Carbohydrate scaffolds requirements

The simultaneous presence of an azido and an alkyne group on a scaffold is a prerequisite for performing the 1,3-dipolar cycloaddition of such functions in its intramolecular version. In the case of carbohydrates, the sequential introduction of such functions is always feasible but lengthy and laborious synthetic strategies, normally based on protection and deprotection of the hydroxyl sugar groups, are required. For this reason, the intramolecular alkyne-azide of 1,3-dipolar cycloadditions have found more limited application than the intermolecular reaction between these functions. However, this approach is irreplaceable for the oriented preparation of molecular ar-... 

A particularly relevant class of biomolecules comprises the so-called glycoproteins or glycopeptides. As with protein-protein (such as RGD-integrin) interactions, the interactions between carbohydrates and proteins facilitate many important biological processes [11, 12). Monovalent carbohydrate-protein interactions show very weak binding affinities (Kj 10 to 10 M) [7], while multivalent interactions frequently enhance the affinity due to the so-called g/y-coside cluster effects [13,14]. In order to study multivalent carbohydrate-protein interactions, multivalent glycoclusters are required. Polymers, dendrimers, benzene scaffolds, monosaccharides, and others can be used as the base to affix multiple carbohydrate units. Chen et al. [15] chose the cyclic decapeptide cyclo-[GPKAKGPKKK] where the Lys 3, 5, 8, and 10 residues were used for functionalization with propiolic acid to yield the tetravalent alkyne 8a, while... 

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