Molecular mechanics (MM3) calculations on phosphonamidate compounds

Abstract

Phosphonamidate compounds are regarded as transition-state analogs for amide hydrolysis reactions and can be used as potent haptens to elicit catalytic antibodies. The MM3 force field has been extended to cover these compounds, based on the structures, conformational energies, and vibrational analyses from MP2/6-31G∗ or B3LYP/6-31G∗ calculations. It was necessary to include a “trans-lone pair effect” in the MM3 force field so that the conformational dependence of the N–P and P–C bond lengths could be reproduced. This effect is similar to the Bohlman effect and the anomeric effect. The MM3-calculated molecular structures agree well with the quantum mechanics results, and the conformational equilibria and vibrational spectra are in fair agreement.