High specific activity steroids I: 17α‐ethynylestradiol‐[9,11‐3H] and norethindrone‐[9,11‐3H]

We report herein the first high specific activity tritium labelled synthesis of the widely used oral antifertility agents ethynylestradiol (5) and norethindrone (9). These substances were prepared at a specific activity of 54 Ci/mmol, a figure which is 48 and 377 times greater than any previously described preparations of (5) and (9) respectively. Microscale conditions were developed for all the steps in the sequence, including the Birch reduction (1), so that the initially high level of enrichment usually achieved in the reduction of Δ9(11)-estradiol 3-methyl ether was retained in the final products.