The present invention relates to a compound of formula (I) or a pharmaceutically acceptable salt thereof, which is useful as a novel antitumor drug whose target is CSC that is thought to be involved in continuous growth of malignant tumor, cancer metastasis, recurrent cancer, and antitumor-drug resistance:wherein R1A, R1B, R1C, and R1Dare hydrogen atom, etc., R2Aand R2Bare hydrogen atom, etc., R3A, R3B, R3C, and R3Dare hydrogen atom, etc., L is bond, etc., V is C1-6alkylene, and Q is optionally-substituted imidazole.本發明係關於一種以提示與惡性腫瘤之持續性增殖、癌之轉移、復發及對抗腫瘤劑之抗藥性重要關聯之CSC作為標的之作為新穎抗腫瘤劑有用之式(I)所表示之化合物或其製藥學上所容許之鹽。[式中，R1A、R1B、R1C及R1D為氫原子等，R2A及R2B為氫原子等，R3A、R3B、R3C及R3D為氫原子等，L表示鍵等，V表示C1-6伸烷基，Q表示可經取代之咪唑]
