132(S)–OH methyl bacteriopheophorbide a allomer in sedimentary organic matter

We report the structure determination (RP-18 HPLC, UV–vis, MS, 1H NMR) of the purified 132(S)–OH methyl bacteriopheophorbide a allomer isolated from a coastal salt pond sediment (Salt Pond, MA, USA). This compound, which occurs with its pheophytin counterpart, is a new bacteriochlorophyll a molecular fossil and may be an intermediate in the formation of some ETIO porphyrins previously isolated from ancient sediments.