Use of the anomeric centre as an electrophilic species

Employing traditional glycosylation techniques, and exploiting the nature of carbon based nucleophiles to attack from the a-face, the C-glycoside (28) was prepared in 50% yield with good 10 1 a/(3 stereoselectivity. The incorporation of 

Highly stereoselective C-aUylation of glycopyranosides with allylsilanes, catalysed by silyl triflate or iodosilane [48]. 

Notes and discussion. Methyl a-D-gluco- and mannopyranosides and a-D-glycopyranosyl chlorides can react with allylsilanes via activation with trimethylsi-lyl trifluoromethanesulfonate or iodotrimethylsilane to stereoselectively afford the corresponding a-C-allylated glycopyranosides in excellent yields. The yields of the reactions depend on the solvent and the amount of catalyst employed. Acetonitrile is the most suitable solvent whereas dichloromethane, the most commonly used solvent for allylation reactions using allylsilanes, does not afford satisfactory results. The reactions proceed very slowly when promoted by less than 5 mol% of the catalyst, however, the use of 50 mol% of catalyst is sufihcient to force the reactions to completion. 

6-Tetra-O-benzyl methyl a-D-glucopyranoside (1 equiv.) treat as harmful 

Round-bottomed flask with rubber septum plus magnetic stirrer bar 

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