Under the same conditions as in Example 3, 1α-(tert-butyldimethylsilyloxy)-3β-hydroxy-20(S)-phenoxycarbonylthiopregna-5,7,16-triene (33.0 mg, 0.0568 mmol), (Z)-1-bromo-4-ethyl-4-triethylsilyloxy-2-hexene (91.0 mg, 0.284 mmol), tetrahydrofuran (0.5 ml) and 1M KOH solution in methanol (0.5 ml) were reacted and worked up, and then the residue was purified by preparative thin layer chromatography (0.5 mm×1, hexane:ethyl acetate=2:1, developed once) to give the title compound as a pale yellow oil (23.8 mg, 60%).
