Potassium ethanethioate → 17-Acetylthiomethyl-1alpha,3beta-bis(tert-butyldimethylsilyloxy)androsta-5,7,16-triene

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Reaction Steps

To a solution of 1α,3β-bis(tert-butyldimethylsilyloxy)-17-(hydroxymethyl)androsta-5,7,16-triene (100 mg, 0.183 mmol), triphenylphosphine (96.0 mg, 0.366 mmol) and imidazole (49.8 mg, 0.732 mmol) in dichloromethane (2 ml), N-bromosuccinimide (65.1 mg, 0.366 mmol) was added at 0° C. and stirred at room temperature. After 1 hour, hexane was added to the reaction mixture, which was then washed with water and saturated aqueous sodium chloride. After drying over anhydrous magnesium sulfate, the solvent was removed under reduced pressure to give a mixture (150 mg) containing 1α,3β-bis(tert-butyldimethylsilyloxy)-17-(bromomethyl)androsta-5,7,16-triene. This mixture was dissolved in acetone (1.5 ml), followed by addition of potassium thioacetate (31.4 mg, 0.275 mmol) and stirring for 30 minutes. The reaction mixture was diluted with hexane and filtered. The resulting filtrate was evaporated under reduced pressure to remove the solvent and the residue was purified by preparative thin layer chromatography (0.5 mm×2 plates, hexane:ethyl acetate=20:1, developed once) to give the titled compound (70.2 mg, 64%) as a colorless oil.

Provenance & Evidence