PMR and CMR spectroscopy of methyl 2,3,4,6-tetra-O-methyl-α and β-D-glucopyranoside : An application to the identification of partially methylated glucoses

Abstract

The proton and 13C magnetic resonance spectra of methyl 2,3,4,6-tetra-O-methyl-alpha and -bêta-D-glucopyranoside are completely assigned. For this purpose specific deuterium and 13C labelling, spin decoupling and spectrum simulation are employed. The NMR data are discussed and compared with those of the free monomers and the methylglucosides. A partially methylated glucose obtained as a degradation product in the permethylation analysis of a carbohydrate can be identified after permethylation of the compound with labelled Me groups and comparison of the PMR or CMR spectra with those of reference permethylglucoses. From these spectra information is obtained about type and ring form of the monomers and position(s) of the glycosidic bond(s) in the original oligo- or polysaccharide. The number of reference compounds necessary for identification is strongly reduced. The method can be extended to other monomers because there are significant differences between the NMR data of the various permethylmonosaccharides.