The isomeric biliverdins from ring-cleavage of deuteroporphyrin-IX

Summary Treatment of zinc(II) deuteroporphyrin-IX dimethyl ester with thallium(III) trifluoroacetate, followed by acid treatment, affords the four isomeric oxophlorins (oxyporphyrins) in a reaction which is considerably more easy to control than the traditional method involving “coupled oxidation” of the corresponding hemin. The oxophlorins, obtained in very high yield, are chromatographically separable on a preparative scale. Using nuclear Overhauser enhancement and NMR spin-decoupling experiments, the isomeric deuterobiliverdins and meso-acetoxyporphyrins derived from the isomerically pure oxophlorins are assigned definitive structures. This work suggests that the original assignments of the β- and δ- deuterobiliverdins, made on the basis of coupled oxidation of deuterohemin-reconstituted hemoglobin, should be reversed. Implications for heme orientation in deuterohemin-reconstituted hemoglobin are discussed.