Dynamic Kinetic Resolution Utilizing 2-Oxoimidazolidine-4-carboxylate as a Chiral Auxiliary: Stereoselective Alkylation of α-Bromo Amides with Malonic Ester Enolates

Stereoselective carbon−carbon bond formation by dynamic kinetic resolution using tert -butyl (4 S )-1-methyl-2-oxoimidazolidine-4-carboxylate ( 1 ) as a chiral auxiliary was developed. Reaction of a diastereomeric mixture of tert -butyl (4 S )-3-[(2 RS )-2-bromoacyl]-1-methyl-2-oxoimidazolidine-4-carboxylates ( 2 ) with a malonic ester enolate in HMPA predominantly afforded tert -butyl (4 S )-3-[(2 R )-2-alkyl-3,3-bis(alkoxycarbonyl)propionyl]-1-methyl-2-oxoimidazolidine-4-carboxylate [( S, R )- 8 ] in good yields. The stereoselectivity of this reaction was in accordance with our working hypothesis based on the conformational analysis of 2 and elucidated the unique characteristics of 1 as a novel chiral auxiliary for dynamic kinetic resolution. The alkylated products ( S, R )- 8e, j, k were easily converted to chiral α-alkyl succinic acid derivatives and chiral β-amino acid derivatives, both of which have been known as key building blocks for the syntheses of a variety of biologically active compounds.