C6-Modifications on chitosan to develop chitosan-based glycopolymers and their lectin-affinities with sigmoidal binding profiles

• Published in: Carbohydrate polymers 2016-02, Vol.137, p.277-286
• Main Authors: Koshiji, Kazuhiro, Nonaka, Yuki, Iwamura, Maho, Dai, Fumiko, Matsuoka, Ryoji, Hasegawa, Teruaki
• Format: Article
• Language: English
• Subjects: Chitosan; Chitosan - chemistry; Click Chemistry; Glycopolymer; Huisgen cycloaddition; Lectins - chemistry; Polymers - chemistry; Regioselective modifications; Stereoisomerism
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2015.10.073

•We synthesized chitosan-based glycopolymers having multiple β-lactosides exclusively at their C6-positions.•Our synthetic routes started from partially deacetylated chitin.•Perfect N-deacetylation/phthaloylation and the subsequent C6-selective bromination/azidation afford 6-azide-6-deoxy-N-phthaloyl-chitosan with excellent structural homogeneity.•The subsequent Cu+-catalyzed Huisgen cycloadditions using alkyne-terminated β-lactoside followed by dephthaloylations gave the chitosan-based glycopolymers.•We assessed lectin-affinities of the resultant chitosan-based glycopolymers to find their unique sigmoidal binding profiles with lectins.•We assume that aggregations of the chitosan-based glycopolymers in aqueous media are responsible for the sigmoidal bindings. Chitosan-based glycopolymers having multiple β-lactosides exclusively at their C6-positions were successfully synthesized from partially deacetylated chitin through perfect N-deacetylation/phthaloylation and C6-selective bromination/azidation to afford 6-azide-6-deoxy-N-phthaloyl-chitosan and the subsequent Cu+-catalyzed Huisgen cycloadditions using alkyne-terminated β-lactoside and/or quaternary ammonium modules followed by dephthaloylations. Lectin-affinities of the resultant chitosan-based glycopolymers were assessed through fluorescence titration assays to show their unique sigmoidal binding profiles with amplified binding constants.