The identification and geochemical significance of a second series of alkylthiophenes comprising a linearly extended phytane skeleton in sediments and oils

A series of 5-n-alkyl-2-(3,7,11-trimethyldodecyl)-3-methylthiophenes (C₂₁–C₂₆), which possess a linearly extended phytane skeleton, have been identified in a number of bitumens and oils. The carbon skeletons of the C₂₄–C₂₆ members of this series are unusual since they comprise an isoprenoid and a linear part. This series of compounds, and a related series of 2-n-alkyl-5-(3,7,11,15-tetramethylhexadecyl) thiophenes, is probably formed by abiogenic sulphur incorporation into functionalised precursor lipids with similar carbon skeletons, possibly biosynthesised by halophilic archaebacteria