To a stirred solution of 4β-ethylandrostan-3α,6α,17β-triol (Preparation 11, 237 mg) in dioxane (5.8 ml), water (1.08 ml), pyridine (0.1 ml) and NBS (249 mg) were added. After 72 h, EtOAc (70 ml), H2O (30 ml) and 10% Na2SO3 aqueous solution (24 ml) were added and the mixture was stirred for 10 min. The phases were separated and the aqueous phase was extracted with EtOAc. The combined organic extracts were washed with of 5% aqueous NaHCO3, brine, dried over MgSO4, filtered and evaporated to dryness. The crude product was purified by flash chromatography (SiO2, EtOAc/n-hexane 70/30) to give the title compound as a white solid (135 mg, 57%).
