Studies on taxol biosynthesis. Preparation of taxa-4(20),11(12)-dien-5 alpha-acetoxy-10 beta-ol by deoxygenation of a taxadiene tetraacetate obtained from Japanese yew.

Taxa-4(20),11(12)-dien-5 alpha-acetoxy-10 beta-ol 6 has been identified as an early stage intermediate involved in the biosynthesis of taxol (Paclitaxel). This compound has been efficiently prepared by Barton deoxygenation of the C-2- and C-14-hydroxyl groups on a derivative semisynthetically prepared from taxa-4(20),11(12)-dien-2 alpha,5 alpha,10 beta-triacetoxy-14 beta-(2-methyl)butyrate (7), a major taxoid metabolite isolated from Japanese yew heart wood. The synthetic methodology is amenable for the preparation of isotopically labeled congeners that will be useful to probe further intermediate steps in the biosynthesis of taxol.