The synthesis of the locating substitution derivatives of chitosan by click reaction at the 6-position of chitin

A novel method to prepare the macrocyclic compound locating substitution derivatives of chitosan was investigated, by using cyclodextrin as the model of macrocyclic compound. The method combines the advantages of activated 6-OH of chitin and high efficiency of click reaction. Chitin C₆-OH p-toluenesulfonate (CTN-6-OTs) was generated and subsequently transferred to chitin C₆-N₃ via nucleophilic substitution. Afterwards, β-cyclodextrin was immobilized at 6-OH of chitin via click reaction to afford CTN-6-CD. Ultimately, CTS-6-CD was obtained by removing the acetyl group of chitin unit. The structures and properties of these products were characterized by FTIR, TG, and XRD, respectively. It was found that CTN-6-CD synthesized at the optimum conditions has an immobilized loading of 1.6126 × 10-4 mol/g and that of the corresponding CTS-6-CD, generated by removal of the acetyl group, was 1.6891 × 10-4 mol/g.