Steroid structure and function VII. remarkable estrogenicity of 3-hydroxy-9 beta-estra-1,3,5(10)-triene-11,17-dione

Remarkably high estrogenic activity was observed for 3-hydroxy-9 beta-estra-1,3,5(10)-triene-11,17-dione despite its unusual bent conformation. The 9 alpha epimer of this compound has markedly less activity despite the fact that its overall shape is nearly identical to that of estrone. The potency of these compounds in enhancing uterine weight in Fischer rats and reducing ovarian weight in parabiosed rats was compared with that of estrone, and the structures were unambiguously identified by X-ray crystallographic study. The results underscore the importance of the phenolic ring A to estrogenic activity, and suggest a tolerance of the putative estrogenic receptor to flexibility in overall molecular shape.