Abstract Syntheses of the labelled oxidative metabolites of acrylamide and acrylonitrile– reference compounds for the evaluation of human exposure to important toxicants–are reported. For that, L-cystine tert-butyl ester was acetylated and the product reductively cleaved to L-cysteine tert-butyl ester, which reacted with carbamoyl [D 3] oxirane (obtained from [D 3] acrylonitrile and 30% aq. H 2 O 2 at pH= 7.0–7.5) and afforded a separable ...