One pot synthesis of thio-glycosides via aziridine opening reactions.

A one-pot aziridine opening reaction by glycosyl thiols generated in situ from the corresponding anomeric thio-acetates affords thio-glycosides with a pseudo-disaccharide structure and an N-linked tether. The scope of the one-pot aziridine opening reaction was explored on a series of mono- and disaccharides, creating a class of pseudo-glycosidic compounds with potential for further functionalization. Unexpected anomerization of glycosyl thiols was observed under the reaction conditions and the influence of temperature, base and solvent on the isomerization was investigated. Single isomers were obtained in good to acceptable yields for mannose, rhamnose and sialic acid derivatives. The class of thio-glycomimetics synthesized can potentially be recognized by various lectins, while presenting hydrolytic and enzymatic stability. The nitrogen functionality incorporated in the glycomimetics can be exploited for further functionalization, including tethering to linkers, scaffolds or peptide residues.

Design and synthesis of glycomimetics: Recent advances.

In the past few decades, our understanding of glycan information-encoding power has notably increased, thus leading to a significant growth also in the design and synthesis of glycomimetic probes. Combining data from multiple analytical sources, such as crystallography, nuclear magnetic resonance spectroscopy, and other biophysical methods (eg, surface plasmon resonance and carbohydrate microarrays) has allowed to shed light on the key interaction events between carbohydrates and their protein-targets. However, the low metabolic stability of carbohydrates and their high hydrophilicity, which translates in low bioavailability, undermine their development as drugs. In this framework, the design of chemically modified analogues (called carbohydrate mimics or glycomimetics) appears as a valid alternative for the development of therapeutic agents. Glycomimetics, as structural and functional mimics of carbohydrates, can replace the native ligands in the interaction with target proteins, but are designed to show enhanced enzymatic stability and bioavailability and, possibly, an improved affinity and selectivity toward the target. In the present account, we specifically focus on the most recent advances in the design and synthesis of glycomimetics. In particular, we highlight the efforts of the scientific community in the development of straightforward synthetic procedures for the preparation of sugar mimics and in their preliminary biological evaluation.

Facile access to pseudo-thio-1,2-dimannoside, a new glycomimetic DC-SIGN antagonist.

The synthesis and conformational analysis of pseudo-thio-1,2-dimannoside are described. This molecule mimics mannobioside (Manα(1,2)Man) and is an analog of pseudo-1,2-dimannoside, with expected increased stability to enzymatic hydrolysis. A short and efficient synthesis was developed based on an epoxide ring-opening reaction by a mannosyl thiolate, generated in situ from the corresponding thioacetate. NMR-NOESY studies supported by MM3∗ calculations showed that the pseudo-thio-1,2-dimannoside shares the conformational behavior of the pseudo-1,2-dimannoside and is a structural mimic of the natural disaccharide. Its affinity for DC-SIGN was measured by SPR and found to be comparable to the corresponding O-linked analog, offering good opportunities for further developments.