Kinetics and molecular modelling studies on the stereoselective hydrolysis of enantiomeric esters by dipeptide catalysts

Abstract

The rate constants of the catalytic hydrolysis of short and long chain N-acylphenylalanine p-nitrophenyl esters by a series of optically active dipeptide catalysts in the presence of surfactant aggregates are presented in order to evaluate their catalytic efficiency and stereoselectivity. Circular dichroism spectra of dipeptide catalysts have also been measured in order to estimate the most probable and stable conformation in micellar solution. On the basis of the kinetic stereoselectivities and CD spectra, molecular modelling studies have been performed in order to determine the preferred conformations and energies of dipeptide catalysts and chiral substrates in the presence of surfactants. An analysis of minimum–energy conformations obtained from the calculation reproduces the sense of the kinetic stereoselectivities.