Studies on chemotherapeutics for Mycobacterium tuberculosis. 18. Synthesis and antibacterial activity on Mycobacterium tuberculosis of formyl-8-hydroxyquinoline derivatives

Abstract

The three position isomers of 8-hydroxyquinolinecarboxaldehydes with the formyl group in 2-, 4-, or 5-position, and their derivatives, making a total of 42 compounds, were synthesized. The antibacterial activity of these compounds was tested against human-type tubercle bacilli H37Rv, sensitive strain, and the strain resistant to PAS, INAH, and streptomycin. It was thereby found that the introduction of a formyl group into 2- or 4-position of 8-hydroxyquinoline resulted in a marked decrease in a antibacterial action, while that in the 5-position showed no change from the original compound. The 2-substituted 8-hydroxyquinolinecarboxaldehyde thiosemicarbazones showed increased activity than the original formyl compound, but the 4-and 5-substituted derivatives showed rather a decrease in the activity. The antibacterial activity of 8-hydroxyquinoline-5-carboxaldehyde isonicotinoylhydrazone against the triple-resistant strain was much lower than that against the sensitive strain and this was assumed to be due to the presence of cross resistance with INAH, considering its structure.