4 POLYMETHYLSQUALENE EPOXIDES AND ONE ACYCLIC TETRATERPENE EPOXIDE FROM BOTRYOCOCCUS-BRAUNII

New terpene epoxides have been isolated from two strains of the green microalga Botryococcus braunii. Polymethylsqualene epoxides C-32, C-33 and C-34 are 10,11-epoxysqualene derivatives with non-isoprenoid meth yls at C-3, C-7, C-18 and (or) C-22; they were isolated from a strain producing large amounts of triterpene hydrocarbons (B. braunii, B race ). Epoxylycopaene is an acyclic tetraterpene with a trans epoxide occu rring at C-14, C-15 and a trans unsaturation at C-18; it was obtained from a strain characterized by the production of trans,trans-lycopadie ne, a tetraterpene hydrocarbon (B. braunii, L race). The structures we re determined by NMR and mass spectrometry. Chemical degradation and a pplication of Mosher ester methodology allowed us to establish the abs olute stereochemistry of epoxylycopaene. In addition, 14,15-dihydroxy lycopa-18-ene has been isolated from the L race. Copyright (C) 1997 El sevier Science Ltd.