Amidase activity of phosphonate TSA-built polymer catalysts derived from organic monomers in the amidolysis of amino acid p-nitroanilides

Abstract

Highly crosslinked transition state analogue imprinted macromatric polymer catalysts having imidazole, carboxyl and hydroxyl functional groups in the catalytic sites were synthesized as chymotrypsin mimics using achiral organic monomers 4-vinylimidazole, methacrylic acid, allyl alcohol and phenyl-1-(N-benzyloxycarbonylamino)-2-(phenyl)ethyl phosphonate (transition state analogue of ester and amide hydrolytic reactions) as the template. The catalytic properties of the enzyme mimics were investigated in the amidolytic reactions of l-amino acid p-nitroanilides and correlated to the amidase activities of the catalysts derived from chiral methacryloyl-l-amino acid monomers methacryloyl-l-histidine, methacryloyl-l-aspartic acid and methacryloyl-l-serine. A two-fold enhancement in rate acceleration, substrate specificity, substrate shape-selectivity and stereoselectivity was observed for polymers made up of flexible amino acid monomers compared to the copolymers of organic monomers. The pre-polymerization complex of TSA with methacryloyl-l-amino acid monomers fabricates specific 3D-memory cavity preferentially of l-enantiomer of the TSA in the polymer matrix while the achiral organic monomers designs both L- and D- cavities The effect of crosslink density on the catalytic efficiencies of the polymer catalysts was also investigated. Replacement of allyl alcohol by vinylpyridine afforded catalyst with better enzymatic activity.