抄録
N-Alkylcyanopyridinium derivatives which have a cyano group at the 2-, 3-, or 4-position of the pyridine ring were synthesized from the corresponding cyanopyridines and alkyl bromides at 80°C for 72 h under 80 MPa. The bactericidal and bacteriostatic activities of the bromides against Escherichia coli K12 W3110 were strongly affected by the structures of the substituents. Their activities were enhanced in proportion to the alkyl chain length, or the molecular hydrophobicity. The derivatives with the dodecyl group had the same high activities as the derivatives with longer alkyl chains (carbon number = 14 - 18). The introduction of a cyano group enhanced the bactericidal activity, and the derivative with the substituent at the 2-position showed the strongest activity. All of the three dodecylcyanopyridinium bromides had a higher activity in an alkaline medium than in an acidic medium. According to the measurement of the critical vesiculation concentrations of the bromides and the observation with a scanning electron microscope, the cells treated with the bromides leaked turbid materials. The pKa values of the corresponding cyanopyridines did not correlate with their bactericidal activities, but the NMR spectra of the most effective drug, dodecyl-2-cyanopyridinium bromides, implied the increase of the electron density of the ammonium nitrogen atom.
