Sequential determination of sugar units in reducing disaccharides by capillary gas chromatography/Fourrier-transform infrared spectroscopy

Conversion of disaccharide reducing units into the corresponding methoximes followed by their reduction with NaBH₄CN to the corresponding deoxy(methoxyamino)alditol glycosides (RCH₂-NHOCH₃) introduces a constitutional asymmetry in the sugar molecule. After methylation of the resulting compounds, cleavage of the glycosidic bonds is carried out by BF₃- catalyzed methanolysis, affording permethylated O-methylglycosides and permethylated deoxy(methylmethoxyamino)alditols with a free ?OH corresponding to the position of the glycosidic bond. Identification of the reducing moiety is achieved by GC-FTIR and computerized retrieval of library FTIR spectra.