Oxidation of thioglycosides

A range of other sulfur(IV) and (VI) derivatives formally obtained by the oxidation of thioglycosides have been prepared, but they are apparently not employed to date in O-glycosylation reactions. These include glycosyl sulfenamides and sulfonamides, as well as sulfinates and sulfonates [289]. S-Glycosyl sulfenic acids have been prepared as transients by the syn-elimination of S-(2-cyanoethyl) glycosyl sulfoxides [311]. 

Glycosyl sulfoxides and sulfones are readily prepared by the oxidation of thioglycosides. Sulfoxides are generally formed as diastereomeric mixtures, and the mixture is used without separation of the diastereomers in glycosylation reactions. 

The oxidation of the a-amino acids has not been completely studied, but it appears to be slow in most cases.8-9 The organic sulfide linkage is oxidized by periodate to a sulfone, with the concomitant liberation of iodine,48 but the oxidation of a 1-deoxy-l-thioglycoside, without occurrence of this side reaction, has been carried out at least once (in very dilute solution).44... 

In addition to the standard mCPBA, many oxidants have been applied in the conversion of thioglycosides into glycosyl sulfoxides, including sodium metaperio-... 

Sulfoxides and seienoxides are known to easily undergo beta-elimination reactions. Sugar sulfoxides obtained by oxidation of respective thioglycosides were efficiently transformed to glycals upon heating in toluene (O Scheme 20) [160]. 

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