1α,3β-Bis(tert-butyldimethylsilyloxy)-17β-(hydroxymethyl)androst-5-ene (11.0 g) was dissolved in tetrahydrofuran. Under cooling with ice, potassium hydride (30% in oil, 200.3 g) and 18-crown-6 (2.64 g) were added to the solution, which was then stirred for 5 min. 1-Bromo-4-ethyl-4-(triethylsilyloxy)hexane (25.91 g) was then added to the mixture and reacted for 3.5 hours. After stopping the reaction by adding a saturated aqueous ammonium chloride solution, the mixture was extracted with ethyl acetate. The organic layer was dried over anhydrous magnesium sulfate, filtered and the filtrate was evaporated under reduced pressure to remove the solvent. The resulting residue was purified by column chromatography (hexane:ethyl acetate=50:1) to give the titled compound (15.8 g).
