Efficient synthesis of ω-mercaptoalkyl 1,2-trans-glycosides from sugar peracetates

Lewis acid-promoted reactions of peracetylated sugars (glucose, galactose, maltose, lactose) with ω-bromo-1-alkanols (C8, C12) were investigated. ZnCl2 was found to promote the 1,2-trans-glycosylation of the alcohols in toluene at about 60 °C in a stereocontrolled manner with better yields than commonly employed promoters such as SnCl4. The ω-bromoalkyl acetylated glycosides were readily converted to ω-mercaptoalkyl glycosides, which are useful for the preparation of glycoclusters.

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