Synthesis and characterization of chitosan derivatives carrying galactose residues

A series of water‐soluble chitosan derivatives, carrying galactose residues, were synthesized by using an alternative method in which the galactose groups were introduced into amino groups of the derivatives. First, hydroxyethyl chitosan (HECS) and hydroxypropyl chitosan (HPCS) were synthesized under alkaline conditions by using chitosan and propylene or chitosan and ClCH₂CH₂OH as the starting materials, respectively. Then lactobionic acid was added into the systems so as to form galactosylated HECS (Gal‐HECS) and galactosylated HPCS (Gal‐HPCS) with substitution degrees of 53 and 47%, respectively. Lactosaminated HPCS (Lac‐HPCS) and Lactosaminated HECS (Lac‐HECS) were obtained with substitution degrees of 42 and 38%, respectively, by the reductive amination of the mixtures of lactose and HECS or lactose and HPCS with potassium borohydride present in the reaction. The chemical structures of new chitosan derivatives were characterized by FTIR, ¹H NMR, ¹³C NMR, and elemental analysis. Some physical properties were also analyzed by wide angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). The novel chitosan derivatives carrying galactose residues may be used as additives for hepatic targeting delivery. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2161–2167, 2005