Strategies in Oligosaccharide Synthesis

Abstract

Carbohydrates play a pivotal role in biological processes as energy sources, markers for cellular recognition and cell signaling, as constituents of nucleotides and as structural components.1–6 Exploration of these processes is dependent on the provision of homogeneous materials to study which are difficult to obtain due to innate heterogeneity found in natural sources. The vast regio- and stereochemical complexity of oligosaccharides makes chemical and enzymatic synthesis tremendously challenging, but with significant effort, well defined targets for use as biological probes can be obtained in this manner. The stereochemical outcome of glycosylation is influenced by a large number of factors and minor changes in the donors and acceptors can cause a larger effect on the glycosylation outcome. Impressive progress has been made in understanding these influences and in developing oligosaccharide synthesis methodology that is more efficient than ever before. Novel methodologies and reagents for oligosaccharide construction via chemical, enzymatic, chemo-enzymatic and automated approaches have been developed however, the construction of oligosaccharide is still a long way from being considered a trivial task. A selection of recent examples displaying a variety of approaches towards oligosaccharide synthesis will be presented here focusing predominantly on O-glycosidic bond formation.