Synthesis and estrogenic properties of 17-epi-ethynylestradiol and its ether derivatives epimestranol and epiquinestrol

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Abstract
The synthesis of 17-epi-ethynylestradiol (10), the 17.beta.-ethynyl-17.alpha.-ol epimer of the well-known orally active estrogen, ethynylestradiol, was achieved by LiAlH4 reduction of epoxide as well as by demethylating epimestranol (11) with CH3MgI. Compound 11 was obtained by the unusual 17.beta.-ethynylation of estrone 3-methyl ether under equilibrating conditions. The in vitro rabbit uterine estrogen receptor-binding affinity and the oral estrogenicity in the rat for the 17-epi compounds 10, 11 and 20 (epiquinestrol) was evaluated. Despite moderate estrogen receptor-binding affinity, compound 10 was devoid of measurable estrogenicity at 10 mg/kg or antiestrogenicity at 3 mg/kg.