The use of thioglycosides and other glycan derivatives with anomeric sulfur linkages is gaining increasing interest, both in synthesis and in various biological contexts. Herein, we demonstrate the occurrence and circumvention of anomerization during 1-S-glycosylation reactions, and present highly efficient and stereocontrolled syntheses of a series of photoprobe-thiosaccharide conjugates. Muta...

A variable temperature-dependent H NMR conformational analysis of JHH coupling constants and NOE enhancements of a series of 8-aza-3-deaza modified guanine nucleosides 2 and 4–8 has been performed in DMSO-d6 and the results compared to those for natural nucleosides dG (1) and G (3). 8-Aza-3-deaza nucleobase modification leads to the stabilization of N-type conformers by ∆∆H of 3.1 kJ mol , whic...

Carbohydrates are an extremely complex group of isomeric molecules that have been difficult to analyze in the gas phase by mass spectrometry because (1) precursor ions and product ions to successive stages of MS(n) are frequently mixtures of isomers, and (2) detailed information about the anomeric configuration and location of specific stereochemical variants of monosaccharides within larger mo...

Partially protected monosaccharides with free anomeric hydroxyl groups are useful in the synthesis of oligosaccharides [ l-31. A number of chemical methods are reported to remove the anomeric acyl group of peracylated carbohydrates [ 4-61, providing a useful route to partially protected saccharides [ 7,8]. Enzymatic reactions have also been used for this purpose [ 9-231. According to previous r...

The possible involvement of mutarotases in glucose metabolism has been studied by examining the anomeric specificities of a number of glycolytic enzymes. Hexokinases from yeast or Ehrlich ascites tumor cells showed only a marginal preference for the cx anomer of glucose. (All configurations, unless otherwise specified, refer to the D configuration of glucose and its derivatives.) The K, values ...

Abstract Based on structures determined by X-ray crystallography, ab initio MP2 calculations type A mesoionic rings give geometries in good agreement with observed values. study of four ring systems, each exocyclic oxygen, nitrogen or carbon groups, shows that the presence and configuration lone pairs significantly influences geometry configurational preference. Using a localised bond model NBO...

The block-localized wave function (BLW) method, which can derive optimal electron-localized state with intramolecular electron delocalization completely deactivated, has been combined with the polarizable continuum model (PCM) to probe the variation of the anomeric effect in solution. Currently both the hyperconjugation and electrostatic models have been called to interpret the anomeric effect ...

A method for the investigation of the influence of protecting groups on the anomeric equilibrium in the sialic acid glycosides has been developed on the basis of the equilibration of O-sialyl hydroxylamines by reversible homolytic scission of the glycosidic bond following the dictates of the Fischer-Ingold persistent radical effect. It is found that a trans-fused 4O,5N-oxazolidinone group stabi...

Ab initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substituent can be seen by comparing the bond length in 2-chloro and 2- boromo substituented phosphinanes. The effect of anomeric effec...