Ionic liquids in oligosaccharide synthesis: towards mucin-type glycan probes

Recent applications of ionic liquid-based tags in glycoscience

The functionalization of glycosides with ionic compounds such as ionic liquids provides enhanced polarity for the labelled glycans thanks to the presence of a permanent positive charge. The chemical derivatisation of glycans with ionic liquids constitutes an emerging strategy to boost the detection sensitivity in MS applications. This allows the straightforward monitoring and detection of the presence of labelled glycans in complex matrices and in those cases where very limited amounts of material were available such as in biological samples and chemoenzymatic reactions. The use of ionic liquid based derivatisation agents can be further exploited for the labelling of live cells via metabolic oligosaccharide engineering for the detection of cancer biomarkers and for the tuning of live cells-surface properties with implications in cancer prognosis and progression. In this mini-review we summarise the latest development of the ionic liquid based derivatisation agents in glycoscience focussing on their use for sensitive MS applications.

Synthesis and Glycosidation of Anomeric Halides: Evolution from Early Studies to Modern Methods of the 21st Century

Advances in synthetic carbohydrate chemistry have dramatically improved access to common glycans. However, many novel methods still fail to adequately address challenges associated with chemical glycosylation and glycan synthesis. Since a challenge of glycosylation has remained, scientists have been frequently returning to the traditional glycosyl donors. This review is dedicated to glycosyl halides that have played crucial roles in shaping the field of glycosciences and continue to pave the way toward our understanding of chemical glycosylation.

Fast Identification and Quantification of Uropathogenic E. coli through Cluster Analysis

Rapid diagnostic tools to detect, identify, and enumerate bacteria are key to maintaining effective antibiotic stewardship and avoiding the unnecessary prescription of broad-spectrum agents. In this study, a 15 min agglutination assay is developed that relies on the use of mannose-functionalized polymeric microspheres in combination with cluster analysis. This allows for the identification and enumeration of laboratory (BW25113), clinical isolate (NCTC 12241), and uropathogenic Escherichia coli strains (NCTC 9001, NCTC 13958, J96, and CFT073) at clinically relevant concentrations in tryptic soy broth (10³-10⁸ CFU/mL) and in urine (10⁵-10⁸ CFU/mL). This fast, simple, and efficient assay offers a step forward toward efficient point-of-care diagnostics for common urinary tract infections.

Automated Chemical Oligosaccharide Synthesis: Novel Approach to Traditional Challenges

Advances in carbohydrate chemistry have certainly made common oligosaccharides much more accessible. However, many current methods still rely heavily upon specialized knowledge of carbohydrate chemistry. The application of automated technologies to chemical and life science applications such as genomics and proteomics represents a vibrant field. These automated technologies also present opportunities for their application to organic synthesis, including that of the synthesis of oligosaccharides. However, application of automated methods to the synthesis of carbohydrates is an underdeveloped area as compared to other classes of biomolecules. The overarching goal of this review article is to present the advances that have been made at the interface of carbohydrate chemistry and automated technology.

Methods for 2-Deoxyglycoside Synthesis

Deoxy-sugars often play a critical role in modulating the potency of many bioactive natural products. Accordingly, there has been sustained interest in methods for their synthesis over the past several decades. The focus of much of this work has been on developing new glycosylation reactions that permit the mild and selective construction of deoxyglycosides. This Review covers classical approaches to deoxyglycoside synthesis, as well as more recently developed chemistry that aims to control the selectivity of the reaction through rational design of the promoter. Where relevant, the application of this chemistry to natural product synthesis will also be described.

Stereoselective Glycosylation of 2-Nitrogalactals Catalyzed by a Bifunctional Organocatalyst

The use of a bifunctional cinchona/thiourea organocatalyst for the direct and α-stereoselective glycosylation of 2-nitrogalactals is demonstrated for the first time. The conditions are mild, practical, and applicable to a wide range of glycoside acceptors with products being isolated in good to excellent yields. The method is exemplified in the synthesis of mucin type Core 6 and 7 glycopeptides.

Stereocontrolled 1,2-cis glycosylation as the driving force of progress in synthetic carbohydrate chemistry

Recent developments in stereoselective 1,2-cis glycosylation that have emerged during the past decade are surveyed herein.

Recent developments in stereoselective 1,2-cis glycosylation that have emerged during the past decade are surveyed herein. For detailed coverage of the previous achievements in the field the reader is referred to our earlier reviews: A. V. Demchenko, Curr. Org. Chem. , 2003, 7 , 35–79 and Synlett , 2003, 1225–1240.

Synthesis of mucin-type O-glycan probes as aminopropyl glycosides

The chemical synthesis of a series of mucin-type oligosaccharide fragments 1-7 containing an α-linked aminopropyl spacer ready for glycoarray attachment is reported. A highly convergent and stereoselective strategy that employs two different orthogonal protected galactosamine building blocks was used to access all of the targets. A tandem deprotection sequence, that did not require chromatography-based purification between steps, was employed to globally unmask all protecting groups and all final targets were isolated in good to excellent yields.

HPLC-assisted automated oligosaccharide synthesis

A standard HPLC was adapted to polymer supported oligosaccharide synthesis. Solution-based reagents are delivered using a software-controlled solvent delivery system. The reaction progress and completion can be monitored in real time using a standard UV detector. All steps of oligosaccharide assembly including loading, glycosylation, deprotection, and cleavage can be performed using this setup.

Expeditious oligosaccharide synthesis via selective, semi-orthogonal, and orthogonal activation

Traditional strategies for oligosaccharide synthesis often require extensive protecting and/or leaving group manipulations between each glycosylation step, thereby increasing the total number of synthetic steps while decreasing the efficiency of the synthesis. In contrast, expeditious strategies allow for the rapid chemical synthesis of complex carbohydrates by minimizing extraneous chemical manipulations. Oligosaccharide synthesis by selective activation of one leaving group over another is one such expeditious strategy. Herein, the significant improvements that have recently emerged in the area of the selective activation are discussed. The development of orthogonal strategy further expands the scope of the selective activation methodology. Surveyed in this article, are representative examples wherein these excellent innovations have been applied to the synthesis of various oligosaccharide sequences.

Structural glycobiology and human health

The glycans (carbohydrates) form a diverse group of biomolecules which play active parts in most physiological processes. The field of structural glycobiology concerns the structures of the glycans themselves, the proteins which interact with them and the nature of the interactions between the two. The resulting information is important for our understanding of human health and disease, and for development of new therapeutic strategies. A series of articles is introduced based on the topics covered at the Structural Glycobiology and Human Health Biochemical Society Focused Meeting. Their subjects range from in-depth determinations of three-dimensional protein structure to broad screening techniques for glycan-protein interactions relevant to disease processes, including bacterial, parasitic and viral infections, inflammatory processes, cancer and diabetes.