An environmentally benign protocol for the synthesis of sugar 1,2-orthoesters in poly(ethylene glycol) dimethyl ether (DMPE)

An environmentally benign procedure has been developed for the synthesis of sugar orthoesters using anhydrous sodium acetate in poly (ethylene glycol)dimethyl ether (DMPE). Various sugar orthoesers were prepared without using volatile organic solvent and quaternary ammonium salt. The sugar orthoesters were obtained in good to excellent yields.

Synthesis & Evaluation of Novel Mannosylated Neoglycolipids for Liposomal Delivery System Applications

Glycosylated NPs, including liposomes, are known to target various receptors involved in cellular carbohydrate transport, of which the mannoside binding receptors are attracting particular attention for their expression on various immune cells, cancers, and cells involved in maintaining central nervous system (CNS) integrity. As part of our interest in NP drug delivery, mannosylated glycoliposomal delivery systems formed from the self-assembly of amphiphilic neoglycolipids were developed, with a C12-alkyl mannopyranoside (ML-C12) being identified as a lead compoundcapable of entrapping, protecting, and improving the delivery of structurally diverse payloads. However, ML-C12 was not without limitations in both the synthesis of the glycolipids, and the physicochemical properties of the resulting glycoliposomes. Herein, the chemical syntheses of a novel series of mannosylated neoglycolipids are reported with the goal of further improving on the previous ML-C12 glyconanoparticles. The current work aimed to use a self-contingent strategy which overcomes previous synthetic limitations to produce neoglycolipids that have one exposed mannose residue, an aromatic scaffold, and two lipid tails with varied alkyl chains. The azido-ending carbohydrates and the carboxylic acid-ending lipid tails were ligated using a new one-pot modified Staudinger chemistry that differed advantageously to previous syntheses. The formation of stable neoglycoliposomes of controllable and ideal sizes (≈100-400 nm) was confirmed via dynamic light scattering (DLS) experiments and transmission electron microscopy (TEM). Beyond chemical advantages, the present study further aimed to establish potential improvements in the biological activity of the neoglycoliposomes. Concanavalin A (Con A) agglutination studies demonstrated efficient and stable cross-linking abilities dependent on the length of the linkers and lipid tails. The efficacy of the glycoliposomes in improving cytosolic uptake was investigated using Nile Red as probe in immune and cancer cell lines. Preliminary ex vivo safety assessments showed that the mannosylated glycoliposomes are hemocompatible, and non-immunogenic. Finally, using a model peptide therapeutic, the relative entrapment capacity and plasma stability of the optimal glycoliposome delivery system was evaluated and compared to the previous neoglycoliposomes. Overall, the new lead glycoliposome showed improved biological activity over ML-C12, in addition to having several chemical benefits including the lack of stereocenters, a longer linker allowing better sugar availability, and ease of synthesis using novel one-pot modified Staudinger chemistry.

Crystal structure of (2R,3S,4S,5R,6S)-2-(acetoxymethyl)-6-((1-acetyl-5-bromo-4-chloro-1H-indol-3-yl)oxy)tetrahydro-2H-pyran-3,4,5-triyl triacetate hemihydrate C24H25BrClNO11

C24H25BrClNO11, monoclinic, C2 (no. 5), a = 28.914(5) Å, b = 7.9349(14) Å, c = 13.062(2) Å, β = 114.867(3)°, V = 2718.9(8) Å3, Z = 4, R gt (F) = 0.0352, wR ref (F 2) = 0.0888, T = 296.15 K.

Controlling the reactions of 1-bromogalactose acetate in methanol using ionic liquids as co-solvents

The reactions of an acetobromogalactose in mixtures of methanol and one of seven different ionic liquids with varying constituent ions were studied. In general, small amounts of ionic liquid in the reaction mixture led to increases in the rate constant compared to methanol, whilst large amounts of ionic liquid led to decreases in the rate constant; this outcome differs significantly from previous reactions proceeding through this mechansim. Temperature dependent kinetic studies indicated that the dominant interaction driving these changes was between the ionic liquid and the transition state of the process. Through considering solvent parameters of ionic liquids, a relationship was found between the changes in the rate constant and both the hydrogen bond accepting ability and polarisability of the solvent, indicating that the interactions affecting reaction outcome are both specific and non-specific in nature; once more, these interactions were different to those observed in previous similar reactions. By changing the amount of ionic liquid in the reaction mixture, additional products not seen in the molecular solvent case were observed, the ratios of which are dependent on the anion of the ionic liquid and the proportion of ionic liquid in the reaction mixture. This demonstrates the importance of considering solvent effects on both the rate and product determining steps and the potential application of such changes is discussed.

O-Mannosylation Affords a Glycopeptide Hydrogel with Inherent Antibacterial Activities against E. coli via Multivalent Interactions between Lectins and Supramolecular Assemblies

Multivalent carbohydrate-lectin interactions play a crucial role in bacterial infection. Biomimicry of multivalent glycosystems represents a major strategy in the repression of bacterial growth. In this study, a new kind of glycopeptide (Naphthyl-Phe-Phe-Ser-Tyr, NMY) scaffold with mannose modification is designed and synthesized, which is able to perform supramolecular self-assembly with the assistance of catalytic enzyme, and present multiple mannose ligands on its self-assembled structure to target mannose-binding proteins. Relying on multivalent carbohydrate-lectin interactions, the glycopeptide hydrogel is able to bind Escherichia coli (E. coli) in high specificity, and result in bacterial adhesion, membrane disruption and subsequent cell death. In vivo wound healing assays reveal that this glycopeptide hydrogel exhibits considerable potentials for promoting wound healing and preventing E. coli infection in a full-thickness skin defect mouse model. Therefore, through a specific mannose-lectin interaction, a biocompatible hydrogel with inherent antibacterial activity against E. coli is achieved without the need to resort to antibiotic or antimicrobial agent treatment, highlighting the potential role of sugar-coated nanomaterials in wound healing and control of bacterial pathogenesis.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2013-2014

This review is the eighth update of the original article published in 1999 on the application of Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2014. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly- saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 37:353-491, 2018.

Tuning of glyconanomaterial shape and size for selective bacterial cell agglutination

Acting as veritable glue, 1D-coated mannose carbon nanotubes efficiently and selectively regulate the agglutination and proliferation of the enterobacteriaEscherichia colitype 1 fimbriae, much better than the mannose coated 3D-micelles.

Effective Amyloid Defibrillation by Polyhydroxyl-Substituted Squaraine Dyes

With an objective to develop β-amyloid destabilizing agents, we have investigated the interactions of a few water-soluble near-infrared (NIR)-absorbing squaraine dyes 1-3 with lysozyme and its amyloid aggregates through photophysical and biophysical techniques. These dyes exhibited strong interactions with lysozyme and β-amyloids in addition to serum albumins as evidenced by the absorption and emission changes. The interactions were found to be spontaneous with association constant values in the range of approximately 10(4)-10(5)  m(-1), as confirmed through half-reciprocal analysis and isothermal calorimetric measurements. Uniquely, such effective interactions of the dyes have led to the complete disassembly of the β-amyloid fibrillar structures to form spherical particles approximately 350 nm in size, as confirmed through photophysical, thioflavin assay, circular dichroism (CD), atomic force microscopy (AFM), TEM, and selected-area electron diffraction (SAED) techniques. These results demonstrate that the squaraine dyes 1-3 under investigation act as effective protein-labelling and destabilizing agents of the protein amyloidogenesis.