Triazole and triazole fused heterocyclic ring systems possess
diverse applications in the fields of medicine, agriculture and
industry. A new series of nalidixic acid derivatives having 1,2,4-
triazole moiety at position 3 were synthesised to achieve enhanced
biological activity and wide spectrum of activity. Nalidixic acid was
first converted into its methyl ester which upon hydrazinolysis
afforded nalidixic acid hydrazide. Condensation of the hydrazide
with CS2/KOH furnished the potassium dithiocarbazate salt, which
cyclized to the 3-[4-amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-
3-yl]-1-ethyl-7-methyl-1H-[1,8]naphthyridin-4-one, (4), on refluxing with hydrazine hydrate. Condensation of the key
intermediate 4 with aryl aldehydes afforded Schiff's bases 5a-f,
while its reaction with alkyl or aralkyl halides gave compounds
6a-e. Furthermore, compounds 5a,e were reacted with benzyl
chloride to afford 7a,b. The chemical structure of the target
compounds was confirmed by IR, 1H-NMR, FAB-MS, EI-MS
spectra and elemental analyses. The title compounds and the
starting Nalidixic acid; were tested for their in-vitro antibacterial
and antifungal activities. Most of the tested compounds showed
comparable antibacterial activity with those of Nalidixic acid and
higher activity than ampicillin. The tested compounds and Nalidixic
acid showed non or moderate antifungal activity in comparison to
clotrimazole as a reference drug.