HIGH SPECIFIC ACTIVITY-STEROIDS .2. MICROSCALE SYNTHESIS OF NORGESTREL-[9,11-H-3]

The synthesis of the high specific activity (39 Ci/mmole) tritium labelled steroid norgestrel is described. A practical synthesis of the required substrate for tritium incorporation, 18-methyl-DELTA9(11)-estradiol-3-methyl ether (6), was developed from norgestrel itself. Following reduction with carrier-free tritium gas, microscale conditions were employed for the conversion of the resulting labelled intermediate (7) back to norgestrel-[9,11-H-3], including a selective in situ protection of the A-ring ketone of 19-norandrost-4-ene-3,17-dione (11).