Synthesis, Stability, and Antimicrobial Activity of Diiodobromides of 1H,2H,3H,4H-Pyrido-[4,3-d]Pyrimidinium Derivatives

Iodination of chloroform solutions of the bromides of 1H,2H,3H,4H-pyrido[4,3-d]pyrimidinium with a threefold excess of iodine was performed to synthesize the diiodobromides of the corresponding organic cations. The composition and structure of these compounds were confirmed by UV and H-1 NMR spectroscopic and potentiometric titration methods. Values for the stability constant lg beta (3.05 - 4.68) allowed active iodine concentrations at the bactericidal level to be produced in solutions of 1H,2H,3H,4H-pyrido[4,3-d]pyrimidinium diiodobromides. The minimum inhibitory concentrations (MIC) of 1H,2H,3H,4H-pyrido[4,3-d]pyrimidinium diiodobromides against E. coli were 1.0 +/- 0.25 mg/ml.