A fundamental problem in the determination of molecular structure by n.m.r. spectroscopy is insufficient experimental constraints. This problem is particularly marked for oligosaccharides, where few constraints are available across glycosidic linkages. By calculating distances as a function of dihed
The nuclear overhauser effect and structural factors determining the conformations of disaccharide glycosides
β Scribed by Grigory M. Lipkind; Alexander S. Shashkov; Suren S. Mamyan; Nikolay K. Kochetkov
- Publisher
- Elsevier Science
- Year
- 1988
- Tongue
- English
- Weight
- 786 KB
- Volume
- 181
- Category
- Article
- ISSN
- 0008-6215
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β¦ Synopsis
Conformations
of (l-2)-, (l&+3)-, and (l-4)linked disaccharide methyl glycosides involving aldohexopyranose residues have been studied on the basis of the inter-unit n.0.e. and theoretical calculations using atom-atom potential functions. The preferred conformations and the n.0.e. values are determined by the absolute configurations of constituent residues, the configuration and position of the glycosidic linkage, and the orientation of the protons at the aglycon carbon associated with the glycosidic linkage and the adjacent carbons.
π SIMILAR VOLUMES
N.O.e. data after pre-irradiation of the anomeric protons and the 3JC,H values associated with the glycosidic linkages for a series of methyl beta-glycosides of trisaccharides that contain 3,4-disubstituted galactose residues have been measured. On the basis of the experimental results and theoretic
On the basis of the n.O.e. data and theoretical calculations, it was found that less than 90% of one conformer was present in aqueous solution for each of a series of trisaccharide methyl beta-glycosides with a 2,3-disubstituted galactose residue.
The configurations of some isoxazolidinium salts have been determined by nuclear Overhauser effect difference spectroscopy (NOEDS). The stereochemical findings give a good explanation of the different reactivities experienced in the five-membered ring-opening process as a function of the steric requ