Identification of a sulfide derivative with a bicyclic hydrocarbon skeleton related to squalene. Part II: synthesis of a S-spiro-like dithiolane triterpenoid

摘要

A sulfide with a bicyclic squalene hydrocarbon skeleton present in sediments from Various depositional settings and of different geological age has been identified by synthesis of a reference compound. In contrast to previous expectations [cf. Schouten, S., Sinninghe Damste, J.S., de Leeuw, J.W., 1995. A novel triterpenoid carbon skeleton in immature sulphur-rich sediments. Geochimica et Cosmochimica Acta 59, 953-958; Gug, S., Schaeffer, P., Adam, P., Klein, S., Motsch, E., Albrecht, P., 2009. Identification Of a Sulfide derivative with a bicyclic hydrocarbon skeleton related to squalene. Part 1: Synthesis of a dithiane triterpenoid. Organic Geochemistry 40, 876-884.], this sulfide bears two "S-spiro type" thiolane moities, but not the two thiochromane moieties Originally envisaged. The synthesis resulted in the formation of a complex isomeric mixture of compounds, all co-eluting in gas chromatography (GC) in the form of one broad peak, as is the case with the geochemical compound. The spiro-type sulfide was formed by intramolecular sulfurization of a polyunsaturated bicyclic squalene derivative of unknown biological Origin. The presence of this sulfide in a number of Triassic to Miocene marine sediments from various and contrasting depositional settings (upwelling environments, shallow continental platforms, lagoonal subbasins, hypersaline environments), all characterized by Strongly anoxic conditions, but with OF without photic zone anoxia, indicates that the microorganisms biosynthesizing the precursor bicyclic squalene occupy diverse ecological niches.