Steroids CCLXXII(1). Biologically-active labile ethers III(2). A new class of potent estrogens

Abstract Possible structural modifications for increasing the sensitivity of steroid ethers are discussed. 3-Methoxyestra-1, 3, 4 (10)-trien-17-one cyclic ethylene ketal and cyclic ethylene monothioketal suffer cleavage of the ketal ring on exposure to a combination of either lithium aluminum hydride and aluminum trichloride, or diborne and boron trifluoride. The resultant 17μ-(2-hydroxyethyl) ether and thioether have been ceonverted into a range of new estrane derivatives, several of which show pronounced estrogenic activity by the oral route of administration. Other 17-ketals also undergo cleavage to form 17μ-ethers.