An easy access to halide ion-catalytic alpha-glycosylation using carbon tetrabromide and triphenylphosphine as multifunctional reagents.

Yuko Shingu, Yoshihiro Nishida, Hirofumi Dohi, Kazukiyo Kobayashi

Index: Org. Biomol. Chem. 1(14) , 2518-21, (2003)

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Abstract

The reaction of a 2-O-benzyl-1-hydroxy sugar with CBr4 and Ph3P generates a glycosyl bromide in situ, which is coupled with an acceptor alcohol in the presence of N,N-tetramethylurea to afford an alpha-glycosyl product virtually quantitatively. In a proposed pathway, the reagent combination plays multiple roles such as the generation of a glycosyl donor, the activation of glycosylation, and the dehydration of the reaction system. These roles allow a simple alpha-glycosylation to be performed without special attention to dehydration. Various alpha-glycosyl (D-gluco-, D-galacto- and L-fuco-) products including glycosyl glycerols and cholesterols have been prepared with this method.