3β-Ethyl steranes (5a-c) occur in ancient sediments and petroleum, particularly those of Paleozoic and Proterozoic age. This newly recognised modification to the sterane ring system has no known direct counterpart in the steroid metabolism of extant organisms. When they are present in a sample the pattern of side-chain substitution and some aspects of the isomer distributions of co-occurring 3β-ethyl steranes (5a-c), 3β-methyl steranes (3a-c), 2α-methyl steranes (2a-c), and desmethyl steranes (1a-c) are similar. This suggests that these ring A-alkylated steranes are not synthesised de novo by their source organism(s) but arise via microbial modifications to sedimentary sterenes during the early stages of diagenesis.
|Number of pages||5|
|Journal||Geochimica et Cosmochimica Acta|
|Publication status||Published - 1991|