Isolation and Characterization of Atropisomers of Seven-Membered-Ring Benzolactams

The atropisomeric properties of seven-membered-ring benzolactams (7ac and 8a) [1,5-benzodiazepin-2-one (a), 1,5-benzothiazepin-4-one (b), and 1-benzazepin-2-one (c)] were examined. The atropisomers were isolated as the diastereomers with an (S)-phenethylamide moiety, which were characterized by X-ray crystallography, and the barriers to their interconversion were clarified.