New derivatives of 3,5-substituted-1,4,2-dioxazoles: synthesis and activity against Entamoeba histolytica

Dioxazole derivatives (1-33) were synthesized in two steps via their corresponding oximes (I-III). All the compounds were characterized using various spectroscopic techniques. A comparative study of in vitro antiamoebic activity of these heterocyclic compounds, viz. 3-o-chloro (1-11), 3-m-chloro (12-22) and 3-p-chloro (23-33) dioxazoles having same substituents at 5-position of dioxazole ring, was performed against HM1:IMSS strain of Entamoeba histolytica. The results showed a regular pattern in the activity and out of 33 compounds assayed 15 compounds showed better antiamoebic activity than metronidazole with IC(50) values in the range 0.41-1.73 microM and 1.80 microM. Dioxazoles having o-chloro, m-chloro, p-chloro, dichloro and pyridine substituents at 5-position were more active than the standard drug metronidazole. The toxicity studies against human kidney epithelial cell line showed that all the compounds were non-toxic. 3,5-Bis-[2-chlorophenyl]-1,4,2-dioxazole (10) was most active and least toxic among all the compounds.