1.7 g. of diphenyldiselenide is dissolved in 90 ml. of absolute ethanol and mixed at room temperature with 480 mg. of sodium borohydride. After decolorization of the yellow solution, 2.2 g. of 3-acetoxy-16α,17α-epoxy-1,3,5(10)-estratriene [V. Prelog et al., Helv. 28, 250 (1945)] is added thereto and the mixture heated for 20 hours under reflux. After cooling to 0° C., 5 ml. of 30% H2O2 is added dropwise, and the solution is gradually warmed to 50° C. The product is worked up in accordance with Example 3, and then an after-acetylation is carried out in 5 ml. of pyridine with 2.5 ml. of acetic anhydride. The reaction solution is introduced into ice water. The thusprecipitated product is vacuum-filtered, washed with water, dissolved in methylene chloride, and dried over sodium sulfate. By chromatography of the crude product on silica gel with acetone/hexane, 930 mg. of 3-acetoxy-1,3,5(10),15-estratetraen- 17α-ol is obtained.
