Starch derivatives of high degree of functionalization 5. Stepwise carboxymethylation of amylose

Abstract

The stepwise reaction of amylose with monochloroacetic acid carried out heterogeneously in methanol-water medium and sodium hydroxide gives carboxymethylamylose (CMA) with high degree of substitution (DS) up to 2.35. The stepwise increase of total DSCM of CMA decreases gradually with increasing DSCM of the starting polymer. For the determination of the functionalization pattern of the CMA both HPLC and 1H NMR spectroscopy after complete depolymerization were applied. These analyses revealed a statistical content of the different repeating units with regard to 2-, 3-, 6-mono-, 2,3-, 2,6-, 3,6-di-, 2,3,6-tri-, and 2,3,4,6-tetra-O-carboxymethylglucose as well as glucose and a distribution d of the carboxymethyl functions within the repeating units in the order d(O-2) > d(O-6) ≫ d(O-3).