Synthesis of a conjugable hexasaccharide corresponding to the capsular polysaccharide of Campylobacter jejuni strain BH0142

The first assembly of a conjugation-ready hexasaccharide from the capsular glycan of C.jejuni.strain BH0142 has been accomplished.The synthesis features the efficient preparation of 6-deoxy-D-idoheptopyranosyl fluoride donors proceeding from allylα-D-C-glucopyranoside by a C1-to-C5 switch strategy with radical dehydroxymethylative fluorination as a key step,stereocontrolled construction of 1,2-trans-α-D-ido-heptopyranosidic bonds and of 1,2-cis-α-D-galactopyranosidic linkages.The obtained target oligosaccharide sets a solid foundation for making structurally-defined multivalent glycoconjugate vaccine candidates against C.jejuni.infections.

Assembly of a Library of Trisaccharides as Mimics of Sialyl Lewis Xvia Random Combination Strategy

A small library containing six positional isomers of fucosyl on the modified lactoside backbone as mimics of the Sialyl Lewis X was synthesized via random combinatorial glycosylation, which was charactered by ESI-MS and HPLC.

Donor Preactivation-Based Glycosylation:An Efficient Strategy for Glycan Synthesis

Carbohydrates have gained a lot of appreciation in the past few decades due to their important roles in numerous biological events.Acquiring a structurally well-defined carbohydrate compound is essential for the understanding of its functions.Although some innovative methods have been developed for the synthesis of complex oligosaccharides,glycan synthesis is in general still a time-consuming and difficult work.Herein,we will introduce the preactivation-based glycosylation strategy,which is an efficient protocol independent of the reactivity of glycosyl donor.This review will focus on summarizing the versatile applications of preactivation strategy in stereoselective glycosylation and one-pot assembly of biologically important oligosaccharides and even polysaccharides。

Capture-Release Strategy Facilitates Rapid Enzymatic Assembly of Oligosaccharides

A convenient and highly efficient strategy was developed for the simplification of enzymatic synthesis and purification of oligosaccharides.Glycosyl acceptors terminated with a thiol tag were extended by enzymatic modular assembly(EMA)in the aqueous phase,and the desired products were captured during solid-phase workup(SPW)using commercially available thiopropyl Sepharose 6B resin through a reversible disulfide linkage.Finally,the products were released from solid-phase resin in the presence of dithio-threitol(DTT)as reducing agent and the resin could be recovered and reused.This strategy overcomes the uncertain influence of polymer-or ionic-supports commonly used in enzymatic glycosylation,and showed perfect compatibility with all 10 enzyme modules for the rapid assembly of a series of complex oligosaccharides.

Appraisal of an oligomerization behavior of unprotected carbohydrates induced by phosphorus reagent

In this article, a novel oligomerization behavior of unprotected monosaccharides was discovered in a one-pot reaction induced by phosphorus reagent at room temperature. The inherent characteristics of the oligomerization reaction were dissected in detail by mass spectrometry based method combined with NMR technology. It was found that the main glycosidic bonding pattern is (1→6) linkage with 66% regioselectivity for each step. The ratio of α-(1→6) and β-(1→6) glycosidic bonds formed is around 1:1. The reactivity of 1-OH group from aldoses and the driving force from penta-coordinated phosphorus intermediates are the two critical factors for the oligomerization, according to the monitoring experiments by ESI-MS and NMR. Besides, the oligomerization reaction has good compatibility for various aldoses and could expand to O-glycosylated modification of peptides in vitro. The above results will provide a novel enlightenment to develop more convenient and higher-efficient methods for the synthesis of oligosaccharide library.