A new class of dihaloquinolones bearing N′-aldehydoglycosylhydrazides, mercapto-1,2,4-triazole, oxadiazoline and α-amino ester precursors:: Synthesis and antimicrobial activity

Reaction of the quinolones 6-8 with hydrazine afforded the hydrazide 9-11 in moderate yields. Condensation of 9 and 11 with CS2/KOH furnished the potassium salts 13 and 14, respectively, which spontaneously afforded the 3-(1,2,4-triazolyl)-quinolones 15 and 16, respectively, on treatment with hydrazine. Reaction of 9 in refluxing CS2/KOH gave the 3-(1,2,4-oxadiazolyl)-quinolone 17. Alternatively, 15 was prepared from 17. The azide derivative 12, obtained from 10, furnished the alpha-amino ester derivative 18, on reaction with the glycine ethyl ester. Coupling of 10 with various sugars gave the N'-aldehydoglycosyl-quinolone-3-yl) carbohydrazides 19a-e. The newly synthesized compounds were screened for their antibacterial activity.