Proton-carbon oligosaccharides

Early conformational studies by HOESY experiments are illustrated by the work of Batta and Kover54 who were able to access oligosaccharide sequencing and conformational distribution around the glycosidic bond in model compounds. These determinations make use of relayed proton-proton-carbon cross-relaxation. 

Conformational analysis of oligosaccharides in solution by NMR spectroscopy is based on the study of chemical shifts, n.O.e. s, and three-bond, proton-carbon coupling constants. Generally, the experimental NMR parameters P. . , (such as n.O.e. s or... 

Until now, the determination of three-dimensional structures of oligosaccharides in solution was based primarily on proton-proton distance information obtained from n.O.e. data. Here, we discuss the application of three-bond proton-carbon coupling constants. 

T.N. Pham, T. Liptaj, K. Bromek, D. Uhrin, Measmement of small one-bond proton-carbon residual dipolar coupling constants in partially oriented C natmal abundance oligosaccharide samples. Analysis of heteronuclear JcH-modulated spectra with the BIRD inversion pulse, J. Magn. Reson. 157 (2002) 200—209. 

Interglycosidic Carbon-Proton Coupling Constants for Oligosaccharides ... 

A very useful source on various NMR techniques and chemical shifts of functionalized carbon atoms that contains tabulated data on monosaccharides is Reference [23]. Specifically correlating functional groups with chemical shifts of protons and the associated carbon is an important tool for elucidating the stmcture of the monosaccharide moiety of many complex oligosaccharides. Since monosaccharides contain one or more chiral centers, absolute configuration must be known in order to predict the conformational shape of the molecules. The outcome of many stereoselective functionalizations of free and partially functionalized monosaccharides depends on conformation. 

The specific correlations of functional groups with the chemical shifts of carbon and associated protons are always important tools for structure elucidation of simple sugars as well as complex oligosaccharides. The conformational behavior [65,66] of a particular disaccharide and oligosaccharide in solution is determined not only by intramolecular interactions but also by potential interactions that exist between the oligosaccharide and its environment. In particular, the nature of the solvent or more generally the environment in which the compound finds itself, can profoundly affect its geometry. Two such important factors, namely the fully solvated state (i. e. the molecule free in solution) and the molecule solvated by a macromolecular receptor (i. e. the molecule bound to the active site of the protein) contribute to the preferred conformation. 

M. Hricovini and I. Tvaroska, Conformational dependence of the one-bond carbon-proton coupling constants in oligosaccharides, Magn. Reson. Chem., 28 (1990) 862-866. 

I. Tvaroska and F. R. Taravel, One-bond carbon-proton coupling constants Angular dependence in a-linked oligosaccharides, Carbohydr. Res., 221 (1991) 83-94. 

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