Recent Progress in Polymer-Supported Synthesis of Oligosaccharides and Carbohydrate Libraries

Glycobiology is a rapidly evolving field and tackles many phenomena of biomedical importance. Driven by the need to create more efficient methods for the synthesis of complex oligosaccharides, the last few years have seen a major push toward a general approach amenable to solid-phase synthesis. Different strategies have been explored and a host of glycosylating agents have been investigated. New linker systems, different solid support materials and a variety of protective groups have been evaluated. The development of on-resin analytical techniques such as MAS-NMR have greatly facilitated the development of new methods for solid-phase oligosaccharide synthesis. These methodological advances have been demonstrated by preparation of several complex oligosaccharides. As the coupling yields have been improved to 95% and above, the desired products could be obtained in good yield even after seven glycosylations. In addition to single target structures, carbohydrates have generated rapidly increasing interest with respect to sets of diverse, carbohydrate containing molecules. These efforts are of increasing importance for providing molecular tools to elucidate biological processes. While much has been achieved to date, the difficulties encountered in the solid-phase assembly of oligosaccharides underscore the need for the developments of all facets of carbohydrate chemistry. Given the rapid progress in the past eight years, it is conceivable that the synthesis of simple oligosaccharides may soon be automated. Careful investigations into many parameters will eventually allow the synthetic chemist to enable even non-specialists to create important tools for biochemical, biophysical, and medical applications.