A new series of nitrogen-containing heterocycles 4H-1,3,4-oxadiazin-5(6H)-ones derivatives with hydrophobic and long chains were designed and synthesized by direct cyclization reaction of N'-alkylation substituted aroylhydrazines with chloroacetyl chloride. The preliminary assays showed that some of the compounds displayed moderate to good inhibitory activities toward monoamine oxidase (MAO) at the concentration of 10(-5)-10(-3)M, and antitumor activities against human lung cancer A-549 and human prostate cancer PC-3 cell lines at muM level, which might provide new scaffold for anticancer agents. Furthermore, compounds 5i and 5m exhibited significant inhibitory activity on chitin biosynthesis, which might represent a novel class of highly potential inhibitors of chitin synthesis.