Stereoselective micellar catalysis. Part 5. Deacylation behaviour in the cleavage of enantiomeric esters by optically active catalysts containing the imidazolyl group

Abstract

The rate constants of both acylation and deacylation in the cleavage of the enantiomers of amino acid p-nitrophenyl esters catalysed by optically active catalysts containing the imidazolyl group have been determined in the presence of surfactant micelles at pH 7.30 in 0.02M-phosphate buffer and 25 °C. The kinetic analysis suggests a nucleophilic mechanism which involves acylation followed by deacylation at the imidazolyl group. Micellar catalysis in deacylation as well as acylation is examined in terms of the rate constants and stereoselectivity. The structural effects of catalysts and substrates and the stereoselective reaction mechanism are discussed.