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

Participants

Reaction Steps

To a mixture of 70.5 mL (262 mmol) tributyltin hydride and 1.08 g (6.55 mmol) 2,2'-azobis(2-methylpropionitrile) (AIBN) in 50 mL of hexane at 80° C. was added a solution of 117 g (131 mmol) crude phenyl-carbamothioic acid O-[(3β)-25-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-3-[[dimethyl(1,1,2-trimethylpropyl)silyl]oxy]cholesta-5,7,16-trien-23-yn-22-yl] ester in 1.5 L of hexane over 45 min. After refluxing for 1 hr, additional tributyltin hydride (35 mL, 131 mmol) and AIBN (1.07 g, 6.52 mmol) were added. After 30 min. of refluxing, the mixture was cooled to room temperature and stirred for 1 hr. The precipitate was filtered, and the filtrate was concentrated. The residue was dissolved in 200 mL of hexane and purified by filtration through 425 g of silica gel. The column was eluted with hexane and then with 20% toluene in hexane. The fractions containing the product were combined and concentrated to give 114 g (overweight) of crude [[(3β)-25-[[(1,1-dimethylethyl)dimethylsilyl]oxy]cholesta-5,7,16-trien-23-yn-3-yl]oxy]dimethyl(1,1,2-trimethylpropyl)silane as a light yellow oil. This crude material was used in the next step. An analytical sample was obtained by chromatographic purification followed by crystallization from ethyl acetate/methanol (1:1): mp 62°-66° C.; Anal Calcd. for C41H70O2Si2 : C, 75.62, H, 10.84; Si, 8.63. Found C, 75.12; H, 10.77; Si, 8.55.

Provenance & Evidence