Controlling the stereochemical outcome of O-glycosylation remains one of the key challenges in carbohydrate chemistry. Accessing structurally defined carbohydrates is required for the investigation of carbohydrate-protein interactions and for carbohydrate based drug discovery. There has been an increase in the development and application of catalytic methods for oligosaccharide synthesis in recent years; altering the ligand/catalyst combinations can offer improvements over traditional, stoichiometric methods in terms of yield, anomeric selectivity and atom economy. The development of mild, organocatalytic methods for stereoselective glycosylations is particularly desirable. Organocatalysts can offer advantages over their Lewis acid counterparts, tending to be more tolerant of moisture and air, environmentally benign and therefore more amenable to scale-up. In particular, the synthesis of 2-deoxy glycosides is complicated by the lack of substituents at C-2 able to direct nucleophilic approach. 2-Deoxyhexoses are found as important components of natural products and the anomeric configuration is often instrumental in the biological activity. Efforts within the Galan group have been focused on developing mild, catalytic methods for the stereoselective synthesis of 2-deoxy glycosides. A number of organocatalytic and transition-metal catalyzed methods have been reported via the activation of glycals. These methods are widely applicable to a range of acceptors and glycal donors. Moreover, we have shown that careful choice of either protecting groups or catalytic activation system can control the formation of 2-deoxy or 2,3-deoxy products. Herein, we present our recent developments on the application of gold catalysis in oligosaccharide synthesis.

Stereoselective catalytic synthesis of glycosides

2019 Fall National Meeting

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