Studies on the structure of a pigment related to chlorophyll a produced by Rhodopseudomonas spheroides

Abstract

A pigment (compound-2) from cultures of R. spheroides grown in the presence of 8-hydroxyquinoline resembled Chlorobium phaeophorbid (650) and 2-devinyl-2-hydroxyethylphaeo-phorbid-a in spectroscopic properties. Unlike Chlorobium phaeophorbid (650), it gave a positive phase test, indicating the presence of the isocyclic ring with carboxymethyl substituent at C-10. Chromatographic tests confirmed by an oxidative reaction indicated that compound-2 possessed a hydroxylated side chain. Dehydration of compound-2 yielded a product which was virtually identical with phaeophorbid-[alpha], both spectroscopically and chromatographically. This suggests that compound-2 is 2-devinyl-2-hydroxyethylphaeophorbid-[alpha]. The presence of methanol as an esterifying group was confirmed by quantitative analysis. Compound-2 may be closely related to an intermediate in the synthesis of bacteriochlorophyll.