In 50 ml of tetrahydrofuran was dissolved 8.5 g of the 1α,2α;4α,5α-diepoxy-21,21-dimethoxy-20-methylpregn-6-en-3-one obtained in Example 76, followed by dropwise addition of 100 ml of a 1.0M solution of lithium tri-sec-butylborohydride in tetrahydrofuran under ice-cooling. After completion of dropwise addition, the mixture was stirred at room temperature for 2 hours. The excess reducing agent was decomposed with water and the residual alkylborane was decomposed with alkaline hydrogen peroxide, followed by extraction with ethyl acetate. The extracts were pooled, washed with aqueous sodium chloride solution, and dried over sodium sulfate, followed by concentration under reduced pressure. Recrystallization of the concentrate from ethyl acetate gave 2.90 g of 21,21-dimethoxy-20-methylpregn-6-ene-1α,3β,5a-triol showing the following physical properties.
