Antibacterial effect of some substituted tricyclic quinazolines and their synthetic precursors.

Eleven substituted tricyclic quinazolines and their synthetic precursors were tested for antibacterial effects. 3-Chloromethylcarbonyl-2-methylquinazolin-4-thione and 5-phenyl-2,3-dihydro-1,2,4-triazolo[4,3-c]quinazolin-3-one had the highest antibacterial effect against Bacillus subtilis, the MIC values being 50 mg/L. Two tested derivatives were more active against Pseudomonas aeruginosa than ampicillin, the IC50 values being 80 and 100 mg/L. The most effective derivatives contained in the structure generally pharmacologically active chromophores--methyl group in position 2 and a chloromethyl configuration on the carbonyl group in position 3.