Controlling anomeric selectivities of glycosylations

The chemical coupling of monosaccharides to complex glycan structures often results in a mixture of anomers, which require time-consuming separation protocols resulting in a loss of material. Routine oligosaccharide synthesis will only be possible when robust stereoselective glycosylations become available. We have introduced chiral auxiliaries for the stereoselective introduction of 1,2-cis-glycosides. This approach significantly expands the scope of polymer-supported oligosaccharide synthesis; the first solid support synthesis of a biologically important branched oligosaccharide having multiple 1,2-cis-glycosidic linkages has been reported. We were the first to show that -sialosides can stereoselectively be installed by altering the electronic properties of the C-5 acetamido function. We have also developed a practical approach for the stereoselective introduction of -arabinofuranosides by locking an arabinosyl donor in a conformation in which nucleophilic attack from the -face is favored. 

Fang T.  Gu Y, Huang W, Boons GJ (2016) Mechanism of glycosylation of anomeric sulfonium ions. J Am Chem Soc 138(9):3002-3011. 

Boltje TJ, Kim JH, Park J, Boons GJ (2010) Chiral-auxiliary-mediated 1,2-cis-glycosylations for the solid-supported synthesis of a biologically important branched a-glucan. Nat Chem 2(7):552-557.