Controlled Synthesis of Amphiphilic Block Copolymers with Pendant N-Acetyl-d-glucosamine Residues by Living Cationic Polymerization and Their Interaction with WGA Lectin

Abstract

Amphiphilic block copolymers of vinyl ethers (VEs) having pendant N-acetyl-d-glucosamine (GlcNAc) residues were synthesized by living cationic polymerization of isobutyl VE (IBVE) and a VE carrying 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-glucose (1). Sequential block copolymerization of 1 and IBVE was conducted by the CF3COOH/EtAlCl2 initiating system in the presence of added base (1,4-dioxane) to yield the precursor block copolymer with a narrow molecular weight distribution (M̄w/M̄n ∼ 1.1) and a regulated segment composition. Deprotection and subsequent N-acetylation of the precursor polymers afforded the GlcNAc-carrying amphiphilic block copolymers with a well-controlled structure. The interaction of the resultant GlcNAc-carrying block copolymer with wheat germ agglutinin (WGA) lectin, which is known to specifically recognize GlcNAc and its oligomers, was investigated. The association constants were evaluated by measuring the changes in fluorescence intensity of WGA observed upon addition of the GlcNAc-carrying polymer to an aqueous solution of WGA. It was clearly demonstrated that the GlcNAc-carrying polymers show a significant increase in binding affinity toward WGA lectin compared to GlcNAc and its oligomers.