17β-Hydroxy-3-methoxyestra-1,3,5(10)-triene-6,7-dione 7-Oxime

X-ray structure analysis of the title compound, C 19 H 23 NO 4 , showed an unexpected anti orientation for the 6-oxo-7-oximino function. After molecular-mechanics calculations, the H atom of the 17-hydroxy moiety, which participates in a strong hydrogen bond formed in the crystalline state, changed its orientation substantially. Some change in the conformation of ring B was also observed.