TBAF tetrahydrofuran → 1alpha,3beta-Dihydroxy-17-(3-hydroxy-3-methylbutylthiomethyl)androsta-5,7,16-triene

1α,3β-Bis(tert-butyldimethylsilyloxy)-17-(3-hydroxy-3-methylbutylthiomethyl)androsta-5,7,16-triene (63.5 mg, 0.0981 mmol), a 1M tetra-n-butylammonium fluoride tetrahydrofuran solution (1 ml) and tetrahydrofuran (1 ml) were subjected to reaction using a procedure similar to that of Example 5(2) (reflux under heating for 5.5 hours), worked up and purified by preparative thin layer chromatography (2 sheets (each 0.5 mm thickness), dichloromethane:ethanol=9:1, developed once) to give the titled compound (39.2 mg, 95%) as a colorless oil.