Add time:09/24/2019         Source:sciencedirect.com

The relative reactivities of the hydroxyl groups of methyl α- and β-D-xylopyranosides in selective sulfonylation reactions with methanesulfonyl chloride in pyridine have been determined. For the α-anomer, the order of reactivity is O-2> O-4>O-3, and for the β-anomer O-4>O-3>O-2. Useful yields of mono- or disubstituted xylosides can be obtained from both anomers by suitable choice of reactant ratios and the structures of the major products have been established. Reports that the hydroxyl groups of benzyl α-D-xylopyranoside and benzyl α-D-glucopyranoside show orders of reactivity different from those of the corresponding methyl glycosides have been found to be erroneous. The correct structures of the major products formed by selective p-toluenesulfonylation of benzyl α-D-xylopyranoside and by selective methanesulfonylation and lauroylation of benzyl α-D-glucopyranoside have been established by synthetic routes.

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