Fluorous-tag assisted synthesis of a glycosaminoglycan mimetic tetrasaccharide as a high-affinity FGF-2 and midkine ligand.

Here, we present the preparation of a sulfated, fully protected tetrasaccharide derivative following the glycosaminoglycan (GAG)-related sequence GlcNAc-ß(1 → 4)-Glc-ß(1 → 3). The tetramer was efficiently assembled via an iterative glycosylation strategy using monosaccharide building blocks. A fluorous tag was attached at position 6 of the reducing end unit enabling the purification of reaction intermediates by simple fluorous solid phase extraction. Fluorescence polarization competition experiments revealed that the synthesized tetrasaccharide strongly interacts with two heparin-binding growth factors, midkine and FGF-2 (IC50 of 270 nM and 2.4 µM, respectively). Our data indicate that this type of oligosaccharide derivatives, displaying sulfates, hydrophobic protecting groups and a fluorinated tail can be considered as interesting GAG mimetics for the regulation of relevant carbohydrate-protein interactions.