Molecular Orbital Interpretations for Cholinergic Activities of Some Alkyltrialkylammonium Derivatives

Abstract

The electronic structures of alkyltrialkylammonium derivatives were studied by the CNDO/2 method, and cholinomimetic and cholinolytic activities of these compounds were discussed. The remarkable decrease of the positive charge density of N atom and the raising of the lowest vacant (LV) energy level are theoretically observed with the successive ethylation of tetramethylammonium base (TMA). The stepwise lengthening of an onium group of TMA makes the positive charge density of N atom approach decreasingly to a constant value (+0.60), which corresponds to the range of weak agonist. The lengthening, furthermore, causes the gradual raising of the LV energy, of which the value is expected to approach gradually to the range of antagonistic methyltriethylammonium base (-0.83 eV). From these results, we concluded that the larger than +0.60 the positive charge density of N atom and the lower than -0.83 eV the LV energy are, the more potent agonist the compounds become.