Furanose

Abstract: The conformations of the aldoses in solution, and the compositions of the equilibrium mixtures formed from aldoses after dissolution in water, have been determined by NMR spectroscopy. Calculations based on non-bonded interactions and on the anomeric effect account for the observed conformations, and allow an approximate prediction of the α:β ratio of pyranoses in equilibrium and of the extent of anhydride formation from sugars in acid solution. In certain circumstances the furanose forms are more stable than the pyranose forms.

Abstract: Isomerization of sugars is used in a variety of industrially relevant processes and in glycolysis. Here, we show that hydrophobic zeolite beta with framework tin or titanium Lewis acid centers isomerizes sugars, e.g., glucose, via reaction pathways that are analogous to those of metalloenzymes. Specifically, experimental and theoretical investigations reveal that glucose partitions into the zeolite in the pyranose form, ring opens to the acyclic form in the presence of the Lewis acid center, isomerizes into the acyclic form of fructose, and finally ring closes to yield the furanose product. The zeolite catalysts provide processing advantages over metalloenzymes such as an ability to work at higher temperatures and in acidic conditions that allow for the isomerization reaction to be coupled with other important conversions.

Abstract: Computational studies have been performed to investigate the origin and magnitude of a biologically important nonbonded interaction: the sulfur-oxygen and selenium-oxygen interaction observed in the thiazole and selenazole nucleosides. Crystallographic studies of the antitumor agents tiazofurin and selenazofurin and their analogues have demonstrated close contacts between the thiazole sulfur or selenazole selenium and the furanose oxygen. Crystallographic evidence that these contacts result from a true intramolecular interaction is reviewed