Studies on the Lithiation of Hydroxypyrrolidines: Synthesis of Polyhydroxylated Pyrrolidines via Chiral Enecarbamates

The chiral endocyclic enecarbamate 14 has been obtained by deprotonation-elimination from the N-Boc pyrrolidine 5 (or its racemic counterpart from 15). Efficiently stereocontrolled epoxidation-methanolysis of 14 afforded ?-alkoxy carbamates, which undergo completely stereoselective nucleophilic substitutions to give trisubstituted dihydroxypyrrolidines