Journal of Carbohydrate Chemistry最新文献

Pseudomonas aeruginosa O11 O-antigen is immunologically active but an exact protective epitope has not yet been identified. Synthesis of O11 O-antigen trisaccharide is of importance for identifying the epitopes. Here, neighboring electron-donating effects are keys to enhance the nucleophilicity of the C3 hydroxyl groups of D- and L-fucosamines, to facilitate the efficient synthesis of the trisaccharide. The disarmed peracetylated glycosyl donor with low glycosylation reactivity and glycosyl trifluoroacetimidate with good stability allowed for the glycosylation under mild conditions. The C6 nucleophilic tosylate substitution of D-galactose with iodine was found to be dependent on the steric effect of the axial C4.

Stereoselective photobromination of 1,6-anhydro-β-D-glucopyranose derivatives occurs at exo-H6. However, photobromination of 4-benzoyl-2,3-isopropylidene-1,6-anhydro-β-D-mannopyranose 6 produced unstable 4-benzoyl-1,6-anhydro-3-keto-β-D-mannopyranose 7. The mechanism of stereoselective oxidation at C-3 could be attributed to the facile radical proton abstraction at C-3, followed by the subsequent bromination of the isopropylidene group, which was subsequently eliminated during the aqueous workup. Thus, the aim of this article is to identify the molecular structure of the unstable compound 7.

In this study, the effects of phosphorylation of Radix Cyathula officinalis polysaccharide (RCPS) on its immunological properties were evaluated using broiler chickens immunized with Newcastle disease vaccine (NDV). The results suggested that phosphorylated RCPS (pRCPS) could enhance antibody titers against NDV vaccination, improve the indexes of thymus, the bursa of fabricius and spleen, and up-regulate IL-2, IL-4, IL-5, IL-6, IL-10, and IFN-γ. Overall, pRCPS could significantly improve cellular and humoral immune responses in broiler chickens immunized with NDV and thus represents a useful immunotherapeutic agent.

A facile method for the synthesis of a series of novel β-acylamino furans stating from renewable monosaccharide was achieved. Glucosamine hydrochloride was selectively N-acylated with acyl chlorides in methanol/triethylamine to yield N-acyl-d-glucosamines, which were subsequently converted into β-acylamino furans through dehydration and cyclization under microwave irradiation.

An expedient approach to C-glycosylated isoquinolines was established based on the coupling of vinyl isonitriles with tetrafuranos-4-yl and pentapyranos-5-yl radicals generated from oxidative decarboxylation of uronic acids derived from monosaccharides and complex oligosaccharides. This approach enjoyed a broad substrate scope and good functional group tolerance, and afforded structurally diverse C-glycosylated isoquinolines in the presence or absence of silver salts. Deprotection of the coupling products was conducted to yield C-glycosylated isoquinolines with multiple hydroxyl groups. These novel architectures would offer opportunities for investigation of their bioactivities.

A facile and practical route for the high-yielding synthesis of various thiourea derivatives of carbohydrates has been accomplished through the coupling of carbohydrate-based azides and amines under Staudinger condition (PPh₃/CS₂). Structures of all the developed compounds have been elucidated using various spectroscopic techniques, including NMR, IR, and MS. Weak interactions within compound 3a have also been discussed through the analysis of its single crystal X-ray data.

The structure and physicochemical properties of rice starch modified with 4-α-glucanotransferase (4αGTase) were compared for different enzyme treatment times (1, 24, and 96 h). Specifically, the gelation properties of native rice starch and 4αGTase-treated rice starch (GS) were analyzed regarding their structural characteristics. The average molecular weight of GS decreased with increasing treatment time, and was 4.73 × 10⁴ g/mol after 96 h of treatment. The chain length distribution was also broadened with the enzyme treatment, as 4αGTase transferred α-glucan from one chain to another. The enzyme treatment also altered the gelation properties and decreased the viscosity of the starch depending on the treatment time, perhaps due to the changes in molecular weight distribution and branched chain length distribution. Moreover, the overall characteristics of GS differed significantly from those of maltodextrin. The physicochemical characteristics of GS with different degrees of 4αGTase treatment suggest that it can be used in the food and pharmaceutical industries.

One strategy for developing glycoside hydrolase (GH) inhibitors is to mimic the conformation of the transition state (TS) along the hydrolysis reaction coordinate. We present a DFT-based model to understand the conformational space of the oxocarbenium cation as a TS in carbohydrate chemistry. Using Bolzano’s theorem, we have demonstrated the existence of a function that divides the puckering coordinate space. These results are compared with the available experimental crystal structures of GH-inhibitor complexes, and a contradictory case (GH92) was computationally studied. Our mathematical model opens a door to design more specific inhibitors and to decipher the catalytic pathways of controversial cases.

Chiral ionic liquids (CILs) are widely used solvents and materials with prominent properties. Carbohydrate-derived imidazolium-based CILs represent a distinctive type of CILs possessing multiple chiral centers from natural chiral pool. Herein, a series of glucopyranoside-substituted imidazolium-based CILs (Glu-imi-CILs) were synthesized and evaluated as ligands for Pd-catalyzed homo-coupling reactions of arylboronic acids in water. The glucopyranoside substituent was instrumental for improving the catalytic activity of the resulting catalysts. Moreover, a Glu-imi-CIL with a free hydroxyl group for additional coordination was found to be the most efficient ligand. A series of symmetric biaryl compounds (13 examples) were synthesized from arylboronic acids by this method in high isolated yields (85−99%).

Fructans are generally divided into two different types: β-D-fructofuranosyl-(2→1)-linked inulin and β-D-fructofuranosyl-(2→6)-linked levan. Previously, Radix Codonopsis was found to be rich in inulin type of fructans with low molecular weight (<5000 Da). In this study, a novel macromolecular fructan with a molecular weight of 1.70 × 10³ KD was isolated from Radix Codonopsis, and its homogeneity was shown to be a single peak by high performance gel permeation chromatography (HPGPC), and its structure was confirmed to contain a new type of linkage, α-D-fructofuranosyl-(2→3)-β-D-fructofuranosyl linkage, by 1D- and 2D-nuclear magnetic resonance (NMR).