Extended ketones of the tricyclic terpane series in a Tasmanian tasmanite bitumen

The following novel ketones of the extended tricyclic terpane series (cleistanthane skeleton) were identified in the ketone fraction of a Permian tasmanite bitumen from Tasmania, Australia by HRGC-MS-C and HRGC-MS-MS-C-SRM:C-20; the C-23 13,14-stereoisomers beta beta,alpha beta,beta alpha,alpha alpha; the C-28 and C-33 diastereomers R/S beta alpha and R/S alpha alpha; and higher homologs in lower relative abundance. These tricyclic terpane ketones may be derived from oxidation of the side chain of a tricyclooctaisoprene. The proposed biological precursor for these series is tricyclooctaprenol (C-40), derived from cyclization of octaprenol in the tasmanites algae. (C) 1998 Elsevier Science Ltd. All rights reserved.