Novel Asymmetric Approach to Proline-Derived Spiro-β-lactams

We describe a novel asymmetric approach using Staudinger chemistry to proline-derived spiro-beta-lactams. A chiral group at C-4 of the acid chloride of proline directs the stereoselectivity of Staudinger chemistry and later is sacrificed to obtain optically active 5.4-spiro-beta-lactams. The scope, limitations, and mechanistic rationale for the observed results of Staudinger Chemistry of the acid chloride of 4-alkyl(aryl)sulfonyloxy-l-proline with imines are also discussed.