Abstract
In this study, the relationships between dipole moment and medicinal activity of penicillin derivatives are discussed. Four derivatives of penicillin and the stereoisomers of penicillin G are considered for this investigation. Other classes of beta-lactam antibiotics like cephalosporin C and thienamycin are also investigated along with penicillin derivatives for comparison purposes. Four semi-empirical quantum mechanical method (AM1, RM1, PM3 and PM6) and a molecular mechanical method (MMFF) are chosen to calculate dipole moment of these molecules. To our knowledge, this is the first study on dipole moment calculation on penicillin and related molecules. All the compounds, including the isomers, demonstrate a direct correlation between biological activity and dipole moment. This study indicates that dipole moment is a useful parameter for the studies of the biological activity of beta-lactam antibiotics.