Chemical Synthesis, 17β-Hydroxysteroid Dehydrogenase Type 1 Inhibitory Activity and Assessment of In Vitro and In Vivo Estrogenic Activities of Estradiol Derivatives

17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) was chosen as a key steroidogenic target enzyme to reduce the formation of estradiol (E2), which is the most potent estrogen. This article completes a previous study by synthesizing and testing 16β-methylene derivatives (Br, Cl and OH) of E2 in order to generate new structure-activity relationships. This study also investigates a series of 2-methoxy (MeO) derivatives synthesized as non-estrogenic inhibitors of 17β-HSD1. The 2-MeO-E2 derivatives (16β-CH2Br, 16β- CH2OH and 16α-(CH2)3Br) are all less potent inhibitors (IC50 = 5.91, 3.80 and 5.80 μM) than analogues without the 2-MeO group (IC50 = 1.20, 1.27 and 0.99 μM, respectively) for the reduction of estrone into E2 by 17β-HSD1 overexpressed in HEK-293 cells. Except for one compound, these E2 derivatives have shown an estrogenic-like effect on estrogen-sensitive T-47D cells at 1 μM. A cytotoxic effect was also obtained at higher concentrations for two compounds tested on T-47D cells. However, no estrogenic-like effect was observed in the estrogen-sensitive tissues (uterus and vagina) of the ovariectomized mouse model for 2-MeO- 16α-bromopropyl-E2.