N-Methylsuccinimide-d3 is the isotope labelled analog of N-Methylsuccinimide (M329425); a model compound used to investigate the mechanism of enolization step by density-functional theory (DFT) calculations. N-Methylsuccinimide is a metabolite of N-methyl-2-pyrrolidone (NMP) and its presence in plasma and urine can be used as a biomarker of exposure to NMP