A solution of 1.5 g of 17-(ethylthio)-9-fluoro-11β-hydroxyandrosta-1,4,16-trien-3-one in 70 ml of dry dichloromethane is stirred with 609 mg of N-chlorosuccinimide at room temperature under a nitrogen atmosphere for 2.5 hours. The resulting solution is diluted with 140 ml of chloroform; the chloroform solution is washed with saturated NaHCO3 solution and water, dried over anhydrous Na2SO4 and evaporated in vacuo to give 1.65 g of a foam. The foam is dissolved in chloroform-hexane (4:1) and chromatographed on a 60 g-silica gel column. Elution with chloroform-hexane (4:1) gives 1.2 g of a tlc-homogenous material. Crystallization from acetone-hexane gives 815 mg of an analytical specimen of the title compound, melting point 240°-241° C. (dec).
