Preparation of tritium‐labelled phenethanolamines by catalytic reduction

Tritium-labelled plenethanolamines have been readily prepared by catalytic reduction of corresponding α-aminophenones. Erythro phenethanolamine racemates are exclusively formed by Pd-catalyzed reduction of α-alkyl-α-aminophenones. In one case, an α-aminophenone was further reduced by tritium to the phenethylamine, which has never been observed with catalytic hydrogenation under similar conditions. In this manner, three adrenergic agents have been labelled for metabolism and tissue distribution studies: sotalol-7−3H hydrochloride, soterenol-7−3H hydrochloride, and mesuprine-7−3H hydrochloride.