Hydroxylation of protoporphyrin dimethyl ester (I) by means of osmium tetroxide afforded the bis(glycol) derivative (II). This was condensed with carborane carbonyl chloride (III) in the presence of dimethylaminopyridine to provide tetraester (IV). Acid hydrolysis of the methyl ester groups, followed by complexation with manganese diacetate and passage through an ion exchange resin furnished the title compound.