THE STRUCTURE OF 17-BETA-EPOXY-17-ALPHA-PREGN-5-EN-3-BETA-OL-20-ONE MONOHYDRATE

The structure of the title compound (1) has been studied by means of X -ray diffraction. The region of cycle D in epoxide 1 was compared with that of the 16,17 alpha-epoxy derivatives of progesterone and pregnen olone (studied previously) as well as with that of the respective 16,1 7 alpha- and 16,17 beta-cyclopropano analogs. In contrast to the 16,17 alpha-epoxy-20-oxo derivatives, in compound 1 the electron conjugatio n of the epoxide ring with the CH3CO group at C(17) is partly disrupte d. Moreover, the steric congestion at C(17) is significantly less pron ounced inn 16,17 beta-epoxide 1 than in its 16,17 alpha-counterpart. B oth of these factors, especially steric decongestion, are favorable fo r nucleophilic attack at C(17) in the molecule of 1. The X-ray diffrac tion data do not contradict the previously advanced mechanism of epoxi de ring opening in 16,17 alpha- and 16,17 beta-epoxy-20-oxo steroids b y nucleophilic reagents.