Asymmetric Lewis Acid-Catalyzed Addition of a Ketene Dithioacetal to a Chiral Bicyclic Lactam. Formation of Cyclobutanopyrrolidinones. A New Class of GABA Derivatives

Article abstract of DOI:10.1021/jo00119a012

Additions to unsaturated chiral lactams 8 using methylenedithiolane, gave very high endo-selectivity of the cyclobutane adducts (2 + 2 addition) 13, 16.Removal of the phenylglicinol auxiliary by reductive cleavage products the title compound (+)-20 in very high (>99percent) enantiomeric excess.Absolute stereochemistry of the cyclobutanopyrrolidinone, containing three contiguous stereocenters, was confirmed by X-ray crystallography.