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

We describe a novel asymmetric approach using
Staudinger chemistry to proline-derived spiro-β-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-β-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.