B-Ring unsaturated estrogens: biological evaluation of 17α-Dihydroequilein and novel B-Nor-6-thiaequilenins as tissue selective estrogens

The pharmacology and SAR of representative equine estogens is described. 17α-Dihydroequilenin was found to prevent bone loss after 5 weeks of oral administration to ovariectomized rats. The stereochemical significance of the D-ring and the C/D ring juncture was investigated with a series of benzothiophene-based equilenin analogues.