Sodium borohydride → 1alpha,3beta-bis(tert-butyldimethylsilyloxy)-20(R)-hydroxypregna-5,7,16-triene

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Reaction Steps

To a solution of 1α,3β-bis(tert-butyldimethyl-silyloxy)-20-oxopregna-5,7,16-triene (93 mg, 0.167 mmol) and cerium (III) chloride heptahydrate (93 mg, 0.251 mmol) in methanol (1.5 ml) and tetrahydrofuran (6 ml) cooled at 0° C. was gradually added sodium borohydride (32 mg, 0.835 mmol). The reaction solution was stirred at room temperature for one hour, then concentrated under reduced pressure and the residue was taken into water and extracted with ethyl acetate. The organic layer was washed with brine and then dried over magnesium sulfate, and the solvent was distilled off under reduced pressure. The resulting residue was purified by preparative thin layer chromatography (0.5 mm×2, hexane:ethyl acetate=10:1, developed three times) to give the title compound as a colorless solid (68.2 mg, 73%) and 1α,3β-bis(tert-butyldimethylsilyloxy)-20(S)-hydroxypregna-5,7,16-triene (17.0 mg, 18%).

Provenance & Evidence