Asymmetric Synthesis of Substituted Prolines from δ-Amino β-Ketoesters. Methyl (2S,5R)-(+)-5-Phenylpyrrolidine-2-carboxylate

[reaction: see text]. Metal carbenoid chemistry is used to convert delta-amino beta-ketoesters into 5-substituted 3-oxo prolines, which expands the utility of this class of polyfunctionalized chiral building blocks.