Journal of Carbohydrate Chemistry最新文献

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).

To enhance our understanding of the activation and conjugation processes, reported herein is the synthesis of oligosaccharides comprising two sequential repeating units of capsular polysaccharide S. aureus serotype 8 (CP8). As in our previous syntheses of staphylococcal oligosaccharides, the potential propagation positions are blocked with methyl groups. While protein conjugates of carbohydrate antigens based on the structure of the S. aureus capsular serotypes have the potential to contribute to a S. aureus vaccine, despite promising preclinical data, efficacy has not been detected in human populations thus far.

An efficient and practical synthetic strategy, suitable for one-pot synthesis, for novel amide-linked oligosaccharide mimetics from sugar amino acid precursors is described. Twenty substrates, including twelve amide-linked disaccharide mimetics, four amide-linked trisaccharide mimetics and four amide-linked tetrasaccharide mimetics, were synthesized based on this strategy and its optimal conditions. This potentially general method is featured by high yields, gram-scale synthesis, wide substrate scope, and mild reaction conditions.

FeCl₃/C was used as an efficient and convenient promoter for glycosylation through Ferrier-type rearrangement of 3,4,6-tri-O-benzyl-D-glucal, which is a relatively unreactive substrate for this type of reaction. The method was applicable to a wide range of alcohols, especially phenols. A series of 2,3-unsaturated-O-glucosides were prepared efficiently (47–92%) by this method under mild conditions.

D-Glucuronyl C5-epimerase (C5-epi), which converts D-glucuronic acid to L-iduronic acid, is a crucial enzyme in the preparation of bioengineered heparin, which provides an alternative way to produce safer heparins. Herein, we provided an efficient way to measure the activity of cyanogen bromide-immobilized C5-epi based on proton nuclear magnetic resonance (NMR) analysis of perdeutero N-sulfoheparosan C5-epimerization. In this method, reactions catalyzed by C5-epi could be monitored by real-time 1 D NMR according to the peak intensity change of H-5 from IdoA and GlcA residues in the ¹H NMR spectrum, which is nondestructive of sample and also serves the kinetic property evaluation of immobilized C5-epi.