Topical Problems in the Biosynthesis of Red Blood Pigment

Abstract

Uroporphyrinogen 111 plays a key role in the biosynthesis of heme, the red pigment of blood. In uiuo studies with specifically I4C-and 3H-labeled precursors have revealed that the formation of uroporphyrinogen I11 in the organism follows several primary and subsidiary pathways. Model experiments on the pattern of biosynthesis have led to simple and effective methods of synthesizing uroporphyrin analogs and have shown that their production is strongly favored thermodynamically. The biologically important porphyrins thus available permit a mechanistic explanation of the light-induced dermatoses in porphyria diseases and suggest promising medical applications in diagnosis and therapy.

Synthesis and Structural Features

“…Esters of porphyrin octa-acetic acid were prepared according to Scheme 43, porphyrin octa-acetic acid being prepared following the procedure of Franck [160]. Consequently, a Knorr condensation be-tween acetyl acetone and 3-aminodimethylpentandioate (generated in situ) gives the pyrrole 36.…”

Syntheses of Some Unusual Polypyrrole Macrocycles

“…The above assiqnements are corroborated by the 'H-nmr spectrum of dodecamethylhexaphyrin (7b) in which only two singulets at 6 12.5 and -7.3 ppm are present, corresponding to the exo and endo methine protons respectively. The peripheral methyl groups give rise to two signals at 6 4.55 and 4.60 ppm.…”

“…6 12.33 and 12.19 ppm are assigned to the two pairs of homotopic methine protons of isomer 7a which belongs to the symmetry group CZh. Moreover, the protons at the methine bridges which are directed inside the macrocycle aive rise to two signals at 6 -7.40 and -7.54 pprn corresponding to each one of the isomers 6 and 7a. A s both signals have approximately the same intensity, the two isomers must be present in about the same concentration despiteofthe fact that the relative statistical probabilities for the formation of 7a and 6 are 2 to 1. Most likely, isomer 6 is thermodynamically favoured owing to the smaller sterical repulsion between the methyl groups attached to the pyrrole rings adjacent to the E-configurated methine bridges.…”

“…The blue-green pentaphyrin 5 displays on exceptionally Stimulated by the success on synthesizinq pentaphvrin, we attempted the hexapyrrole macrocycle shows three signals associated with the protons at the Z-configurated methine bridges whose relative intensities are 2:l:l. The singlet at 6 12.42 ppm corresponds to the four homotopic methine protons of isomer 6 which belongs to the symmetry group DZh. 6 12.33 and 12.19 ppm are assigned to the two pairs of homotopic methine protons of isomer 7a which belongs to the symmetry group CZh.…”

ChemInform Abstract: SYNTHESES OF SOME UNUSUAL POLYPYRROLE MACROCYCLES

“…The blue-green pentaphyrin 5 displays on exceptionally Stimulated by the success on synthesizinq pentaphvrin, we attempted the hexapyrrole macrocycle shows three signals associated with the protons at the Z-configurated methine bridges whose relative intensities are 2:l:l. The singlet at 6 12.42 ppm corresponds to the four homotopic methine protons of isomer 6 which belongs to the symmetry group DZh. 6 12.33 and 12.19 ppm are assigned to the two pairs of homotopic methine protons of isomer 7a which belongs to the symmetry group CZh.…”