Opportunities and challenges in synthetic oligosaccharide and glycoconjugate research

Synthetic oligosaccharides and glycoconjugates are increasingly used as probes for biological research and as lead compounds for drug and vaccine discovery. These endeavours are, however, complicated by a lack of general methods for the routine preparation of these important compounds. Recent developments such as one-pot multi-step protecting-group manipulations, the use of unified monosaccharide building blocks, the introduction of stereoselective glycosylation protocols, and convergent strategies for oligosaccharide assembly, are beginning to address these problems. Furthermore, oligosaccharide synthesis can be facilitated by chemo-enzymatic methods, which employ a range of glycosyl transferases to modify a synthetic oligosaccharide precursor. Glycosynthases, which are mutant glycosidases, that can readily form glycosidic linkages are addressing a lack of a wide range of glycosyltransferases. The power of carbohydrate chemistry is highlighted by an ability to synthesize glycoproteins.