A cationic gold(I)-catalyzed O-glycosylation method involving the use of glycosyl S-3-butynyl thiocarbonate donors has been developed. It was found that glycosyl S-3-butynyl thiocarbonates are orthogonal to regular phenyl thioglycoside donors. The utilization of this method was demonstrated in the synthesis of a trisaccharide.
A new and sustainable preparation of zwitterionic monoamides of galactaric acid is reported. The protocol consists of an efficient conversion of aldaric acid into the corresponding lactone and its further reaction in the presence of diamines, leading to the formation of the corresponding zwitterionic monoamides in high yields and selectivity. The zwitterions have been used as monomers to obtain the corresponding polyhydroxyamides. The overall protocol has shown a high atom economy, and all the carbon atoms present in the reagents are preserved.
The ratio of counter-regulatory hormones to insulin is increased in diabetes. This causes a change in the activities of the enzymes involved in glycogen metabolism. Thus, it is expected that the structure of glycogen will be changed reversibly in diabetes mellitus. The current research was done to study whether the fractions of glycogen have been changed in streptozotocin (STZ)-induced diabetes in rats. To this end, one group of 10 male rats received a single injection with STZ and were compared with the control group. Liver glycogen fractions were analyzed for the content of carbohydrates, protein, and organic phosphate. Hyperglycemia and clinical signs of diabetes appeared after two days of STZ- injection and continued up to two weeks. In diabetic rats relative to controls, total glycogen decreased by about 39% (24.4 ± 3.0 mg/g wet weight of liver vs. 39.7 ± 2.2, p = 0.001), and the change happened entirely in acid-soluble glycogen (ASG) fraction (19.1 ± 1.7 vs. 33.4 ± 2.2, p = 0.001), while acid-insoluble glycogen (AIG) increased slightly but not significantly (5.5 ± 1.1, vs. 4.5 ± 0.8, p = 0.5). Diabetes was also associated with the change in the content of glycogen protein and the ratio of ASG to AIG. The content of organic phosphate was 181.4 ± 26.3 and 39.2 ± 7.9 µg/g wet weight of liver for ASG and AIG fractions in control rats and had no significant change in diabetes. In conclusion, diabetes is accompanied by the reduction in liver glycogen carbohydrate and protein of total and soluble fraction but the content of organic phosphate has not been affected.
Thiosugars are not only playing important roles in saccharide synthesis but also occur widely in pharmaceutical agents, natural products and S-glycopeptides/proteins, and possess critical biological activities. Many methods have been developed for the syntheses of thiosugars, but most of them adopted saturated-glycosyl donors to give 1-thiosugars only. With the development of olefin-chemistry and transition metal catalysis, numerous protocols of thiosugar synthesis were developed with 1,2-unsaturated-glycosyl donors (glycals) giving different stereoselectivity and regioselectivity. In this review, we have summarized the synthetic methods of thiosugars using glycal donors based on promoters/catalysts, including main-group, transition metal, rare-earth and solid-supported catalysts.
The excellent biocompatibility and unique inclusion capability as well as powerful functionalization capacity of cyclodextrins and their derivatives make them especially attractive for engineering novel functional materials for many applications. There has been increasing interest recently to fabricate supramolecular systems based on cyclodextrin materials. This review focuses on state-of-the-art and recent advances in the construction of cyclodextrin-based assemblies and their practical applications in many fields like gene therapy, chemotherapy, antimicrobial drug delivery, metal extraction, food industry, etc. Supramolecular self-assembly materials based on cyclodextrins are also discussed in this review. The fabrication technologies of supramolecular systems including nanoplatforms and hydrogels as well as their applications in nanomedicine and pharmaceutical sciences are highlighted. In the end, the future directions of this field are discussed.
An efficient approach for the facile synthesis of a potent vaccine adjuvant RC-529 is described. The synthetic strategy relies on the flexible use of orthogonal protecting groups, which makes it possible to accomplish selective phosphorylation, glycosylation and acylation, respectively. In addition, the use of readily cleaved 2-naphthylmethyl (Nap) ether and allyl esters as permanent protecting groups greatly facilitates the final global deprotection steps to obtain pure RC-529. This work will contribute to the synthesis of lipid A and its derivatives.
An alkali-extracted polysaccharide (HY-B) was isolated and purified from Dioscorea opposita Thunb. (Huai Yam). Its chemical structure was analyzed with FT-IR, GC-MS and 1 D, 2 D-NMR spectrometry. It was proved that HY-B is mainly composed of α-1,4-linked glucose, which is similar to starch, but the starch-iodine color test proved that it was not starch. The chain conformation of HY-B was analyzed by SEC-MALLS-RI and TEM, indicated that HY-B exists in a random coil conformation. Its molecular weight is 18.7 kDa, and the molecular size is about 100 nm. MTT assays indicated that HY-B was nontoxic to RAW 264.7 cells in vitro. The results of anti-inflammatory studies showed that HY-B could inhibit the production of NO and TNF-α in RAW 264.7 macrophage stimulated by lipopolysaccharides (LPSs). This work provided the important information about the anti-inflammatory active component of Huai Yam and its potential applications in the food and health industries.
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.
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