Highly Stereodivergent Approach to Both Enantiomers of 4-Substituted β-Lactams via Diastereofacially Controlled Addition of Enolates oft-Butyl Acetate to a Chiral Imine
an addition reaction of esterenolates to a chiral imine with 1,3-dioxolane, derived from (S,S)-1,4-dimethoxy-2,3-butanediol as a chiral auxiliary, could be fully regulated by the appropriate selection of metal enolates used. Addition of the lithium enolates provided (4S)-β-lactams, while the corresponding (4R)-β-lactams were obtained by the condensation of titanium enolates with the chiral imine.