In vitro antiproliferative activities of some pyrimido[4,5e][1,3,4]oxadiazine and [1,2,4]triaz olo[4',3':1,2]pyrimido[4,5 e][1,3,4]oxadiazine derivatives were examined in human malignant cancer cell lines. All synthesized compounds inhibited the growth of malignant cells in a dose dependent manner, but among them 1,5,7trimethyl3phenyl1 H[1,2,4]triazolo[4',3':1,2]pyrimido[4,5e][1,3,4]oxadiazine and [(1,5dimethyl3phenyl1 H[1,2,4]triazolo[4',3':1,2]pyrimido[4,5e][1,3,4]oxadiazin7yl)sulfa nyl]acetonitrile, both with triazole moiety, were found to be more effective than other compounds; they also induced a subG1 peak in the flow cytometry histogram of treated cells compared to controls, indicat ing that apoptotic cell death is involved in toxicity they induce. The results showed that compounds with triazole moiety fused to pyrimido[4,5 e][1,3,4]oxadiazine derivatives are more active than those bearing chlorine or pyrrolidine groups at C7 position.

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