Quinolone analogues 15: Synthesis and antimalarial activity of 4-phenyl-1-(1-triazolylmethyl-4-quinolon-3-ylcarbonyl)semicarbazide and related compounds

The 1-hydrazinocarbonylmethyl-4-quinolone-3-carboxylate (10) was converted into the 1-(4-amino-1,2,4-triazol-3-ylmethyl)-4-quinolone-3-carboxylic acid (13), whose reaction with arylcarbaldehydes gave the 1-(4-arylmethyleneamino-1, 2,4-triazol-3-ylmethyl)-4-quinolone-3-carboxylic acids (5a, 5b, 5c, 5d, 5e, 5f, 5g). Compound 10 was also transformed into the 1-(4-amino-1,2,4-triazol-3- ylmethyl)-4-quinolone-3-carbohydrazide (15), whose reaction with phenyl isocyanate or phenyl isothiocyanate afforded the 4-phenyl-1-(1-triazolylmethyl- 4-quinolon-3-ylcarbonyl)semicarbazide (6a) or 4-phenyl-1-(1-triazolylmethyl-4- quinolon-3-ylcarbonyl)thiosemicarbazide (6b), respectively. Compounds 6a, 6b showed the in vitro antimalarial activity to chloroquine-resistant Plasmodium falciparum, wherein their IC₅₀ was 3.89 and 3.91 μM, respectively.