Synthesis of chitosan C6-substituted cyclodextrin derivatives with tosyl-chitin as the intermediate precursor

A novel method was developed for the preparation of chitosan derivative with a high substitution of cyclodextrins at 6-OH positions. Tosylated chitin at 6-OH positions (6-OTs-Chitin) was prepared and then displaced by a monoamino β-cyclodextrin derivative (Mono-[6-(2-aminoethyl)-amino-6-deoxy]-β- cyclodextrin, CDen) via nucleophilic substitution of the tosyl group to afford the 6-OH substituted cyclodextrin derivatives (Chitin-en-CD). Further removal of acetyl groups on the chitin main chain yielded the C6 substituted cyclodextrin derivatives (CTS-en-CD). The structures of the products were characterized by FTIR and their crystallinity properties were studied by XRD. The thermal stability of the product was studied by TGA. The optimal conditions for nucleophilic substitution of CDen to 6-OTs-Chitin were evaluated and the highest substitution capacity of Chitin-en-CD was found to be 93.97 μmol/g. Substitution capacity of the corresponding CTS-en-CD was 128.68 mol/g, which is much higher than the literature value.