Synthesis of tritiated β‐(S‐benzylmercapto)‐β,β‐cyclopentamethylene propionic acid

β‐(S‐benzylmercapto)‐β,β‐cyclopentamethylene propionic acid has been tritium labeled in the cyclohexyl ring. A key feature of the synthesis is the reduction of phenolwith tritium gas over catalyst giving tritiated cyclohexanone. A Wadsworth‐Emmons reaction followed by esterase hydrolysis of the resulting ester and Michael addition of p ‐methylbenzylmercaptan afford the title compound.