Synthesis of (R)‐(+)‐3H‐etomidate

Etomidate, (R)-(+)-ethyl-1-(1-phenylethyl)-1H-imidazole-5-carboxylate, is a short-acting hypnotic. A new synthesis, featuring optical resolution on a non-radioactive precursor and introduction of the tritium label by reductive dehalogenation, is described. The title compound was obtained at a specific activity of 3.77. Ci/mmol and a 99.9 % HPLC purity.