Structure-activity correlations for a series of antiallergy agents. 2. Geometric and electronic characterization of some oxamic and dioxamic acids.
Hartree-Fock self-consistent field calculations using the ab initio molecular fragment technique have been performed on some phenyloxamic and m-phenylenedioxamic acids, which exhibit markedly different activities in the rat passive cutaneous anaphylaxis (PCA) assay. Attention is focused upon structural features that are most likely to affect the drug-receptor interactions, such as the preferred molecular geometry, the electronic charge distribution, and the nature of the higher occupied (HOMO) and lower unoccupied (LUMO) molecular orbitals. Judging from the regions of high density in HOMOs and LUMOs, the benzene ring would preferably act as an electron acceptor, while the oxamic acid moiety would serve best as an electron donor. Factors affecting the relative PCA activities of oxamic and dioxamic acids are discussed.