A Macrocyclic Enzyme Model System. An Electrostatic-Hydrophobic Double-Field Catalysis by a [20]Paracyclophane in the Deacylation of p-Nitrophenyl Hexadecanoate

Abstract

Abstract The catalytic functions of 10-oxo[20]paracyclophanyl-22(23)-methyltrimethylammonium chloride (1) in the hydrolysis and aminolysis reactions of p-nitrophenyl hexadecanoate (PNPP) were investigated in 1%(v/v)methanol–1%(v/v)dioxane-water over the pH 9–10 region at 40.0 °C and μ=0.2 (NaCl) with the initial PNPP concentration of 1.00×10−5 M. The paracyclophane (0.88×10−5 M) accelerated the hydrolysis of PNPP by one order of magnitude at pH 9.7. The presence of either ethanolamine or glycine in the 1-catalyzed deacylation of PNPP resulted in further rate enhancement. The rate enhancement was brought about by the aminolysis reaction of PNPP with the amines as confirmed by the product analysis. The greater reactivity of glycine relative to that of ethanolamine was attributed to the electrostatic interaction between the anionic carboxylate group of glycine and the cationic ammonium group of 1. The novel electrostatic-hydrophobic double-field catalysis was discussed for the glycinolysis reaction.