THE STRUCTURE OF 16,17-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 pregnenolone (studied previously) as well as with that of the respective 16,17 alpha- and 16,17 beta-cyclopropano analogs. In contrast to the 16,17 alpha-epoxy-20-oxo derivatives, in compound 1 the electron conjugation of the epoxide ring with the CH3CO group at C(17) is partly disrupted. Moreover, the steric congestion at C(17) is significantly less pronounced inn 16,17 beta-epoxide 1 than in its 16,17 alpha-counterpart. Both of these factors, especially steric decongestion, are favorable for nucleophilic attack at C(17) in the molecule of 1. The X-ray diffraction data do not contradict the previously advanced mechanism of epoxide ring opening in 16,17 alpha- and 16,17 beta-epoxy-20-oxo steroids by nucleophilic reagents.