And anomeric configuration

Introduction to 2-D NMR experiments The purpose of the standard 1-D H NMR experiment is to achieve structure-related information about sample protons (i.e., chemical shifts, spin-spin couplings, and integration data) describing the relative number of protons. Applied to anthocyanins, this information may help to identify the aglycone (anthocyanidin), number of monosaccharides present, and anomeric configuration of the monosaccharides. However, for most anthocyanins, the information gained by a standard 1 -D H NMR experiment is insufficient for complete structure elucidation. In recent years, various 2-D NMR experiments have evolved as the most powerful tools for complete structure elucidation of anthocyanins. 

Scheme 2. Mechanistic analysis of reaction pathways for NeuA catalysis that considers the crucial influences of C-3 and anomeric configurations and of chair conformations on the three-point attachment of aldoses as acceptor substrates, Si-face attack leads to regular (4S)-configurated adducts while re-face attack leads to inverted stereochemistry (abbreviations anm = anomerization, inv = ring inversion)...

The sequence and anomeric configuration of the oligosaccharide chain was determined by step-wise hydrolysis with specific glycosidases. The conditions of incubation for hydrolysis are the same as those previously described (12). For the hydroly-... 

A. S. Shashkov, A. I. Usov, Y. A. Knirel, B. A. Dmitriev, and N. K. Kochetkov, Determination of absolute and anomeric configurations of monosaccharides in oligo- and poly-saccharides by glycosylation effects in 13C-NMR spectra, Bioorg. Khim., 7 (1981) 1364-1371. 

B. Mulroney, J. C. Traeger, and B. A. Stone, Determination of both linkage position and anomeric configuration in underivatized glucopyranosyl disaccharides by electrospray mass spectrometry, J. Mass Spectrom., 30 (1995) 1277-1283. 

The mono- (283) and bis-phosphate (284) derivatives of D-threo-2,5-hexodiulose ( 5-keto-D-fructose, 260) were synthesized enzymically and purified by anion-exchange chromatography. The proportions, ring size, and anomeric configuration were determined by 31P and 13C NMR spectroscopy. Compound 283 was found to exist preponderantly (80%) in the /f-pyranose form, with the remainder being present in the 2R.5R-furanose form. Compound 284 assumes two different furanose forms in solution, one ( 80%) being the 2i ,5i -furanose and the other the 2i ,5S -furanose.500... 

In the case of a long and branched sugar chain molecular rotation values in the light of Klync s rules also provided useful information about the absolute and anomeric configurations (9). 

As the quantity of available experimental and theoretical data has increased, there has been a trend towards parametrization of multiple Karplus equations for various structural elements, especially for different coupling pathways, and anomeric configurations. 

NMR spectroscopy Potentially the most informative for glycan structure, linkage position and anomeric configuration analysis. Relatively insensitive [272]... 

Using the condensed system of carbohydrate nomenclature (ref. 2, section 3.7 ref. 4, 2-Carb-38.5), positions of glycosidic linkages and anomeric configurations are expressed in parentheses between the monosaccharide residues that are thus linked. This principle should be adhered to with full names as well as with the abbreviated structures. A short form for repre-... 

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