Showing papers on "Aldose published in 2019"

Investigation of the Mechanism of Conformational Alteration in Ovalbumin as Induced by Glycation with Different Monoses through Conventional Spectrometry and Liquid Chromatography High-Resolution Mass Spectrometry.

Abstract: Glycation between ovalbumin (OVA) and different monoses under mild dry heating at 37 °C was studied. The content of free amino groups decreased dramatically, and the conformational changes based on fluorescence and circular dichroism spectra were evident in glycated OVA. The glycated sites and the average degree of substitution per peptide molecule per site were determined using liquid chromatography high-resolution mass spectrometry. Lysine and arginine were the predominant glyaction sites, in which Lys207 was a relatively reactive site for glycation in all of the conjugates. In general, the extent of glycation of aldose was higher, and its alterations on the steric layouts of protein were more drastic than those of ketose. The configuration of hydroxyl groups at C-4 in sugar epimers might be important for the glycation reactivity and conformational modification in the glycated proteins. These insights would have important implications for the creation of sweetened food products with desirable structures and excellent quality control.

C-Glycosyl Styrene Type Compounds by Pd-Catalyzed Cross-Coupling Reactions of Anhydro-Aldose Tosylhydrazones with Benzyl Bromides

Abstract: C-Glycopyranosyl styrene type compounds are valuable synthetic intermediates whose syntheses are known in rather lengthy procedures. Herein palladium-catalyzed cross-couplings of O-peracylated 2,6-anhydro-aldose tosylhydrazones with benzyl bromides were studied under thermic conditions in the presence of LiOtBu. The reactions gave the corresponding C-glycopyranosyl styrenes in up to 59 % yields. The transformations represent a new, short synthetic sequence to get this type of glycomimetic compounds in 4-5 steps from a free aldose.

Tautomer Structures in Ketose–Aldose Transformation of 1,3-Dihydroxyacetone Studied by Infrared Electroabsorption Spectroscopy

Abstract: The acyclic form of monosaccharides exists in a structural equilibrium, with aldose having the aldehyde group and ketose the ketone group (ketose–aldose equilibrium). A basic catalyst facilitates t...

Catalysis and Stability Effect of Solvent Alcohol on the C6 Aldose Conversion toward Tetrose

Abstract: Conversions of biomass feedstock into various valuable chemicals are of great significance. As a typical route, retro‐aldol condensation of monosaccharide greatly expands the variety of biomass‐derived platform chemicals via a selective C−C splitting. Herein, we describe a solvent‐catalysed strategy to high‐selectively accumulate tetrose (four‐carbon platform chemical) from C6 aldoses via the retro‐aldol/aldol process. We find that alcohol solvents with Lewis acidity facilitate the C−C splitting process of hexose under the catalyst‐free condition. The conversion is the fastest in methanol while it is the slowest in isopropanol. The product distribution is greatly influenced by the alcohols through shifting the equilibrium between tetrose and glycolaldehyde (GA). The addition of catalyst only accelerates the reaction rate, and does not change the product distribution. On the one hand, the acetalization of GA with methanol or ethanol shifts the equilibrium from tetrose toward GA, which results in a low yield of tetrose in methanol or ethanol solvent. On the other hand, tetrose can be well accumulated in isopropanol or n‐butanol, and the yield of tetrose in isopropanol is higher than in n‐butanol because tetrose can be well solvated and stabilized in it. This solvent‐dependent reaction strategy provides a new possibility which contributes to the conversion of biomass feedback into valuable platform chemicals and accumulation of target products by utilizing the solvation effect.

Synthesis of Mono- and Disaccharide 4-[(ω-Sulfanylalkyl)oxy]benzoylhydrazones as Potential Glycoligands for Noble Metal Nanoparticles

Abstract: A procedure has been developed for the synthesis of previously unknown aldose 4-[(ω-sulfanylalkyl) oxy]benzoylhydrazones (where alkyl is hexyl or decyl and aldoses are D-glucose, D-galactose, D-maltose, and D-lactose) that a repromising glycoligands for noble metal nanoparticles. According to the 1H and 13C NMR data, 4-[(ω-sulfanylalkyl)oxy]benzoylhydrazones derived from D-glucose, D-maltose, and D-lactose in crystal and in DMSO-d6 solution have exclusively the cyclic pyranose structure (α- and β-anomers). D-Galactose 4-[(ω-sulfanylalkyl)oxy]benzoylhydrazones in DMSO-d6 solution exist as tautomeric mixtures of cyclic pyranose and open-chain acylhydrazone structures.