20942-96-5Relevant articles and documents
HYDROGENATION OF D-FRUCTOSE AND D-FRUCTOSE/D-GLUCOSE MIXTURES
Makkee, Michiel,Kieboom, P. G.,Bekkum, Herman van
, p. 225 - 236 (1985)
D-Fructose and D-fructode/D-glucose mixtures have been hydrogenated in water at 60-80 deg and 20-75 atm. of hydrogen with Ni, Cu, Ru, Rh, Pd, Os, Ir, and Pt severally as catalysts.The selectivity for the formation of D-mannitol from D-fructose as well as the selectivity for the hydrogenation of D-fructose in the presence of D-glucose with Cu/silica as the catalyst are substantially higher than those for the other catalysts.With Cu/silica as the catalyst, the hydrogenation of D-fructose is first order with respect to the amount of catalyst and the hydrogen pressure, whereas a shift from first- to zero-order kinetics occurs on going from low (0.8) concentrations of D-fructose.D-Fructose is preferentially hydrogenated via its furanose forms, presumably by attack of a copper hydride-like species at the anomeric carbon atom with inversion of configuration.Preferential adsorption of pyranose with respect to furanose forms occurs, whereas the furanose forms show a much higher reactivity.The mechanism proposed for the copper-catalyzed hydrogenation reaction explains both the enhanced yield of D-mannitol from boric esters of D-fructose and the diastereoselectivity of the hydrogeantion of seven other ketoses.
Identification of alpha-D-glucosylglycerol in sake.
Takenaka,Uchiyama,Imamura
, p. 378 - 385 (2000)
alpha-D-Glucosylglycerol (GG) was found for the first time in sake (Japanese rice wine) in an amount of about 0.5%. GG was also found in miso and mirin which had been brewed by using koji. GG was hydrolyzed into glucose and glycerol in an equimolar ratio with maltase (EC 3.2.1.20, alpha-glucosidase from yeast), but not with emulsin (EC 3.2.1.21, beta-glucosidase from almond). The retention times and mass spectra of trimethylsilyl derivatives by a GC-MS analysis of GG in sake were comparable to those of various GG samples synthesized by glycol cleavage. It was proven that GG in sake consisted of three components, viz., 2-O-alpha-D-glucosyl-glycerol (GG-II), (2R)-1-O-alpha-D-glucosylglycerol (R-GG-I) and (2S)-1-O-alpha-D-glucosylglycerol (S-GG-I). The ratio of the three components in GG was 6:66:28 for sake. It is considered that GG was formed by transglucosylation of the glucosyl groups to glycerol by alpha-glucosidase from koji in the sake mash.
SELECTIVE DEGRADATION OF THE GLYCOSYLURONIC ACID RESIDUES OF COMPLEX CARBOHYDRATES BY LITHIUM DISSOLVED IN ETHYLENEDIAMINE
Lau, James M.,McNeil, Michael,Darvill, Alan G.,Albersheim, Peter
, p. 219 - 244 (2007/10/02)
Lithium metal dissolved in ethylenediamine had been demonstrated to cleave a 3-linked glycosyluronic acid-containing polysaccharide .The present study with model compounds has established that, by lithium treatment, carbohydrates are cleaved at the sites of the glycosyluronic acid residues, regerdless of the point at which other glycosyl residues are attached to the glycosyluronic acid residue.Treatment of carbohydrates with lithium metal dissolved in ethylenediamine also results in cleavage of methyl glycosides, reduction of aldoses, and cleavage of methyl ethers and pyruvic acetals of glycosyl residues.Model compounds were used to demonstrate that oligosaccharides containing only neutral glycosyl residues are largely stable to the reaction conditions (except for the reduction of the glycose residue of each oligosaccharide).Thus, a general procedure for the selective cleavage of underivatized carbohydrates at the glycosyluronic acid residues is described.
