A novel triterpenoid carbon skeleton in immature sulphur-rich sediments

A novel S compound, 1,4-bis(2',5',5',8a'-tetramethylhexahydrothiochroman)-butane has been detected in several immature S-rich sediments, of which the desulphurized counterpart was unambiguously identified by synthesis of an authentic standard and coinjection experiments. This C skeleton of the S compound, 1,10-bis(2',2',6'-trimethylcyclohexyl)-3,8-dimethyldodecane(I), has not been reported yet in any sediment or organism. We suggest that it may be biosynthesized through an enzymatic cyclization reaction of squalene (II), which shows similarities with the biosynthesis of β,β-carotene (III) from lycopene (IV).