Alkyl carboxamides derived from the N-acylation of the oxazolidinone form enolates which undergo highly enantioselective aldol condensation with aldehydes. The products readily undergo hydrolysis, e.g. with base, to give chiral ? -hydroxyacids, with consequent easy recovery and recycle of the chiral auxiliary: J. Am. Chem. Soc., 103, 2127 (1981); Tetrahedron, 27, 897 (1986); Tetrahedron Lett., 31, 4699 (1990); J. Org. Chem., 56, 2489 (1991). The enolates of the N-acyloxazolidinones can also undergo a variety of other enantioselective reactions including alkylation: J. Am. Chem. Soc., 104, 1737 (1982); acylation: J. Am. Chem. Soc., 106, 1154 (1984). Bromination (NBS), followed by azide displacement, gives a route to chiral amino acids: Tetrahedron Lett ., 28, 1123 (1987). Direct electrophilic azidation with triisopropylbenzenesulfonyl azide has also been used to effect this transformation: J. Am. Chem. Soc., 112, 4011 (1990).
