Successive treatment of N-acylsultams 3 with sodium hexamethyldisilazide, 1-chloro-1-nitrosocyclohexane (1), and aq. HCl gave diastereoisomerically pure, crystalline N-hydroxyamino-acid derivatives 5. These were converted into various amino acids 7, N-hydroxyamino acids 8, and an N-Boc-amino acid 9. (S, S)-Isoleucine (17) and (S, S)-2-acetamido-3-phenylbutyric acid (23) were obtained from N-crotonoylsultam 15 via 1,4-addition of an organomagnesium or organocopper reagent followed by enolate ‘amination' with 1.