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.