Intramolecular Ester Enolate–Imine Cyclization Reactions for the Asymmetric Synthesis of Polycyclic β-Lactams and Cyclic β-Amino Acid Derivatives

Enolates of chiral N-(α-methyl-p-methoxybenzyl)-ω-imino-esters undergo intramolecular cyclization reactions to afford (syn)-aza-anions of β-amino esters in high dr that cyclize to afford N-(α-methyl-p-methoxybenzyl)-β-lactams that can be readily deprotected to afford their corresponding cyclic NH-β-lactams, β-amino esters, or β-amino acids.