In 70 ml of dichloromethane are dissolved 3.0 g of 16β-ethyl-17β-hydroxy-4-estren-3-one and 1.6 ml of N,N-dimethylaniline and, with stirring, 1.2 ml of α-bromopropionyl bromide is added to the above solution. The mixture is stirred at room temperature (15°-25° C.) for 30 hours followed by addition of 300 ml of ethyl acetate. The mixture is washed with 10% sulfuric acid and saturated aqueous sodium chloride solution in that order and dried over anhydrous magnesium sulfate. The solvent is then distilled off under reduced pressure and the residue is subjected to column chromatography. Following passage of 300 ml of diisopropyl ether-n-hexane (1:1), elution is carried out with 600 ml of diisopropyl ether. The eluate is evaporated under reduced pressure to remove the solvent, giving 2.7 g of the above-identified compound as a light-yellow viscous oil.
