The chemical synthesis of glutamic acid specifically labelled with deuterium or tritium in the alpha or 2 position

Glutamic acid specifically labelled with isotopic hydrogen in the 2 position was produced by exchange equilibration with labelled protons during the reaction of acetylglutamic acid with acetic acid and acetic anhydride. The position of label was established by n.m.r. and mass spectrometry of the deuterium‐labelled compound, and by transaminase‐catalyzed exchange with protons in the case of tritium‐labelled compound. The specific and complete exchange obtained in our experiments contrasts with the previously reported virtual nonlabelling under somewhat different conditions in which the presumed azlactone enolized and hydrolysed in an aqueous medium.