptane (20ml) was dissolved at 0 °C under argon atmosphere. To this solution diisobutyl aluminum hydride (DIBAL) (12 ml, 12mmol,1 M hexane solution) was added dropwise, and the resulting solution was stirred at 0°C for 30 min, at room temperature for 2 h, and then was refluxed for 5min. After cooled to room temperature, this solution was poured into HCI (60 ml, 6 N) with crushed ice. After stirred for 1 h, the mixture was extracted with dichloromethane (50 ml x 2). The organic layer was combined, washed with saturated aqueous NaHC03 solution, and concentrated. The residue was chromatographed (silica gel, hexane-dichloromethane) to give light yellow solid benzaldehyde 15 (1.57 g, 56.7%). mp:96-97 °C. MS, m/z =277.9 for CeHeBI’zO. 1H NMR (300 MHz, CDCI3): 6:2.35 (3H, s), 7.45 (2H, 5), 10.22 (1H, s). 2,6-DIbromo-1-[[5,5’-bis(ethoxycarbonyl)-4,4’-diethyl-3,3’-dimethyl-2,2’- dipyrryl]methyll-4-methylbenzene (16): 15 (1.0 g, 3.6 mmol) and ethyl 3- ethyI-4-methyl-2-pyrrolecarboxylate (1.3 g, 7.2 mmol) in dry dichloromethane (100 ml) was degassed by passing argon through for 15 min. After TiCl 4 (1.5 ml) was added, the resulting solution was stirred for 24 h at room temperature. The reaction solution was thoroughly washed with water and chromatographed (silica gel, dichloromethane) to afford light yellow solid 16 (2.0 g, 89%). MS, m/z =622.1forCzeH34NzBr2. 1H NMR (300 MHz, 00013): 8: 1.15 (6H, t), 1.31 (6H, t), 39 1.77 (6H, s), 2.30 (3H, s), 2.65-2.69 (4H, m), 4.23-4.34 (4H, m), 6.31 (1H,s, methane CH), 7.43 (2H, s), 7.76(2H, br). 2,6-Dibromo-1-[[4,4’-diethyl-3,3’-dimethyl-2,2’-dipyrryl]methyI]-4-methyl benzene (18): 16 (1.0 g, 1.6 mmol), NaOH (1.0 g in 5 ml water) and ethanol (15 ml) were refluxed for 3 h under argon atmosphere. After it was cooled to room temperature, the reaction solution was poured into ice water (50 ml) and neutralized withf 0% HCI to give pink solid 17 (0.90 g, 99%). The diacid 17 was mixed with NaOAc:3H20 (5 g) and KOAc (Sg), heated to melt at 160 °C under argon atmosphere, and then cooled to room temperature. To the reaction mixture water (50ml) was added, and the yellow precipitate was filtered, washed with water to give 18 (0.68 g, 81%). MS, m/z=478.1 for szstNzBrz. 1H NMR (300 MHz, CDCI3): 5: 1.16 (6H, t), 1.78 (6H, s), 2.26 3H, s), 2.41 (4H, q), 6.33 (1H, s, methane CH), 6.40 (2H, d, a-H), 7.39 (2H, s), 7.76 (2H, s). 2,6-DIbromo-1-[[5,5’-diformyI-4,4’-diethyI-3,3’-dimethyl-2,2’-dipyrryl]methyl]- 4-methylbenzene (19): To a solution of 18 (1 g, 2.1 mmol) in dry DMF (7 ml) emersed in an ice bath was added POCI3 (0.5 ml) in ice bath and the resulting solution was stirred for 10 min in ice bath and held at room temperature for 2 h. After the excess DMF was removed, the residue was hydrolyzed with saturated sodium carbonate aqueous solution at 60°C for 5 min. The yellow precipitate was collected by filtration, washed thoroughly with water and gave crude product 19 (1g). 19 was used directly for the following step without further purification. MS, m/z=534.2 for C24H26N202Br2. 5-(5-Carboxyllc acid-9,9-dimethyl-4-x3nthyl)- 15-(4-MethyI-2,6-dibromo phenyI)-2,8,12,18-tetraethyI-3,7,13,17-tetramethylporphyrin (20): Formyl dipyrrylmethane 19 (267 mg, 0.5 mmol) and dipyrrylmethane 7 (241 mg, 0.5 mmol) were dissolved in dichloromethane (150 ml). To this solution, p- toluenesulfonic acid (475 mg, 2.5 mmol) in methanol (5 ml) was added. The 40 resulting solution was stirred for 12 h, before a solution of Zn(OAc) 2 (200 mg) and NaOAc (800 mg) in methanol (15 ml) was added and stirred overnight. After the solution was washed with water (100 ml), HCI (50 ml, 10%), and water (100 ml), it was dried with sodium sulfate and concentrated. Porphyrin 20 was chromatographed (silica gel, methanol-dichloromethane). Yield: 48 mg (10%). MS, m/z = 978.8 for C55H54Br203N4. 5-(5-Carboxamide-9,9-dimethyl-4-xanthyl)- 15-(4-MethyI-2,6-dibromo phenyl)-2,8,1 2,1 8—tetr3ethyI-3,7,1 3,17-tetramethylporphyrln (21): To a solution of porphyrin 20 (25 mg, 0.03 mmol) in dry dichloromethane (10 ml) was added SOCI2 (0.5 ml) and this resulting solution was refluxed for 1 h under argon atmosphere before the solvent was removed. The residue was dissolved in dry dichloromethane and NH3 gas was bubbled through the solution for 2 min. The solution was washed with water and evaporated to afford a purple color solid of porphyrin 21 (25 mg, 98%). MS: m/z = 977.6 for C55H55N502BI’2; 1H NMR (300 MHz, CDCI3): 5: 10.21 (2H, s, meso), 7.94784 (2H, m), 7.65-7.57 (3H, m), 7.03 (1H, t), 4.45 (2H, br, amide NH) 4.12-3.93 (8H, m), 2.68 (3H, s), 2.63(6H,s), 2.52 (6H, s), 1.91 (6H, s), 1.80 (6H, t),.1.72 (6H, t), 1.54 (6H,s), -2.40 (2H, br, NH). 5-(5-Carboxamide-9,9-dimethyl-4-xanthyI)-15-[4-methyI-2,6-bis(4- tert- butylphenyl)phenyl]-2,8,12,18-tetraethyl-3,7,13,17-tetramethylporphyrin (223): Porphyrin 21 (30mg, 0.031 mmol) was dissolved in DMF (5 ml) and was degassed by passing argon through the solution for 15 min. To this solution, Pd(PPh3)4 (30 mg) was added and followed by sodium carbonate (30 mg in a minimum amount of water) and 4-fert-butylphenyl boronic acid (88 mg). The mixture was refluxed for 48hr under argon atmosphere before it was diluted with dichloromethane (30 ml) and washed with water. The dichloromethane solution was then dried with sodium sulfate and concentrated and the residue was chromatographed (silica gel plate, 1% methanol in dichloromethane) to give 41 purple solid porphyrin 22 (18 mg, 54%) . UV-Vis (dichloromethane): A max, (rel. int.) = 412.5 (2.147), 510.5 (0.205), 543.5 (0.105), 578.5 (0.138), 629.0 (0.072). MS: m/z = 1083.6390 for C75H31N502. 1H NMR (300 MHz, CDCI3): 5: 10.06 (2H, s, meso), 7.93 (1H, d), 7.78(1 H, d), 7.71 (1 H, d), 7.64 (1H, d), 7.59 (1H, t), 7.11 (1H, t), 6.87 (2H, d), 6.62 (2H, d), 6.44 (2H, d), 6.23 (2H, d), 4.90 (4H, m), 3.92 (4H, m), 2.76 (3H, s), 2.71 (6H, s), 2.49 (6H, s), 2.02 (6H, t), 1.92 (6H, s), 1.70 (6H, t), 0.65 (9H, s), 0.56 (9H, s), -2.41 (2H, br, NH). 5-(5-Carboxamide-9,9-dimethyl-4-xanthyI)-15-[4-methyI-2,6-bls(4- fart-butyl phenyl)phenyl]-2,8,1 2,18-tetraethyl-3,7,13,1 7-tetramethylporphinato Cobalt (22b): A solution of porphyrin 22a (2 mg) in chloroform (15 ml) and Co(OAc)2 (10 mg) in methanol (2 ml) was refluxed for 2 h under argon atmosphere. After solvents were removed, the porphyrin cobalt complex was obtained in quantitative yield. 1-( 2,6-Dibromo-4-Methylphenyl)-2-nitropropene (24): benzaldehyde 15 (2.78 g, 10 mmol) and NH4OAc (1.1 g, 14mmol) in nitroethane (12 ml) were refluxed for 12 h. The excess nitroethane was removed under vacuum at 70 °C and the residue was chromatographed (silica gel, hexane-dichloromethane) to afford colorless liquid nitropropene 24 (3.20 g, 95.5%). MS, m/z = 334.99 for CmI‘IgBI’zOzN. 1H NMR (300 MHz, CDCI3): 5 =2.07(3H, s), 2.33 (3H, s), 7.40 (2H, s), 7.77(1 H, s). Benzyl 4-methyl-3-(2,6-dibromo-4-methylphenyl)-2-pyrrolecarboxylate (26): To nitropropene 24 (3.35 g, 10 mmol) and benzyl isocyanoacetate 25 (2.0g, 11.5 mmol) in 30 ml dry THF was added dropwise DBU (3.05 g, 20 mmol in 10 ml dry THF) in ice bath and the solution was stirred for 24h at room temperature. Then the solution was poured into HCI (250 ml, 10%) and stirred for 15min. The precipitate was filtered, washed with water and chromatographed (silica gel, hexane-dichloromethane) to give light yellow solid 26 (2.88 g, 62.6%). MS, m/z= 42 462.9 for connerzozN. ‘H NMR (300 MHz, 000.): 6:1.85 (3H, s), 2.26 (3H, s), 5.08 (2H, s), 6.83(1H, d), 7.02 (2H, m), 7.22 (3H, m), 7.31 (2H, s), 9.08 (1H, s). Benzyl 4-methyl-3-[2,6-bis(4-tart-butylphenyI)-4-methylphenyI]-2-pyrrole- carboxylate (27): The a solution of 26 (1 g, 2.16 mmol) in DMF (25 ml) was degassed by passing argon through it for 15min. Then Pd(PPh 3)4 (200 mg), N32C03 (1.06 g in minimum amount of water) and 4-t-butylphenylboronic acid (1 .049, 5.89 mmol) were added to the solution in sequence, and the resulting mixture was refluxed for 48 h under argon atmosphere before it was cooled to room temperature. The mixture was diluted with dichloromethane (30ml), filtered, washed with saturated aqueous NaCl solution (50le3) and dried with N32804. After solvents were removed, the residue was chromatographed (silica gel, hexane-dichloromethane) to gave light yellow solid 27 (0.81 g, 66%). MS, m/z : 569.4 for C40H4302N. 1H NMR (300 MHz, 00013): 6:1.27 (18H, s), 1.57 (3H, s), 2.46 (3H, s), 5.06 (2H, s), 6.47 (1 H, d), 6.88-7.01 (5H, m), 7.11-7.28 (10H, m), 8.60 (1H, s). Dibenzyl 5,5’-di[2,6-bis(4- tart-butylphenyI)-4-methylphenyl]-2,2’-dimethyl- 5,5’-dipyrrylmethanedicarboxylate (28): 27 (569 mg, 1 mmol), methylal (46 mg, 0.6 mmol) and p-toluenesulfonic acid (171 mg, 0.9 mmol) in chloroform (30 ml) were refluxed for 18 h under argon atmosphere. The reaction mixture was then diluted with equal volume of dichloromethane and washed with water twice. The organic layer was separated, dried with NaZSO.t and concentrated. The residue was chromatographed (silica gel, dichloromethane) to give yellow solid dipyrrylmethane 28 (329 mg, 57.2%). MS, m/z = 1150.6 for Ca1H8604N2. 1H NMR (300 MHz, CDCI3): 6:1.19 (42H, s), 2.43 (6H, s), 3.50 (2H, s), 5.01 (4H, s), 6.88- 7.01 (10H, m), 7.11-7.28 (20H, m), 8.82 (2H, s). 5,5’-Di[2,6-bis(4- tart-butylphenyl)-4-methylphenyl]-2,2’-dimethyl-5,5’- dipyrrylmethanedicarboxylic acid (29): Dipyrrylmethane 28 (2.15 g, 1.87 43 mmol) and Pd-C (250 mg, 10%) in methanol (100 ml) was degassed and filled with H2 three times under vacuum and stirred for 48 hr with H2 (1 atm). The mixture was filtered and concentrated to give light yellow solid dipyrrylmethane 29 (1.75 g, 96.55). MS, m/z : 970.8 for C67H7404N2. 1H NMR (300 MHz, 00013): 6:1.13 (42H, s), 2.38 (6H, s), 3.49 (2H, s), 6.94 (8H, m), 7.05 (8H, m), 7.13 (4H, s), 9.34-9.64 (2H, s). 5,5’-Di[2,6-bls(4- ten-butylphenyl)-4-methylphenyl]-2,2’- dipyrrylmethane (30): Dipyrrylmethane 29 (1.75 g, 1.80 mmol) in ethanolamine (40 ml) was refluxed under argon atmosphere for 30min before it was cooled to room temperature. After it was poured into water (200 ml), the precipitate was filtered, washed with water and dried to give white solid dipyrrylmethane 30 (1.45 g, 91.1%). MS, m/z : 882.7 for C55H74N2. 1H NMR (300 MHz, CDCI3): 8:1.25 (36H, 5), 1.29 (6H, s), 2.44 (6H, s), 3.45 (2H, s), 5.93 (2H, d), 6.92 (2H, b), 7.11 (8H, m), 7.15 (8H, m), 7.22 (4H, s). 5,5’-Di[2,6-bis(4- tart-butylphenyl)-4-methylphenyl]-2,2’-dimethyI-5,5’- diformyl dipyrrylmethane (31): Dipyrrylmethane 30 (250 mg, 0.28 mmol) in dry DMF (5 ml) was added dropwise distilled POCla (0.5 ml) in ice bath. The resulting solution was stirred at 0°C for 10 min and at room temperature for 2 h before the excess DMF was removed. The residue was hydrolyzed with saturated sodium carbonate aqueous solution (30ml) at 60 °C for 5min. The yellow precipitate was collected by filtration and washed with water to give the crude formyl dipyrrylmethane 31. It was used for the next step without further purification. MS m/z = 938.6 for C57H7402N2. 2,8-DI[2,6-bls(4- tart-butylphenyI)-4-methylphenyI]-13,17-diethyl-3,7,12,18- tetramehtyI-porphyrin (33): Dipyrrylmethane 31 (260 mg, 0.28 mmol), 33'- diethyl-4,4'-dimethyldipyrrylmethane 32 (63 mg 0.28 mmol) in dichloromethane 44 (150 ml) and 230 mg (1.21 mmol) p-toluenesulfonic acid in methanol (2 ml) was stirred overnight, before a solution of zinc acetate (200 mg0 and sodium acetate (800 mg) in methanol(10 ml) was added and stirred for 12 h. After the solution was washed with water, dried with sodium sulfate and concentrated, the residue was chromatographed (silica gel, dichloromethane:hexane:1 :3 ) to give the zinc (II) porphyrin. It was demetalated by washing with 10% HCI to give porphyrin 33 (25 mg, 8%). UV-Vis (dichloromethane): Max. (rel. int.) = 407.0 (2.405), 503.5 (0.269), 539.0 (0.221 ), 571.5 (0.157), 625.5 (0.114). MS, m/z :1130.5 for 082H90N1. 1H NMR (300 MHz, 00013): 6: -3.97 (2H, s), 0.71 (36H, s), 1.76 (6H, t), 2.71 (6H, s), 3.03 (6H, s), 3.40 (6H, s), 4.00 (2H, q), 6.56 (8H, d), 7.09 (8H, d), 7.60 (4H, s), 9.61 (2H, s), 9.63 (1H, s), 9.89 (1H, s). 13,17-Diethyl-5-(5-formyl-9,9-dimethyI-4-xanthyI)-2,3,7,8,12,18-hexamethyl porphyrin (35): The solution of 3 (162 mg, 0.54 mmol), biladiene 34 (100 mg, 0.17 mmol) and saturated hydrobromic acid acetic acid solution (5 drops) in methanol (25 ml) was refulxed for 24 h under argon atmosphere and then cooled to room temperature. The solution was extracted with dichloromethane (30 ml x 3) and washed with water. After the combined dichloromethane solution was washed with sodium bicarbonate aqueous solution and water, dried with sodium sulfate and concentrated. the dark residue was chromatographed (silica gel, dichloromethane) to give porphyrin 35 (40 mg, 35%). UV-Vis (dichloromethane): AW, (rel. int.) : 402.5 (2.171), 501.5 (0.217), 533.5 (0.125), 570.0 (0.120), 623.0 (0.068). MS, m/z : 686.4 for C45H45N402. ‘H NMR (300 MHz, CDClg): 6: -3.22 (1H, br), -2.99 (1H, br), 1.02 (6H, s), 1.92 (12H, m), 2.56 (6H, s), 3.52 (6H, s), 3.66 (6H, s), 4.10 (4H, q), 7.00 (2H, t), 7.45-7.53 (3H, m), 7.69(1H, d), 7.90 (1H,d), 10.01 (1H, s, meso), 10.17 (2H, s, meso). 1 ,1 9-Dideoxy-2,3,8,12,17,18-hexamethyl-7,13-di[2,6-bis(4- fert-butylphenyl)- 4-mathylphenyl] biladiene-3,0- dihydro bromide (37): Dipyrrylmethane 31 45 (200 mg, 0.21 mmol) and 3,4-dimethylpyrrole 36 (40.5 mg, 0.426 mmol) in methanol (15 ml) containing HBr (1.5 ml, 48% aqueous solution) was first heated for 3 min on steam bath and then stirred for 2 h at room temperature. After it was cooled in refrigerator, the brown precipitate 37 was collected by filtration and washed with 10 ml cold methanol containing a trace amount of hydrobromic acid. Yield: 58%. MS, m/z : 1252.55 for C79H90N4BI'2. 1 2,1 8-Di[4-methyI-2,6-bis(4- tart-butylphenyl)phenyl]-5-(5-formyI-9,9- dimethyI-4-x3nthyI)-2,3,7,8,13,17-hexamethylporphyrin (38): 3 (146 mg, 0.55 mmol) and biladiene 37 (70 mg, 0.055 mmol) and saturated hydrobromic acid acetic acid solution (7 drops) in methanol (30 ml) was refluxed for 24 h: under argon atmosphere and then cooled to room temperature. The solution was extracted with dichloromethane (30 ml x 3). After the combined dichloromethane solution was washed with sodium bicarbonate aqueous solution and water, dried with sodium sulfate, and concentrated, the dark residue was chromatographed (silica gel, dichloromethane) to give phorphyrin 38 (6 mg). UV-Vis (dichloromethane): Max. (rel. int.) = 412.5 (1.339), 507.5 (0.145), 542.0 (0.103), 574.5 (0.095), 628.5 (0.058). MS, m/z for C96H98N4OZ 1338.76. 1H NMR (300 MHz, 00013): 6: 3.42 (1H, br), -3.30 (1H, br), 0.65 (18H, 5), 0.81 (18H, 5), 1.87 (6H, s), 2.40 (6H, s), 2.69 (6H, s), 3.03 (6H, s), 3.23 (6H, s), 6.46 (4H, d), 6.69 (4H, d), 6.96-7.19 (10H, m), 7.39-7.46 (6H, m), 7.57(2H, d), 9.53 (1H, s, meso), 9.67 (2H, s, meso), 10.72 (1H, s, CHO). 12,18-Di[4-methyI-2,6-bis(4- tart-butylphenyl)phenyl]-5-(5-cyano-9,9- dimethyl-4-xanthyI)-2,3,7,8,13,17-hexamethylporphyrin (39): Porphyrin 38 (15 mg), hydroxylamine hydrochloride (10 mg) in 5 ml of 98% formic acid was refluxed overnight under argon atmosphere before cooled to room temperature. After the solution was poured into ice water (80 ml) and neutralized with 10 % sodium hydroxide solution, precipitated porphyrin 39 was collected by filtration (90%). MS, m/z : 1135.76 for 095H97Nso. IR VON 2233.85 cm". 46 12,18-Di[4-methyl-2,6-bis(4- ten-butylphenyl)phenyI]-5-(5- carboxylic acid - 9,9-dimethyl-4-xanthyI)-2,3,7,8,13,17-hexamethylporphyrin (40): Porphyrin 38 (25 mg) in acetone (30 ml) was cooled in ice bath under argon atmosphere. To this solution the Jone’s reagent (3 ml, prepared by dissolving CrO 3 (6.7 g) in H2804 (98%, 6 ml) and then diluted with water (50 ml)) was carefully added. The reaction was kept in ice bath for 1.5 hr and then at room temperature for 1.5 hr under carefully monitoring by TLC. After the reaction was completed, the solution was diluted with water (50 ml) and extracted with dichloromethane (20 ml x 3). The organic solution was dried with sodium sulfate and concentrated. The porphyrin 40 was obtained in 47.4% (12 mg) yield by chromatography (silica gel plate, dichloromethane). MS, m/z : 1354.76 for CgeH93N403. 1 2,1 8-Di[4-methyl-2,6-bis(4- tart-butylphenyl)phenyll-S-(S- Carboxamide -9,9- dimethyl-4-xanthyl)-2,3,7,8,13,17-hexamethylporphyrin (42): Porphyrin 39 (13.5 mg) and sodium hydroxide (50 mg) in ethylene glycol (30 ml) was refluxed for 24 h under argon before cooled to room temperature. After the solution was poured into ice water (200 ml), neutralized with 10% hydrochloric acid and extracted with dichloromethane (30 ml x 3), the combined dichloromethane solution was dried with sodium sulfate and concentrated at reduced pressure to give the crude carboxylic acid porphyrin 40. The crude porphyrin 40 and thionyl chloride (0.25 ml) in dry dichloromethane (10ml) were refluxed for 1 h under argon atmosphere before the solvent and the excess thionyl chloride were removed at reduced pressure. The dark residue was redesolved in dry dichloromethane (10 ml) and ammonia gas was passed through the solution for 1 min. After the solution was diluted with dichloromethane (20 ml), washed with water (15 ml x 2) and dried with sodium sulfate, It was chromatographed (silica gel, 1% methanol/dichloromethane) to give porphyrin 43 (7 mg). UV-Vis (dichloromethane): )wnax. (rel. int.) : 413.0 (1.952), 509.5 (0.207), 544.0 (0.134), 577.0 (0.117), 630.5 (0.071). MS, m/z : 1353.7800 for C96H99N502. ‘H NMR 47 (300 MHz, 00013): 6: -3.33 (2H, br, ring NH), 0.64 (18H, s, t-butyl), 0.83 (18H, s, t-butyl), 1.87 (6H, s), 2.34 (6H, s), 2.68 (6H, s), 2.98 (6H, 5), 3.23 (6H, s), 5.92 (2H, br, NH), 6.48 (4H, d), 6.69 (4H, d), 7.05-7.22 (10H, m), 7.39 (2H, m), 7.43- 7.46 (1H, m), 7.54-7.60 (4H, m), 7.69772 (1 H, m), 7.79-7.83 (1H, m), 8.06-8.09 (1H, m), 9.48 (1 H, s, meso), 9.65 (2H, s, meso). 12,18-Di[4-methyl-2,6-bis(4-tart-butylphenyl)phenyI1-5-(5- Carboxamide -9,9- dimethyl-4-xanthyI)-2,3,7,8,13,17-hexamethylporphyn3to Cobalt (43): Porphyrin 42 (2 mg) in chloroform (15 ml) and Co(OAc)2 (10 mg) in methanol were refluxed for 2 h under argon atmosphere. After the solvents were removed, the porphyrin cobalt complex was obtained in quantitative yield. References: (1) Reed, C. A. In Metal Ions in Biological Systems; Sigel, H. E., Ed.; Marcel Deker, Inc.: New York, 1978; pp277-310. (2) Jones, R. D.; Summerville, D. A.; Basolo, F. Chem. 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