Novel C26 highly branched isoprenoid thiophenes and alkane from the Menilite Formation, Outer Carpathians, SE Poland

A novel C26 HBI alkane [2,6,10,13,14-pentamethyl-7-(3′-methylpentyl)pentadecane] and C26 highly branched isoprenoid (HBI) thiophenes, possessing the same carbon skeleton, have been tentatively identified in sediments of the Oligocene Menilite Formation of the Outer Carpathians, SE Poland. The structural identity of these compounds has been assigned by mass spectral and relative retention time data, and by desulfurization followed by hydrogenation of the C26 HBI thiophenes. The C26 HBI compounds show structural similarities to known C25 HBIs but possess an additional methyl group at C-13. The identical thiophene isomer distribution and similar stable carbon isotope compositions of the C25 and C26 HBI thiophenes point towards a biological HBI precursor polyene with double bonds in the same position, probably originating from the same diatom species.