Catalysis by imidazolium ion and metal ions in the reaction of a phosphate diester

Abstract

The rates of reaction of catechol cyclic phosphate in water and in acetonitrile-water demonstrate that imidazolium ion and metal ions (Na +, Mg 2+, Zn 2+) cause significant accelerations. These studies provide models for the potential role of cations in catalysis of reactions of phosphate anions by enzymes. In catalysis by Zn 2+, we find that two to three imidazoles are required for coordination to Zn 2+ for most effective catalysis. Enough water must be present to solvate imidazole and coordinate to Zn 2+, indicating that a coordinated H 2O is the nucleophile in Zn 2+ catalysis. Product analysis also supports this conclusion.