Synthesis of type III isomers of diacetyldeutero-, hemato-, and protoporphyrins with the use of Knorr's pyrrole

Derivation of the Knorr's pyrrole with 2-ethyl and 4-benzyl mixed-ester groups into 3,3′-diacetyl-5,5′-diiodo-4,4′-dimethyl-2,2′-dipyrromethane was developed. Coupling of the dipyrromethane with 5,5′-diformyl-3,3′-bis(2-methoxycarbonylethyl)-4,4′-dimethyl-2,2′-dipyrro-methane afforded in a reasonable yield diacetyldeuteroporphyin III with C2v symmetry. The porphyrin was further converted to protoporphyrin III through hematoporphyrin III. Utilization of readily available Knorr's pyrrole as the starting material much facilitates the access to symmetric iron porphyrins which are free from the orientational disorder in hemoprotein pocket.