Synthesis of β-1,3-glucan mimics by β-1,3-glucan trisaccharyl monomer polymerization

Abstract

β-1,3-Glucans are important as immunostimulating agents in living organisms. The multivalent binding of β-1,3-glucans to dectin-1, a cell surface receptor, activates immunological defenses. To study artificial immunostimulating agents, glycopolymers carrying β-1,3-glucan trisaccharides as artificial ligands were synthesized. The β-1,3-glucan trisaccharide, defined as an active unit of β-1,3-glucan, was constructed from D-glucose by glycosylation. A norbornene group was introduced as a polymerizable group into the trisaccharide derivative at the aglycone. The prepared endo/exo norbornene stereoisomers of the monomers were separated by silica gel chromatography and identified by NMR spectroscopy and mass spectrometry. The synthesized glycosyl monomers were polymerized and copolymerized with norbornene using 2nd generation Hoveyda-Grubbs catalyst, deprotected, and purified by gel filtration to prepare water-soluble glycopolymers of varied compositions and high molecular weights. These polymers will have the potential for multivalent binding to dectin-1 to activate immune response and facilitate studies to understand the binding mechanisms of β-1,3-glucans with dectin-1.