Pyrroles and related compounds. Part XV. Differential protection of pyrrole rings during porphyrin synthesis. Syntheses of mesoporphyrin-XI

Abstract

The preparation is described of pyrromethanes bearing a 5-benzyloxycarbonyl group and, in the 5′-position, either a t-butyloxycarbonyl or a pentachlorophenyloxycarbonyl group. These compounds are useful intermediates in porphyrin synthesis through b- and a-oxobilanes respectively, because the 5′-position can be selectively uncovered by the appropriate treatment with either trifluoroacetic acid or alkali. Mesoporphyrin-XI dimethyl ester has been synthesised by both routes.