Preparation and characterization of N-[2-(glycosyloxy)-ethyl]chitosan derivatives☆

Abstract Allyl glycosides of 8 simple sugars have been prepared and characterized, including 1 H- and 13 C-n.m.r. assignments. Formylmethyl glycosides, obtained by reductive ozonolysis of the allyl glycosides, have been reductively N -alkylated to chitosan with typical yields of 80%. The glycosides of α- and β- d -glucopyranose, α- and β- d -galactopyranose, 2-acetamido-2-deoxy-α- and β- d -glucopyranose, β- d -glucuronic acid, and β-lactose have been incorporated by this method. The degree of substitution (d.s.) of the products was controlled by varying the molar ratio of glycoside to free amine groups of chitosan by between 0.5 and 3.0. Derivatives of degree of substitution >0.3 were typically water soluble, and compounds of higher d.s. generally gave less-viscous aqueous solutions. Assignment of 13 C-n.m.r. chemical shifts verified the structure of these derivatives. The linewidths of the branch resonances (5–100 Hz) provided qualitative information about the relationship between d.s. and branch mobility. The resonances of high-d.s. products were narrower and more intense than analogous low-d.s. derivatives. The chitosan resonances of the backbone were generally broader (50–200 Hz) and less intense, and as a result were difficult to assign fully.