—Pyridium p-toluenesulfonate (6.32 g) was added to a solution of (3β)-3-hydroxypregn-5-en-20-one (1; 100 g) in dichloromethane (600 ml) and ethyl vinyl ether (200 ml). After stirring of the reaction mixture for 1 h at room temperature triethylamine (20 ml) was added, whereupon the mixture was poured into a saturated aqueous solution of sodium hydrogen carbonate (1 l). The product was extracted into dichloromethane; the combined organic phases were washed with brine, dried over sodium sulfate, and concentrated under reduced pressure to give (3β)-3-[(1-ethoxyethyl)oxy]pregn-5-en-20-one (2; 125.6 g), which was used in the following step without further purification.
