[[(3beta)-25-[[(1,1-Dimethylethyl)dimethylsilyl]oxy]cholesta-5,7,16-trien-23-yn-3-yl]oxy]dimethyl (1,1,2-trimethylpropyl)silane → (3beta)-Cholesta-5,7,16-trien-23-yne-3,25-diol

Participants

Reaction Steps

To a solution of 114 g (131 mmol) crude [[(3β)-25-[[(1,1-dimethylethyl)dimethylsilyl]oxy]cholesta-5,7,16-trien-23-yn-3-yl]oxy]dimethyl(1,1,2-trimethylpropyl)silane in 500 mL of THF was added 200 g (765 mmol) tetrabutylammonium fluoride hydrate with the aid of 500 mL of THF. After stirring at room temperature for 18 hr., the mixture was diluted with 500 mL of ethyl acetate and 500 mL of 10% aqueous ammonium chloride. The aqueous layer was extracted twice with 500 mL each of ethyl acetate. The combined organic layers were washed with 500 mL of 10% aqueous ammonium chloride, 500 mL of water, and 500 mL of brine. The organic layer was dried over MgSO4 and concentrated to a total weight of 525 g. The resulting suspension was stirred at room temperature for 2 hr and then stored in a freezer overnight. The solid was filtered, washed with cold ethyl acetate, and air-dried for 2 hr to give 27.8 g of crude (3β)-cholesta-5,7,16-trien-23-yne-3,25-diol. This was suspended in 270 mL of methanol and the mixture was refluxed for 10 min. Then, 55 mL water was added dropwise over 10 min. The suspension was stirred at 60° C. for 1 h, and stored in a refrigerator overnight. The precipitate was filtered, washed with cold 100 mL 50% aqueous methanol, and dried in a vacuum oven at 45° C. to give 25.4 g (49.1% over four steps) of (3β)-cholesta-5,7,16-trien-23-yne-3,25-diol as white crystals: mp 185°-192° C. Anal. Calcd. for C27H38O2 : C, 82.18; H, 9.71. Found: C, 81.93; H, 9.74.

Provenance & Evidence