Dynamic kinetic resolution of racemic α-halo acids via a chiral imidazolidinone auxiliary
作者:Jeff A. O'Meara、Manfred Jung、Tony Durst
DOI:10.1016/0040-4039(95)00339-e
日期:1995.4
A dynamickineticresolution is utilized to realize highly diastereoselective nucleophilic displacement of bromine in tert-butyl (4S)-1-methyl-3-(2-bromoacyl)-2-oxoimidazolidine-4-carboxylates (6a-f) by benzylamine enroute to tert-butyl (4S)-1-methyl-3-(2-benzyaminoacyl)-2-oxoimidazolidine-4-carboxylates (7a-e).
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.