STRUCTURE ELUCIDATION AND BIOSYNTHESIS OF 31-METHYLHOPANOIDS FROM ACETOBACTER-EUROPAEUS - STUDIES ON A NEW SERIES OF BACTERIAL TRITERPENOIDS

Apart from a mixture of bacteriohopanetetrols already found in other A cerobacter species, four new 3 beta-methylhopanoids have been isolated from Acetobacter europaeus. All of them present an ether linkage betw een a bacteriohopanetetrol or a bacteriohopanepentol and a carbapseudo pentose moiety often found in bacterial hopanoids. Three of these ethe rs were shown by comparison with synthetic reference hopanoids to pose ss a supplementary methyl group at C31. This novel series of methylhop anoids may be the precursor of yet unidentified molecular fossils foun d in sediments. [methyl-H-2(3)]Methionine was efficiently incorporated into the 31-methylhopanoids with retention of all three deuterium ato ms in the transferred methyl group. This labelling pattern might be co nsistent with a rather rarely found methylation reaction of an enol.