Functionalization of amylose with chloroacetate groups and their derivation with α-naphthylacetic acid. Heterogeneous hydrolytic behaviour of the resulting adducts

Abstract

Amylose functionalized with chloroacetate groups was obtained by reaction of amylose with chloroacetyl chloride using pyridine as catalyst and the dimethylformamide/LiCl system as solvent. 13C-NMR spectra at 75.4 MHz of partially modified amylose with chloroacetate groups were studied in order to evaluate the selectivity of the reaction of amylose with chloroacetyl chloride in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C-6 > C-3 > C-2. The coupling of a model bioactive carboxylic acid (a-naphthylacetic acid) to amylose functionalized with chloroacetate groups was carried out by reaction with its potassium salt. High degrees of modification were obtained in all cases. The hydrolysis in the heterogeneous phase of amylose-a-naphthylacetic adducts showed that the release of the bioactive compound is dependent on the sample form and the hydrophilic character of the adduct as well as on the pH value of the medium.