Regioselective Chemoenzymatic Synthesis of Ganglioside Disialyl Tetrasaccharide Epitopes

A novel chemoenzymatic approach for the synthesis of disialyl tetrasaccharide epitopes found as the terminal oligosaccharides of GD1 alpha, GT1a alpha, and GQ1b alpha is described. It relies on chemical manipulation of enzymatically generated trisaccharides as conformationally constrained acceptors for regioselective enzymatic alpha 2-6-sialylation. This strategy provides a new route for easy access to disialyl tetrasaccharide epitopes and their derivatives.