This invention relates to an agent for treating or inhibiting recurrence of acute myeloid leukemia and an agent for inhibiting growth of leukemia stem cells comprising a compound represented by formula (I) or a salt thereof: wherein Ar 1 and Ar 2 each represent aryl or heteroaryl； L represents O, S, NH, NHCO, or CONH； X represents CH or N； Y represents C 1-3 -alkylene； Z 1 represents hydrogen, C 1-6 -alkyl, amino-C 1-6 -alkyl, C 1-6 -alkylamino-C 1-6 -alkyl, di(C 1-6 -alkyl)amino-C 1-6 -alkyl, hydroxy-C 1-6 -alkyl, C 1-6 -alkoxy-C 1-6 -alkyl, or carboxy-C 1-6 -alkyl； and Z 2 represents C 1-6 -alkyl, amino-C 1-6 -alkyl, C 1-6 -alkylamino-C 1-6 -alkyl, di(C 1-6 -alkyl)amino-C 1-6 -alkyl, hydroxy-C 1-6 -alkyl, C 1-6 -alkoxy-C 1-6 -alkyl, or carboxy-C 1-6 -alkyl, Z 1 and Z 2 may, together with adjacent nitrogen, form a heterocyclic group containing as a ring member one or more hetero atoms, in addition to the nitrogen adjacent to Z 1 and Z 2 .
