Journal of Carbohydrate Chemistry最新文献

Radical glycosylation has gradually become a powerful and effective method to synthesize carbohydrate mimetics as reactions via radical intermediates usually provide excellent functional group compatibility and good anomeric selectivity. Novel glycosyl radical precursors have been identified as glycosyl donors in radical glycosylation to access C-, S- and Se-glycosides. This review aims at summarizing the remarkable advances in radical glycosylation reactions to illuminate potential future research directions. Herein, the most recent literature concerning radical glycosylation is covered with a specific emphasis on radical precursor design along with discussions of consequential mechanisms.

The conversion of D-ribose into its 2,3-O-isopropylidene derivative using ultrasonic irradiation is described. The ultrasound proved to be an excellent alternative as the energy source for the reaction. Different reaction times were investigated, and shorter reaction times and high yield were achieved without the need for purification of the acetonide. The compound was then applied as the starting material in the synthesis of 23 new glycoconjugates of 1,2,3-triazole that are tethered together in different ways. The synthesized compounds were characterized by FTIR, ¹H NMR, ¹³C NMR, and HRMS techniques.

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N-glycans in eukaryotic proteins are commonly attached to asparagine residues via β-N-glycosidic linkages, which are susceptible to glycosidases, such as PNGase. Here we report the preparation of α-N-glycosylated peptides based on the solid-phase peptide synthesis strategy using an α-N-GlcNAc-containing asparagine building block, and a transglycosylation reaction of oligosaccharide oxazoline promoted by endoglycosidases CC^N180H. The resultant glycopeptide, bearing the complex-type α-N-sialyl undecasaccharide, exhibits resistance against PNGase F, which may be of potential use in studying the catabolism of N-glycans and glycoengineering those peptide-based therapeutics.

Glycoclusters with high glycan density accessible through grouping of monosaccharide units in multimeric forms are important due to their high affinity and capability in recognition with protein receptors as a result of multivalent effect. In this report, we have achieved the assembly of glycoclusters in dimeric to tetrameric forms using efficient light initiated free radical mediated thiol-ene click reaction. Bacterium (UTI89) inhibition study by yeast agglutination assay demonstrated that these multivalent glycoclusters showed more efficient inhibition of bacteria when compared to monovalent sugar units.

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Seasonal allergic rhinitis (SAR) is an inflammatory process. In this pilot study, matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS)-based analyses were conducted to investigate the effects of SAR on serum N-glycome in a small dataset (n = 10 for both SAR patients and controls). It was detected that two N-glycan compositions (H6N5E2L1 and H6N5E1L2) were down-regulated in SAR patients. Additionally, five tri-antennary N-glycan traits, including both galactosylated and sialylated (A3GS and A3GL) and non-fucosylated (A3F0GE, A3F0GL, A3F0GS) ones, were decreased. Furthermore, three high-antennary and fucosylated N-glycan traits (A3F, A3EF and A4F) were increased in SAR patients compared to controls.

Two photoreactions for the synthesis of 1- and 2-deoxysugars from thioglycosides were developed. In the presence of Hantzsch ester as an additive, a wide range of 1-deoxysugars were synthesized in moderate to excellent yields under irradiation with UV light without an exogenous photosensitizer. On the other hand, the utilization of 2,4,6-tri-tert-butylpyrimidine (TTBP) as the additive furnished a variety of 2-deoxysugars as the main products from their corresponding thioglycosides. The reported methodology has a broad substrate scope and high functional group tolerance and is scalable to gram-scale reaction.

An alginate (molecular weight [Mw] = 64.8 × 10³, F_M = 0.505) was extracted from brown seaweed Turbinaria ornata, and were separated into three fractions, G-blocks (Mw = 8.0 × 10³, F_M = 0.141), M-blocks (Mw = 4.0 × 10³, F_M = 0.952), and MG-blocks (Mw = 8.0 × 10³, F_M = 0.279). According to biological evaluations in terms of antimicrobial, antioxidant, and cytotoxic activities, the native alginate was not a high bioactive compound, but its two main fractions, G-blocks and M-blocks especially M-blocks, showed higher activities. The native alginate and two main fractions were found to have a linear single-chain conformation in saline solution as observed by small-angle X-ray scattering (SAXS) measurements.

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Herein, we report a novel method for highly efficient and stereoselective construction 1,2-cis-2-amino-2-deoxy-glycosidic linkages using conformation-constrained 2-nitroglycal donors and bifunctional thiourea catalyst. The method enjoys mild reaction conditions, good to excellent stereoselectivity, broad substrate scope, and good to excellent efficiency.

Intramolecular glycosylation with peptides as tethers is attractive for the synthesis of oligosaccharides because conjugation between the amino acids present in the tethers is facile. However, few studies have been published about the effects of the amino acid side chain length and amino acid chirality on the glycosylation process. In this study, we revealed that the chain length of the amino acid can regulate the regioselectivity of the glycosylation process based on our observation that the 1,2-linked products were preferred when tethers were those having aspartic acid residues linked to each other, while 1,3-linked products were preferred for glutamic acid-based tethers. However, the amino acid chirality was found to have no effect on the yield and stereoselectivity of the glycosylation reaction.