Synthetic and biosynthetic studies of porphyrins. Part 10.¹ Syntheses of porphyrins with acetic, propionic, and butyric acid side-chains for biosynthetic studies

In connection with studies of substrate specificity of uroporphyrinogen decarboxylase and coproporphyrinogen oxidase, enzymes in the heme and chlorophyll biosynthetic pathways, and heme oxygenase, an enzyme involved in the catabolism of hemes, we have synthesized a number of new porphyrins substituted with acetic, propionic, and butyric side-chains, using the a, c-biladiene route; one porphyrin was also prepared by the MacDonald pyrromethane approach. In one of the a, c-biladiene cyclizations, meso-chlorinated porphyrins were formed as minor by-products, but this side-reaction was suppressed by carefully drying the copper(II) chloride used in this stage, or by use of copper(II) acetate as an alternative oxidant.