Imidazole → (1alpha,3beta)-3-[[Dimethyl(1,1,2-trimethylpropyl)silyl]oxy]-1-[(triethylsilyl)oxy]androsta-5,7-dien-17-one

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Reaction Steps

A 3-L three-necked flask equipped with a mechanical stirrer, addition funnel, and Ar-inlet tube was charged with 60.1 g (199 mmol) of (1α,3β)-1,3-dihydroxyandrosta-5,7-dien-17-one, 40.7 g (598 mmol) of imidazole, and 400 mL of dichloromethane. After cooling with an ice-water bath for 5 min., 50.7 mL (257 mmol) of thexyldimethylsilyl chloride was added over 12 min. The cold bath was removed, and the mixture was stirred at room temperature for 5 hr. After cooling again with an ice-water bath. 36.8 mL (219 mmol) of triethylsilyl chloride was added over 10 min. After stirring at room temperature overnight, 220 mL of hexane was added. After 15 min, the precipitate was removed by filtration and washed with 2×120 mL of hexane. The combined filtrate and washes were concentrated, and the residual hexane was removed by co-evaporation with 120 mL of methanol, and the suspension was stirred for 2 hr in order to obtain a powdery material. After the suspension was stored in a refrigerator overnight, the precipitate was filtered and washed with 2×160 mL of 95% methanol. Drying under high vacuum afforded 96.8 g of (1α,3β)-3-[[dimethyl(1,1,2-trimethylpropyl)silyl]oxy]-1-[(triethylsilyl)oxy]androsta-5,7-dien-17-one as a beige solid.

Provenance & Evidence