2-Deoxy-glycosides, in which the C-2 hydroxyl group is replaced with a hydrogen atom, are important motifs in numerous bioactive natural products and pharmaceutical molecules. Herein, an improved dilauroyl peroxide-mediated radical deiodination reaction by using cyclohexane and ethyl acetate as co-solvent is reported. This is an environmentally benign protocol, which operates smoothly under mild conditions and allows efficient preparation of a series of 2-deoxy-glycosides in up to 98% yields.
Sialic acid binding Ig-like lectins (siglecs) are type I membrane proteins characterized by their sequence similarity and ability to bind sialic acid moieties in glycoproteins and glycolipids. Siglecs can regulate the functions of cells in the innate and adaptive immune systems and promote cell–cell interactions through glycan recognition. Siglec-7, a member of the siglec family, is expressed on NK cells and displays unique ligand binding properties different from the other member of the Siglec family. Siglec-7 prefers α(2,8)-disialyl group and branched α(2,6)-sialyl group containing ligands. In this paper, complexes of Siglec-7 in solution with α(2,8)-disialyl group containing ligand GD3, branched α(2,6)-sialyl group containing ligand LSTb and α(2,6)-sialyl group containing ligand LSTc have been modeled based on the crystal structure of Siglec7-DSLc4[α(2,3)/α(2,6)-disialyl lactotetraosyl 2-(trimethylsilyl)ethyl] complex. Structural analysis of these complexes and calculation of theoretical dissociation constant values helped to conclude that GD3 and LSTb can form better complex with Siglec7 than LSTc in solution and all the ligands, DSLc4, GD3, LSTb, and LSTc can form better complexes in solution than in the crystal structure.
As typical affinities of carbohydrates with their receptors are modest, polymers of carbohydrates (glycopolymers) are exciting tools to probe the multifaceted biological activities of glycans. In this review, the linear glycopolymers and the multivalency effects are first introduced. This is followed by discussions of methods to synthesize these polymers. Subsequently, the interactions of glycopolymers with plant lectins and viral/bacterial carbohydrate binding proteins are discussed. In addition, applications of the glycopolymers in facilitating glycan microarray studies, mimicking cell surface glycans, modulation of the immune system, cryoprotection of protein, and electron-beam lithography are presented to stimulate further development of this fascinating technology.
Glycogenolysis and gluconeogenesis are sensitive to nutritional state and their balances are disrupted in the liver by different pathological states. The regulation of the balance between glucose production and synthesis of glycogen continues to be a matter of investigation because of its implications in diseases and its value for therapeutics. We used the gluconeogenic precursor dihydroxyacetone (DHA) to study glycogen synthesis in isolated rat hepatocytes under gluconeogenic conditions. We used a glycogen phosphorylase (GP) inhibitor, 2-deoxy-2-fluoro-α-D-glucopyranosyl fluoride (F2Glc) to prevented GP from breaking up glycogen into glucose subunits and had a pool of glucose in the medium. Therefore, we evaluated the contribution of DHA as a unique source of carbohydrates on glycogen metabolism. We showed that DHA increased G6P levels that induced both GS activation and its translocation and, thus, an increment of glycogen deposition in a similar way as glucose did.
Stereoselective glycosidic bond formation (termed “glycosidation”) remains a challenge in carbohydrate chemistry. Despite such difficulty, a variety of innovative strategies have been developed. In particular, additive-modulated stereoselective construction of glycosidic linkages has become an emerging trend. In this review, we summarized the recent progress in this area with respect to common glycosyl donors, including thioglycosides, glycosyl imidates, glycosyl acetates, glycosyl hemiacetals, glycosyl phosphates and glycosyl ortho-alkynylbenzoates. Together with their merits/limitations, these achievements shed light on carbohydrate chemistry and enabled the efficient preparation of complex oligosaccharides and glycoconjugates.
An efficient synthetic strategy has been developed for the synthesis of a tetrasaccharide related to the O-specific polysaccharide from Escherichia coli O132 as their 2-aminoethyl glycosides in a very good yield by adopting sequential glycosylation followed by in-situ removal of the p-methoxybenzyl (PMB) group in the same reaction pot. Furthermore, the synthetic route was adapted by carrying out three stereoselective iterative glycosylations followed by in situ removal of the PMB group in one pot. The stereochemical outcomes of all the glycosylation steps were excellent with satisfactory yields.
Synthesis, structural features, and paramagnetic properties of manganese-containing nanocomposites based on polysaccharides arabinogalactan, sulfated arabinogalactan, and κ-carrageenan have been studied. All compounds have been investigated by physical and chemical methods including electron paramagnetic resonance, transmission electron microscopy, infrared spectroscopy, and atomic absorption analysis. It is shown that manganese-containing nanoparticles of 3–6 nm in size were stabilized in the polysaccharide mass by coordination with Mn2+, and the resulting particles have a complex structural organization and are highly EPR active with a spin concentration of about 1020 spin/g. The obtained nanocomposites possess aggregative stability and conserve their properties for a long time.
Oligosaccharides are one of the major bioactive components in Codonopsis pilosula. The present study was to investigate the protective effect of C. pilosula oligosaccharides (CPO) on d-galactose (D-Gal)-induced aging and to illuminate the underlying mechanisms. The results indicated that CPO effectively increased the growth rate as indicated by body weight, attenuated the decline of thymus and liver indexes, and mitigated the pathological liver injury compared with model group rats. CPO could elevate the activities of anti-oxidative enzymes, including CAT, GSH-Px, and SOD, and reduce MDA level in serum, improve SOD and GSH-Px activities in liver, down-regulate the phosphorylation of MAPK cascade signal transduction components – ERK, JNK, and p38, and inhibit the activation of downstream NF-κB signaling. In addition, CPO treatment noticeably prevented the overexpression of inflammatory factors such as TNF-α, IL-6, and IL-1β in serum, inhibited the expression of apoptosis-related proteins caspase-3, caspase-9, and the ratio of Bax/Bcl-2 in liver caused by the inflammatory cascade, reduced cell apoptosis, and improved liver damage. The above studies suggested that CPO could effectively mitigate the D-Gal-induced aging, and the underlying mechanism might be closely related to ROS-induced oxidative stress, inflammation, and apoptosis.
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：