Synthesis and biological activity of some new imidazolium, pyridinium salts and 6-purine derivatives

ABSTRACT

In a search for new antibacterial agents, the preparation of 5-amino-4-carboxamido-1-[3-chlorophenyl]-3-substituted imidazolium halides [2a-c] was proposed. The synthesis was achieved via two steps, preparation of 5-amino-4-carboxamido-1-[3-chlorophenyl] imidazole [1], followed by quaternization using either alkyl iodides or phenacyl bromide. Treatment of [2] with aqueous alkali yielded 5-carboxamido-4-[3-chlorophenyl]-1-substituted imidazoles [3a-c], in good yield. However, when ethyl bromoacetate was used in this reaction, the corresponding 5H, 6H, 7H, 8H-1-amino-2-[3-chlorophenyl]-6, 8-dioxomidazo [1,5-a] pyrazin-4-ium bromide monohydrate [5] was obtained, which on dehydrobromination yielded the dequaternized and rearranged product [6]. Treatment of [1] with ethyl chloroformate/dimethyl formamide mixture afforded 9H, 9-[3-chlorophenyl] purin-6-1 [8]. Chlorination of the later product yielded the corresponding 6-chloro derivative [10]. Nucleophilic substitution of [10] with either malononitrile or ethyl cyanoacetate afforded the dinitrile and the nitrile ester [12a and b], respectively. The structures of the products were assigned on the basis of satisfactory analytical and spectroscopic data. Also, the biological activities of the prepared compounds were screened against several strains of bacteria