Three series of non-isoprenoidal dialkyl glycerol diethers in cold-seep carbonate crusts

摘要

Three novel series of non-isoprenoidal dialkyl glycerol diethers with an inferred sn-l,2 stereochemistry were tentatively identified in carbonate crusts precipitated from methane-rich bottom-waters and pore-waters associated with Medi- terranean mud volcanoes. In the first series of diethers, an I I, 12-methylenehexadecyl moiety is ether-bound at the ,l'n-2 position of the glycerol group, and in diethers from the second series, an anteiso pentadecyl group is ether-bound at the sn-2 position. In the third and minor series a pentadecyl moiety is ether-bound at the sn-2 position. In all series, ether- bound C14-C17 alkyl units (either n-alkyl, branched alkyl, alkylcyclohexyl or methylenealkyl) occur at the sn-1 position. The two major series are also distinguished by their ~13C values, which differ by 15-300/00 at the sites studied. Only the minor series has been previously reported in sediments. Members of the second and third series are similar to diethers containing C16-C18 iso, anteiso, and n-alkyl units present in the thermophilic bacteria Thermodesu(fobacterium com- mune. Ammonifex degensii and Aquife.: p}.rophilus. The first series is unique, in that diethers possessing alkyl chains that contain a cyclopropane ring have never been reported.