Total synthesis of taxane terpenes: cyclase phase.

A full account of synthetic efforts toward a lowly oxidized taxane framework is presented. A non-natural taxane, dubbed "taxadienone", was synthesized as our first entry into the taxane family of diterpenes. The final synthetic sequence illustrates a seven-step, gram-scale and enantioselective route to this tricyclic compound in 18% overall yield. This product was then modified further to give (+)-taxadiene, the lowest oxidized member of the taxane family of natural products.