Reductive cleavage of glycosides with borane complexes in the presence of boron trifluoride etherate

Mixtures consisting of five equivalents each of borane.methyl sulfide and boron trifluoride etherate per equivalent of acetal or five equivalents of various amine-borane complexes and 10 equivalents of boron trifluoride etherate readily accomplished reductive cleavage of the glycosidic linkages of several per-O-methylated monosaccharides and polysaccharides. In all cases, the expected products were obtained in the expected molar proportions and no artifactual products were observed. Reductive-cleavage analysis using these reagents is particularly convenient because the reagents themselves are easy to handle and because subsequent acetylation of the products is accomplished in situ.