STEREOSPECIFIC AMINATION BY DYNAMIC KINETIC RESOLUTION UTILIZING 2-OXOIMIDAZOLIDINE-4-CARBOXYLATE AS A NOVEL CHIRAL AUXILIARY

A novel type of stereospecific amination by dynamic kinetic resolution using (4S)-2-oxoimidazolidine-4-carboxylate (1) as a chiral auxiliary was developed. A reaction of a diastereomeric mixture of (4S)-3-[(2RS)-2-bromoacyl]-2-oxoimidazolidine-4-carboxylates 4 with an amine in the presence of a base in HMPA predominantly afforded (4S)-3-[(2R)-2-(alkylamino)acyl]-2-oxoimidazolidine-4-carboxylates (S,R)-7 in good yields. The reaction proceeded by stereospecific S(N)2 type amination incorporated with rapid interconversion between the substrates (S,S)-4 and (S,R)-4. Mechanistic study suggested that the unique stereoselectivity was induced through the interaction between an amine and the ester group of (S,S)-4 in the transition state. The chiral auxiliary was easily removed with alkoxide anion to afford the alpha-amino acid synthon in good yields.