A new retro-aza-ene reaction: Formal reductive amination of an α-keto acid to an α-amino acid

Article abstract of DOI:10.1016/S0040-4020(01)88730-5

Two diastereomeric reductive amination reagents, 1a and 1b, were synthesized. Each reagent was condensed with ethyl pyruvate as a model α-keto acid. Flash vacuum pyrolysis of the pyruvate adducts, 10a and 10b, results in cheleotropic elimination of CO, followed by a new type of retro-aza-ene reaction. A molecule of benzene and a protected alanine derivative, 11, are produced in the retro-ene reaction. This sequence constitutes the first formal more readily than distereomer 10a, indicating that an exo transition state is preferred over an endo transition state for this particular retro-aza-ene reaction.