Sulfoxides, 1-Sulfones, and 1-Telluroglycosides in Glycosylation Reactions

Further oxidation of 1-thioglycosides leads to glycosyl sulfones. These have been reported to be activable by magnesium bromide etherate in the presence of sodium hydrogencarbonate.167 

1-Telluroglycosides are obtainable by treatment of acylated a-glycopyranosyl bromides with diaryltellurides in the presence of sodium borohydride. Good to excellent yields are obtained of aryl 1-telluro- (3-glycosides having acetyl, benzoyl, or benzyl at the 2,3,4-positions, and acetyl at the 6-position.172 

Electrochemical oxidation of telluroglycosides in the presence of primary or secondary alcohols results in 0-glycosylation.173 

Strong preferential activation of 1 -telluroglycosides is possible in the presence of of the corresponding 1-selenoglycoside by using IV-iodosuccinimide as promoter. This further extends the possibilities for selective glycosylation reactions in oligosaccharide synthesis.175 

Glycosyl fluorides, which have many applications in chemical and biomedical studies, are obtainable by treatment of both 1-seleno- and 1-telluro-glycosides with diethylaminosulfur trifluoride (DAST).176 

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