X-Ray Crystallographic and Proton Nuclear Magnetic Resonance Studies of β-Hydroxy-N-nitrosamines derived from α-Amino Acids and Ephedrine

β-Hydroxy-N-nitrosamines derived from l-leucine, l-valine, l-phenylalanine, d-phenylglycine and (1R,2S)-ephedrine have been synthesized and analyzed. These compounds all exhibit rotameric populations of (E)- and (Z)-stereoisomers that are a result of the barrier to rotation about the N-nitroso (N–NO) group. A correlation is made between the X-ray crystallographic data of the N-nitroso-ephedrine derivative 6 and the 1H NMR of the N-nitrosamines 4a–4d. From this comparison, the identities and ratios of (E)- and (Z)-rotamers were unambiguously assigned. Finally, the 1H NMR also provides some insight into the conformational changes that occur when the nitrosamine rotamers interconvert.