Orthogonal glycosylation

 
 
 

Chapter 2

Introduction



The advantage of the chemoselective activation strategy in oligosaccharide synthesis lies in efficiency since the glycosyl acceptor has a potential leaving group which also temporarily protects the anomeric center. Therefore, in principle, there is no need for deprotection or protecting-group manipulations prior to coupling reactions. However, the number of available protecting groups and chemoselective glycosylation conditions pose a limitation on the chemoselective sequential glycosylation strategy. [1-4] The minimum requirement for a scheme to overcome the aforementioned limitations would be to combine two chemically distinct glycosylatio
n reactions where one of the leaving groups is activated while the other behaves as a protecting group and vice versa. For this orthogonal strategy, [5]  we selected the phenylthio group and fluoride as the leaving groups, and NIS-AgOTf [6]  and Cp2HfCl2-AgClO4 [7]  as promoters, respectively.


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