Synthesis of 17α ‐ethynylestradiol‐6, 7‐³H and 17α‐ethynylestradiol‐6,7‐³H, 3‐cyclopentyl‐1‐¹⁴C ether

Abstract Several authors have reported on the physiological differences between 17α‐ethynylestradiol and its 3‐cyclopentyl ether. The radiolabeled steroids were required to compare their relative absorptions, excretions, and metabolic products. Tritium was introduced into the steroid nucleus by catalytic tritiation of 6‐dehydroestrone. Etherification with either cyclopentyl bromide or cyclopentyl‐ 14 C p‐bromobenzenesulfonate gave the cyclopentyl ether of estrone. Ethynylation of either estrone‐6, 7‐ 3 H or its cyclopentyl‐ 14 C ether gave 17α‐ethynylestradiol‐6, 7‐ 3 H and 17α‐ethynylestradiol‐6, 7‐ 3 H, 3‐cyclopentyl‐ 14 C ether. It was also possible to etherify 17α‐ethynylestradiol directly although in poorer yields.