Tetrabutylammonium Fluoride → 1alpha,3beta-dihydroxy-20(R)-{(Z)-(4-ethyl-4-hydroxy-2-hexenyloxy)}pregna-5,7,16-triene

By the same procedure as in Example 9, 1α,3β-bis(tert-butyldimethylsilyloxy)-20(R)-{(Z)-(4-ethyl-4-triethylsilyloxy-2-hexenyloxy)}pregna-5,7,16-triene (82.0 mg, 0.103 mmol), tetrahydrofuran (3 ml) and 1M tetra-n-butylammonium fluoride solution in tetrahydrofuran (2 ml) were reacted (heating under reflux for 5.5 hours) and worked up, and then the residue was purified by preparative thin layer chromatography (0.5 mm×1, dichloromethane:ethyl acetate:ethanol=20:80:1, developed once) to give the title compound as a white solid (46.1 mg, 98%).