The carbohydrate-sesquiterpene interface. A zirconocene-mediated synthesis of (+)-epiafricanol from D-glucose

A total synthesis of (+)-epiafricanol (6) has been readily achieved from D-glucose. The tricyclic alcohol target was arrived at by first forming m, ethyl 6-O-benzyl-2-deoxy-2-C-methyl-alpha-D-altropyranoside (12) and converting this intermediate into methyl 2-C-methyl-2,3,4-trideoxy-alpha-D-threo-hexopyranoside (14). There followed a series of steps resulting in extension of the side chain to give the isopropenyl pyranoside 9. This advanced intermediate was subjected to zirconocene-promoted ring contraction, which gave rise to 8 and set the stage for conversion to 7. This tertiary carbinol was transformed into 6 by sequential ring-closing metathesis and stereodirected Simmons-Smith cyclopropanation.