Pyrroles and related compounds. Part XXV. Pemptoporphyrin, isopemptoporphyrin, and chlorocruoroporphyrin (Spirographis porphyrin)

Abstract

Pemptoporphyrin (4-vinyldeuteroporphyrin-IX dimethyl ester) and its 2-vinyl isomer have been synthesised by application of the b-oxobilane and a-oxobilane routes, respectively, thus providing a definitive proof of structure for the natural material. The vinyl groups in each case were introduced through transformation of acetoxyethyl side-chains. Formylation of one of the intermediates (4-chloroethyldeuteroporphyrin), followed by base-catalysed elimination of hydrogen chloride, afforded the dimethyl ester of chlorocruoroporphyrin (2-formyl-4-vinyldeuteroporphyrin-IX).