Highly diastereoselective aldol additions to five-ring N,O-acetals

Highly diastereoselective aldol additions of pure (2R,4S)-2-tert-butyloxazolidinone-3,4-dicarboxylic acid 3-tert-butyl ester 4-methyl ester 1 are reported. While achiral carbonyl compounds lead to mixtures of diastereomers, the double stereodifferentiation of chiral aldehydes gave a single product isomer. The relative and absolute configurations of the aldol products were assigned by NOESY.