[(1S)-3-Methyl-1-[[(2S)-2-methyloxiranyl]carbonyl]butyl]-carbamic Acid 1,1-Dimethylethyl Ester-d3 is the isotope labelled analog of [(1S)-3-Methyl-1-[[(2S)-2-methyloxiranyl]carbonyl]butyl]-carbamic Acid 1,1-Dimethylethyl Ester. [(1S)-3-Methyl-1-[[(2S)-2-methyloxiranyl]carbonyl]butyl]-carbamic Acid 1,1-Dimethylethyl Ester is a reagent in the synthesis of proteasome inhibitor epoxomicin, which has antitumor, antiinflammatory and antibiotic properties.