The wide diversity of hopanoid sulfides evidenced by the structural identification of several novel hopanoid series

We describe the structural elucidation of four novel series of hopanoid sulfides bearing a thiane or a thiolane ring fused to the pentacyclic hopanoid skeleton and the partial identification of an additional spiro-type hopanoid sulfide series which occurs in various immature sulfur-rich sediments and crude oils. These novel diagenetic hopanoid derivatives have been identified either by isolation of one member of the series, followed either by nuclear magnetic resonance (NMR) structural characterization, by synthesis of a reference compound or by deuterium labelling experiments. Location of the C-S bonds between the C-30 or C-31 positions from the side chain and the C-16, C-17, C-20 or C-21 positions in rings D or E of the polycyclic hopanoid skeleton likely indicates that intramolecular sulfurization occurred on precursor molecules functionalized at C-17 and C-21, such as hop-17(21)-ene derivatives, but also, for some of them, at C-16 or C-20. The predominance of one series over the others is variable within the different samples. Their occurrence in a wide variety of sediments and crude oils of different maturity and ranging in age from Triassic to Upper Miocene suggests that the precursor molecules which underwent sulfurization are relatively widespread and that the sulfurization processes involved in their formation are operative during early diagenesis.