Amylase catalyzed synthesis of glycosyl acrylates and their polymerization

Abstract

The enzymatic synthesis of novel (di)saccharide acrylates from starch and 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and 4-hydroxybutyl acrylate (2-HEA, 2-HEMA and 4-HBA) catalyzed by various commercially available amylase preparations is demonstrated. Both liquefaction and saccharification amylases were tested as biocatalysts. Transglycosidation products were only detected in reaction mixtures containing saccharification amylases. The glycoamylase from Aspergillus niger was found to catalyze the synthesis of 2-(α-glucosyloxy)-ethyl acrylate (Glc-α-EA) from starch. The maltogenic amylase from B. stearothermophilus was found to catalyze the synthesis of 2-(α-maltosyloxy)-ethyl acrylate (Glc-Glc-EA). The transglycosidation product was isolated and purified and its structure was confirmed by ¹H-NMR, ¹³C-NMR and ESI mass spectrometry. The selectivity of the enzyme towards the glycosidation position appeared to be extremely high. Only the anomeric hydroxyl group (C₁–OH) of the disaccharide appeared to be glycosidated and the glycosidation products were anomerically pure. Subsequently, the enzymatically synthesized maltosyl acrylate was successfully polymerized by aqueous free radical polymerization to yield a novel acrylic polymer with pendant maltosyl units.