The synthesis of 25-hydroxycholecalciferol-23,23,24,24-t4 of high specific activity

Catalytic tritium reduction of cholest-5-en-23-yne-3beta,25-diol diacetate (VIII) gave cholest-5-ene-3 beta,25-diol diacetate-23,23,24,24-t4 (IX) having a specific activity of 92 Ci/mmol. Bromination, dehydrobromination and hydrolysis of the labelled material gave cholesta-5,7-diene-3beta,25-diol-23,23,24,24-t4 (XI) which was photolyzed to the previtamin and then thermally equilibrated to 25-hydroxycholecalciferol-23,23,24,24-t4 (I).