SYNTHESIS OF A BICYCLIC CATION RELATED TO STEROL BIOSYNTHESIS AND ITSCHEMICAL DESTINY, PART I

Synthesis of bicyclic tert-alcohol 1 has been accomplished by means of Hg(OTf)(2)-induced cyclization of tert-butyl bishomofarnesafe as the key step. Bicyclic cation 2, related to the sterol biosynthesis, is ge nerated by the reaction of 1 with BF3. The chemical destiny of the cat ion 2 was traced and it confirmed the structure of three kinds of cycl ization products to be 3, 4, and 5. These tricyclic compounds are form ed via trans-anti-trans 6/6/5 fused cation 6. The tricyclic product 3 is the stereoisomer with Corey's enzymatic cyclization product of a 2, 3-oxidosqualene type epoxide. Selective formation of the trans-anti-tr ans 6/6/5 fused cation 6 as the intermediate that corresponds to the b iosynthetic intermediate of a dammarane-type triterpenoid is noteworth y.