EXTENDED 3-BETA-ALKYL STERANES AND 3-ALKYL TRIAROMATIC STEROIDS IN CRUDE OILS AND ROCK EXTRACTS

In oils and Precambrian- to Miocene-age source rocks from varying depositional environments, we have conclusively identified several novel 3-alkyl sterane and triaromatic steroid series, including (1) 3 beta-n-pentyl steranes, (2) 3 beta-isopentyl steranes, (3) 3 beta-n-hexyl steranes, (4) 3 beta-n-heptyl steranes, (5) 3,4-dimethyl steranes, (6) 3 beta-butyl,4-methyl steranes, (7) triaromatic 3-n-pentyl steroids, and (8) triaromatic S-isopentyl steroids. We have also tentatively identified additional homologs with 3-alkyl substituents as large as C-11. The relative abundances of these compounds vary substantially between samples, as indicated by (1) the ratio of 3 beta-n-pentyl steranes to 3 beta-isopentyl steranes and (2) the ratio of 3-n-pentyl triaromatic steroids to 3-isopentyl triaromatic steroids. These data suggest possible utility for these parameters as tools for oil-source rock correlations and reconstruction of depositional environments. Although no 3-alkyl steroid natural products are currently known, several lines of evidence suggest that 3 beta-alkyl steroids result from bacterial side-chain additions to diagenetic Delta(2)-sterenes.