Diastereoselective synthesis of alpha-tocopherol: a new concept for the formation of chromanols.

A diastereoselective synthesis of alpha-tocopherol 1 (93% de) was achieved via two key steps, (i) a highly diastereoselective Shi epoxidation of a trisubstituted alkene and (ii) an acid supported, "anti-Baldwin" epoxide ring opening under inversion of configuration leading to the 6-membered chromanol ring.