ChemInform Abstract: Stereospecific Preparation of γ‐Lactam Derivatives via Ring Expansion of cis and trans β‐Lactam Derivatives: α‐Substituent Effect of β‐Lactam Derivatives.

Abstract In the case of aryl substituents in trans or cis β‐lactam derivatives, only the trans γ‐lactam derivative is obtained, whereas trans or cis β‐lactams with alkyl substituents lead to the corresponding trans or cis γ‐lactam, respectively.