AN EFFICIENT GLYCOSYLATION REACTION OF 1-HYDROXY SUGARS WITH VARIOUS NUCLEOPHILES USING A CATALYTIC AMOUNT OF ACTIVATOR AND HEXAMETHYLDISILOXANE

In the presence of hexamethyldisiloxane and anhydros calcium sulfate, a catalytic amount of activator such as tin(II) trifluoromethanesulfon ate, ytterbium trifluoromethanesulfonate, lanthanum trifluoromethanesu lfonate or tin(II) chloride smoothly promotes the glycosylation reacti ons between 1-hydroxy sugars and free alcohols, electron-rich aromatic compounds or silylated nucleophiles to produce various O-, C- or N-gl ycosides stereoselectively in high yields. In the case of oxygen or ni trogen nucleophiles, beta-ribosides are formed, except that alpha-ribo sides are obtained predominantly in the presence of lithium perchlorat e. In the case of carbon nucleophiles such as electron-rich aromatic c ompounds or silyl enol ethers derived from carbonyl compounds, perfect beta-selectivity is shown either in the the presence or absence of li thium perchlorate. Further, pyranosyl substrates such as glucose or ga lactose afford the corresponding alpha-anomers, except with electron-r ich aromatic compounds.