NOVEL EXTENDED SIDE-CHAIN-UNSATURATED HOPENES RELEASED FROM THE KEROGEN MACROMOLECULES UNDER ARTIFICIAL CONDITIONS

A novel family of hopanoids present in pyrolysates of solvent-extracte d peal from Caohai Basin, Southwest China, has been tentatively identi fied on the basis of GC-MS data as C-32-C-35 extended side-chain-unsat urated hopenes. These unsaturated pentacyclic triterpenoid compounds a re produced by laboratory thermal decomposition of kerogen. The result s of our pyrolysis experiments suggest that these structures result fr om thermal release of bound C-35 bacteriohopanepolyols which are bonde d to the kerogen macromolecule via polyether or polyester linkages. Th e finding of these new hopenes indicates that pyrolysis can provide in formation about the types of linkings and sites of bonding of hopane u nits to the macromolecular network. Meanwhile, this study also provide s valuable information on the way that these hopane skeletons are rele ased from a kerogen structure under thermal stress. These novel extend ed side-chain-unsaturated hopenes may act as intermediates in the tran sformation of bound C-35 hopanoid precursors to free C-27-C-35 hopanes under artificial conditions. Copyright (C) 1996 Elsevier Science Ltd