Enantiospecific tritium labeling of 28-homocastasterone

A regiospecific and enantiospecific synthesis of tritium-labeled 28-homocastasterone is reported. Appropriate chlorocarbonate, efficiently synthesized from the starting 28-homocastasterone in an overall yield of 46%, undergoes catalytic tritium dechlorination by the T₂ /Pd[0]/Et₃ N system, providing 28-[3β-³ H]homocastasterone, in a good yield, radiochemical purity (>97%), and with a high specific activity (5.8 Ci/mmol).