16 alpha-Hydroxy-20-oxopregn-5-en-3 beta-yl acetate

In the title compound, C23H34O4, the two saturated six-membered rings have slightly flattened chair conformations and the unsaturated ring assumes a 8 beta ,9 alpha -half chair conformation distorted towards a 8 beta -sofa. T he five-membered ring has an unusual conformation close to a 13 beta -envel ope. The acetoxy and methyl ketone substituents are twisted with respect to the average molecular plane of the steroid nucleus. The molecules are hydr ogen-bonded head-to-head via the hydroxy and methyl ketone groups forming d imers, which are stacked in planes perpendicular to the b axis.