Preparation of tritium‐labeled 4‐hydroxy‐α‐[p‐(2‐(N‐pyrrolidinyl) ethoxy) phenyl]‐α′‐nitrostilbene (CN‐928), a biologically‐important metabolite of the antiestrogen CI‐628

3‐³H‐4‐hydroxy‐α‐[p‐(2‐(N‐pyrrolidinyl)ethoxy)phenyl]‐α'‐nitro‐stilbene (³H‐CN‐928), a tritium‐labeled metabolite of the Park‐Davis antiestrogen CI‐628, was prepared by catalytic hydrogenolysis of the corresponding 3‐iodo‐CN‐928 with carrier‐free tritium gas. The precursor was prepared either by iodination of CN‐928, or by total synthesis from 3‐iodo‐4‐hydroxybenzoic acid. The final material was obtained with a specific activity of 22 Ci per mmole, which is sufficiently high for receptor binding studies.