Structures and transformations of the bacteriochlorophylls e and their bacteriopheophorbides

Abstract

Methyl bacteriopheophorbides e (Bpheo e) isolated from Chlorobium phaeovibrioides (NCIB no. 4832 and strain B1-28) and Br. zenitani were investigated by reversed-phase high-performance liquid chromatography. Structures of individual Bpheo e homologues were examined by NMR spectroscopy and were found to be consistent with previous literature proposals, but with one exception. The stereochemistry at the chiral 2-(1-hydroxyethyl) position was found to change from primarily (R) for the 4-ethyl-4-ethyl homologue to primarily (S) for the 4-isobutyl-5-ethyl compound. This observation is consistent with what has been reported for the Bpheo c and Bphe d. Identification of the 2-(1-hydroxyethyl) group in the Bpheo e was facilitated by their transformation into the Bpheo c without loss of diastereomeric purity.