Catalytic Strategies for Stereoselective Carbohydrate Synthesis: Emerging Concepts for Accessing Challenging Glycosides
Charles C. J. Loh
Abstract
The development of innovative catalytic strategies for stereoselective carbohydrate synthesis is rapidly emerging as a theme of general synthetic interest. This research frontier is fuelled by current realization that anomeric and site-selectivity challenges encountered in carbohydrate chemistry are indeed fascinating fundamental synthetic questions, still yet to be satisfactorily addressed. Although specialist carbohydrate chemistry and catalysis developed largely independently over the past three decades, growing recognition of carbohydrates as an excellent platform for catalytic method development is now generating fresh opportunities to advance our understanding of chemical phenomena. Unexpected catalytic mechanisms are often unearthed in such cross-disciplinary endeavours. Moreover, new bond-forming catalytic solutions are in great demand as the definition of biologically relevant glycosidic chemical space has broadened substantially beyond native oligosaccharides to include glycomimetics, rare and non-classical sugars. Distinctly, the last 5 years is marked by an unprecedented flurry of activity in the development of ground-breaking catalytic carbohydrate transformations, leading to robust methods that diverge from classical glycosylation approaches. In this minireview, lately emerging concepts such as noncovalent catalyzed glycosylations, radical catalyzed glycosylations, asymmetric catalytic carbohydrate functionalizations and new glycosylation modalities will be examined.