Nuclear Magnetic Resonance Spectroscopic Approaches for the Determination of Interglycosidic Linkage and Sequence in Oligosaccharides

Abstract

The potential of various one-and two-dimensional nuclear magnetic resonance spectroscopic methods in deducing information about the interglycosidic linkage and sequence of monosaccharide residues in oligosaccharides is presented and the different techniques are evaluated.

Structure elucidation and immunological activity of a novel polysaccharide from the fruit bodies of an edible mushroom, Sarcodon aspratus (Berk.) S. Ito.

“…The signal at ı 4.54, ı 4.52, ı 4.74, ı 4.78, ı 4.53 in the 1 H NMR spectrum, were assigned to the anomeric protons of Residues A, B, C, D, E (Rds A-E), respectively, However, only one anomeric carbon signal at around ı 103.7 can be observed in the 13 C NMR spectrum, which confirmed that all the residues in HBP are ofˇconfiguration, and in its high magnetic field, C-3 signals of Rds B and C were both downshifted to ı 85.0; C-4 signal of Rd D was downshifted to ı 81.0 due to the ␣ effect of glycosylation [21]. Same effect happened to r C-6 of Rds A and B that downshifted to ı 69.6, ı 68.8 respectively.…”

Structure of Galactosylononitol

“…If the linkage site was at carbon C-5, such an NOE cross-peak would not be possible. Further evidence was provided by a long-range 1 H− 13 C connectivity experiment (ge-HMBC), in which three-bond coupling constants across the glycosidic linkage do not depend on conformation . In compound 1 , long-range couplings were observed between H-1‘ and C-3 and between H-3 and C-1‘, respectively (Figure ).…”

“…Additionally, there was a strong cross-peak between H-1‘ and H-2. It is only possible to observe an NOE interaction between the glycosidic anomeric proton and the proton on the carbon adjacent to the linkage site, if that proton is equatorial, − which apparently is only the case for H-2 in compound 1 . This provides strong evidence for the position of the linkage site to be at C-3.…”

“…Further evidence was provided by a long-range 1 H- 13 C connectivity experiment (ge-HMBC), 7 in which three-bond coupling constants across the glycosidic linkage do not depend on conformation. 11 In compound 1, long-range couplings were observed between H-1′ and C-3 and between H-3 and C-1′, respectively (Figure 1). This provides unambigous proof of the position of the galactosyl residue to be attached to carbon C-3 of the ononitol ring.…”

Multiple-Stage Tandem Mass Spectrometry for Structural Characterization of Saponins

“…4 In principle, the complete structure of a saponin can be deduced from NMR data. [9][10][11][12][13] However, application of other techniques may facilitate significantly the assessment of some features, and in practice, a combination of chemical and instrumental methods is used. The tools most frequently used are NMR, MS, and chemical methods.…”