Synthesis and conformational analysis of glycomimetic analogs of thiochitobiose

Synthesis of Thiodisaccharides Bearing N-Acetylhexosamine Residues: Challenges, Achievements and Perspectives

Carbohydrate-protein interactions are involved in a myriad of biological processes. Thus, glycomimetics have arisen as one of the most promising synthetic targets to that end. Within the broad variety of glycomimetics, thiodisaccharides have proven to be excellent tools to study these processes, and even more, some of them unveiled interesting biological activities. This review brings together research made on the introduction of N-acetylhexosamine residues into thiodisaccharides to date, passing through classic substitution (as S_N 2, thioglycosylation and ring-opening reactions) and addition (as thiol-ene coupling and Michael-type additions) reactions. Recent and interesting developments regarding addition reactions to vinyl azides, cross-coupling reactions and novel chemoenzymatic methods are also discussed.

Scope of the DMC mediated glycosylation of unprotected sugars with phenols in aqueous solution

Activation of reducing sugars in aqueous solution using DMC and triethylamine in the presence of phenols allows direct stereoselective conversion to the corresponding 1,2-trans aryl glycosides without the need for any protecting groups.

Synthesis, antiasthmatic, and insecticidal/antifungal activities of allosamidins

Allosamidins come from the secondary metabolites of Streptomyces species, and they have the pseudotrisaccharide structures. Allosamidins are chitinase inhibitors that can be used to study the physiological effects of chitinases in a variety of organisms. They have the novel antiasthmatic activity and insecticidal/antifungal activities. Herein, the synthesis and activities of allosamidins were summarized and analyzed.

Thioglycosides Are Efficient Metabolic Decoys of Glycosylation that Reduce Selectin Dependent Leukocyte Adhesion

Metabolic decoys are synthetic analogs of naturally occurring biosynthetic acceptors. These compounds divert cellular biosynthetic pathways by acting as artificial substrates that usurp the activity of natural enzymes. While O-linked glycosides are common, they are only partially effective even at millimolar concentrations. In contrast, we report that N-acetylglucosamine (GlcNAc) incorporated into various thioglycosides robustly truncate cell surface N- and O-linked glycan biosynthesis at 10-100 μM concentrations. The >10-fold greater inhibition is in part due to the resistance of thioglycosides to hydrolysis by intracellular hexosaminidases. The thioglycosides reduce β-galactose incorporation into lactosamine chains, cell surface sialyl Lewis-X expression, and leukocyte rolling on selectin substrates including inflamed endothelial cells under fluid shear. Treatment of granulocytes with thioglycosides prior to infusion into mouse inhibited neutrophil homing to sites of acute inflammation and bone marrow by ∼80%-90%. Overall, thioglycosides represent an easy to synthesize class of efficient metabolic inhibitors or decoys. They reduce N-/O-linked glycan biosynthesis and inflammatory leukocyte accumulation.

Expedient synthesis of an α-S-(1→6)-linked pentaglucosyl thiol

An α-S-(1→6)-linked pentaglucosyl thiol (1) is synthesized via the longest linear sequence of eleven steps from an α-glucosyl thiol (7).

A conformational study of N-acetyl glucosamine derivatives utilizing residual dipolar couplings

The conformational analyses of six non-rigid N-acetyl glucosamine (NAG) derivatives employing residual dipolar couplings (RDCs) and NOEs together with molecular dynamics (MD) simulations are presented. Due to internal dynamics we had to consider different conformer ratios existing in solution. The good quality of the correlation between theoretically and experimentally obtained RDCs show the correctness of the calculated conformers even if the ratios derived from the MD simulations do not exactly meet the experimental data. If possible, the results were compared to former published data and commented.