A NOVEL SERIES OF BENZOHOPANES WIDESPREAD IN SEDIMENTS

A novel series (C31-C35) of benzohopanes cyclized at the C(16) positio n has been characterized by gas chromatography-mass spectrometry and N MR structural elucidation of the usually predominant C31 member, the 4 '-methylbenzo[16,17,21]-22,29,30-trinorhop-16-ene isolated from the Me ssel shale (Germany). These biological markers of bacterial origin see m to be widely distributed in sediments and to show low specificity wi th regard to the depositional environment, although they are well repr esented in evaporites. Up to now, they have been detected only in ther mally immature samples, which could reflect either a relative fragilit y or other possibilities of transformation as compared to the regular benzohopanes cyclised at C(20).