Successive treatment of N-acylsultams 3 with NaN(TMS)₂, l-chloro-1-nitrosocyclohexane (1) and 1N aq. HCl gave diastereomerically pure, crystalline Nhydroxyamino acid derivatives 4. Products 4 were converted to various amino acids 6, an NBOC-amino acid 8 and to N-hydroxyamino acids 9. (S,S)-Isoleucine (16) was obtained from N-crotonoylsultam 13 via an organomagnesium- 1,4-addition/enolate trapping process generating two stereogenic centers.