Abstract
Regioselective one-pot O-silylation reactions of 1,2-O -isopropylidene-α-d -glucofuranose and 1,2-O -isopropylidene-β-d -fructopyranose using bulky oligosilyl groups are described. Some new silylating reagents (oligosilyl bistriflates), which were generated in situ from readily available phenylsilanes, resulted in 5,6-O -(glucofuranose) and 4,5-O -bridged (fructopyranose) carbohydrates with favoured seven- and eight-membered rings. In these cyclic oligosilyl diethers, three and four ring atoms, respectively, are Si atoms. It is noteworthy, that the seven-membered ring of 5,6-O -[2,4-bis(trimethylsilyl)-1,1,1,3,3,5,5,5-octamethylpentasilan-2,4-diyl]-1,2-O -isopropylidene-α-d -glucofuranose was expanded to an eight-membered ring by regioselective insertion of aerial oxygen into one of the Si-Si bonds. X-ray analyses of some derivatives are presented.
Key words
silyl triflates - bridging protecting groups - carbohydrates - hydrodesilylation
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