Glycosides conformational analysis

A. Dondoni, M. Kleban, X. Hu, A. Marra, and H. D. Banks, Glycoside-clustering round calixarenes toward the development of multivalent carbohydrate ligands. Synthesis and conformational analysis of calix[4]arene O- and C-glycoconjugates, J. Org. Chem., 67 (2002) 4722 -733. 

On the other hand, the method examines the rotations of contiguous residues about the glycosidic bonds, for example, C-l-O and O-C-4 in a (1 —> 4)-linked polysaccharide. This method scans the entire conformational space available to a polymer. The analysis can thus proceed either with a regular, helical structure, or a random conformation. The method has been used quite extensively in the conformational analysis of polysaccharides.9 26 The steric... 

The conformational behaviour in solution of a dermatan-derived tetra-saccharide has been explored by means of NMR spectroscopy, especially by NOE-based conformational analysis. RDCs were also measured for the tetrasaccharide in a phage solution and interpreted in combination with restrained MD simulations. The RDC-derived data substantially confirmed the validity of the conformer distribution resulting from the NOE-derived simulations, but allowed an improved definition of the conformational behaviour of the oligosaccharides in solution, which show a moderate flexibility at the central glycosidic linkage. Differences in the shapes of the different species with the IdoA in skew and in chair conformations and in the distribution of the sulphate groups were also highlighted.28... 

Andre, S. Pei, Z. Siebert, H.-C. Ramstrom, O. Cabins, H.-J. Glycosyl-disulfides from dynamic combinatorial libraries as O-glycoside mimetics for plant and endogenous lectins Their reactivities in solid-phase and cell assays and conformational analysis by molecular dynamics simulations. Bioorg. Med. Chem. 2006,14, 6314-6326. 

The presence of at least three different glycosidic linkages, unequivocally demonstrated by the changes in rotation during hydrolysis, requires the assumption of a carbonium-ion mechanism in this polymerization, and a detailed, conformational analysis has been proposed. Some steric control was also noted with change in the solvent.147... 

Hphe molecular mechanism of acid hydrolysis of glycosides is rather well understood today, much confusion being resolved now by the achievements of conformational analysis of carbohydrates (1,2). With regard to the three consecutive steps of reaction (cf. Figure 1)—Le., the formation of a conjugate acid by protonation of either one of the acetalic... 

Cellobiose octaacetate and 1,6-Anhydro-p-cellobiose hexaacetate are compared with respect to their glycosidic conformation [93, 94], For cellobiose octaacetate it was concluded that the conformation in solution is close to that one determined by X-ray crystal structure analysis to cp = 45° and i / = 16° (Fig. 5) whereas the 1,6-anhydro derivative is demonstrated by use of NOEs, relaxation data, and coupling constants 3JC>H to adopt torsional angles of = 25° and ]c = 45° respectively. 

After criticism [142] of the interglycosidic NOEs observed in the previously described study a very precise approach towards the conformational analysis of thea-(l-3) bond was performed by NOE measurements of specifically deuterated compounds [143], The conformation was determined earlier by several interglycosidic NOEs to protons that have their resonances in an area of high spectral overlap. The synthesis of C-deuterated di- and trisaccharides made an unequivocal assignment of the enhanced signals possible. Thus, the enhancements of H2, H3, and H4 of the P-D-mannose upon irradiation of Hl. as well as the enhancement of HS. upon irradiation of HS. man are indicative of the rigid conformation at the glycosidic bond and confirmed the previous study. 

G. Yang, F. Kong, and R. R. Fraser, Synthesis, conformational analysis and glycosidic coupling reactions of highly active substituted 2,7-dioxabicyclo[4.1.0]heptanes 1,2-anhydro-3,4-di-0-benzyl-u-D-xylopyranose, Carbohydr. Res., 258 (1994) 49-58. 

G. Yang and F. Kong, Synthesis, conformational analysis and the glycosidic coupling reaction of substituted 2,7-dioxabicyclo[4.1. OJheptanes 1,2-an hydro-3,4-di-0-bcnzyl-/f I -arabinopyranose, J. Carbohydr. Chem., 13 (1994) 909-921. 

S. J. Angyal and K. Dawes, Conformational analysis in carbohydrate chemistry. Equilibrium between reducing sugars and their glycosidic anhydrides, Aust. J. Chem., 21 (1968) 2747-2760. 

Long-range carbon-carbon coupling constants are a useful tool in the conformational analysis of glycosidic linkages of carbohydrates.52 Figure 14 shows the... 

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