The Synthesis of Porphyrins Derived From Chlorobium Chlorophylls

Abstract

The proofs of the structures proposed for the Chlorobi~rnl pheophorbides 650, fractions 1-3, and for the Chlorobizrn~ pheophorbides 660, fractions 5 and 6, are completed and the degradational evidence, where parallel, confinned through the synthesis of derived porphyrins.The photosynthetic bacteria Clllorobizim thioszilfatoplzilum, strain L and strain VN, contain Chlorobium chlorophyll 650 and Chlorobiz~nz cl~loropl~yll 660 respectivelj., the numbers indicating the wavelength of their absorption maxima in the red. These are magnesium complexes of farnesyl (not phytyl) esters of the Chlorobium pheophorbides 650 and 660. Like ordinary chlorophyll, both these cl~lorophylls are mixtures, for their pheophorbides can be resolved into several con~ponents, which are termed fractions: Cl~lorobium pheophorbide 650, fractions 1-6, and Chlorobium pheophorbide 660, fractions 1-6.These fractions (pheophorbides) are more closely related to the pyrropheophorbide a than to the pheophorbide a from cl~lorophyll a , for they lack the 10-carbomethoxy group of the latter. All were shown to be homologues of 2-(a-hydroxyethy1)-2-desvinyl-pyrropheophorbide a (I, R1 = E t , R2 = Me, R3 = H) (Reaction Scheme 1) and were forinulated (2,3) as shown in Table I , wherein the structures of the related porphyrins as well as soine chlorophyll a derivatives are also indicated. I t will be noted that some trivial names such a s pyrroporphyrin (strictly pyrroporphyrin l5), phylloporphyrin, and desoxo-phylloerythrin are used in two senses. Without qualification, they refer to the prototypes derived from chloropl~yll a ; otherwise, they refer to the homologues of these, derived fro111 the Cizlorobium chlorophylls.The analytical and degradational evidence (2, 3) did not coillpletely prove these structures for, in the absence of special features, it could only reveal the pairs of substituents on positions 1-8 but not their order. In both the 650 and 660 series other structures in which the substituents on any of the pyrrole rings 1, 2, or 4 n-ere reversed in order (e.g. 7-methj~l-8-propionic acid) were equally compatible with it. The indicated structures 1 1 ere preferred, because they \\-ere Inore obviously related to pheophorbide a .In the G50 series, there was no direct evidence concerning the nature of R2 in fractions 3 , 5 , and 6, for citraconimide had not been detected among their oxidation products.In the 660 series, improved analytical methods revealed the natures of R2 in all fractions.However, in the absence of adequate models, the nuclear magnetic resonance evidence xvhich placed the R3 groups on the 6-positions xvas not conclusive (3, 4)

Synthèse de méso-α,γ bis(diamino-2,6 phényl) porphyrines

“…Le pyrrole 26 est transform6 en pyrrole l a selon la mCthode de McDonald et al (8): l'oxydation du pyrrole 26 par 3 Cquivalents de chlorure de sulfuryle, suivie d'un traitement a 1'Cthanol conduit au diester 2c dont l'hydrogknolyse fournit l'acide 2d. La dkcarboxylation de l'acide 2d selon la methode de Battersby et al (9) conduit au pyrrole l a qui est transestkrifik en pyrrole 16.…”

“…: C 68,33, H 6,15, N 7,77; tr. : C 6 8 3 , H 5,93, N 7,98. De la mCme manikre est obtenu le dipyrrylmethane 6i A partir du 1360 cm-'; rmn 'H (CDCI,): 1,7 (s, 6H), 2,2 (s, 6H), 5,2 (s,4H),6,2 (s,IH),8 (m,13H),8,8 (s large,2H). Anal.…”

Crude Petroleum

“…He also found evidence for the presence of a rhodo series. These petroporphyrins (see Chapter 19) may perhaps be related to the plant chlorophylls like those produced by photosynthetic Chlorobium bacteria [163]. They are encountered principally as their vanadyl and nickel complexes [16,164], are quite stable, and are found in petroleum distillates boiling above 500° C. Carboxylated porphyrins have been reported in petroleum [165,166] but the metal porphyrins of the deoxophyllo-and etio-series appear to be the principal petroporphyrins, whose concentration in petroleum may range from 1 to 1,000 ppm.…”

EFFECT OF LEWIS ACID CATALYSTS ON THE POSITIONAL SELECTIVITY OF THE ELECTROPHILIC AROMATIC SUBSTITUTION ON Α-Substituted THIOPHENES: A CONCEPTUAL DFT INVESTIGATION

“…4 The EASs on five-membered heterocycles ranks as an extensively researched topic in organic chemistry. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] For instance, Linda and Marino 8 compared the reactivity of furan and thiophene in the catalyzed acetylation. Clementi and Marino 9 have determined the relative rates for the reaction of thiophene, selenophene, furan, and pyrrole.…”