Abstract: The invention is to provide a novel anticancer agent or sensitizer for cancer chemotherapy or radiotherapy. A compound of a general formula (I): wherein A means an aryl group or a heteroaryl group, or a group of a formula (a):; R1 means a —(C?O)aOb(C1-C6)alkyl group, a —(C?O)aOb(C2-C6)alkenyl group, a —(C?O)aOb(C3-C6)cycloalkyl group, an aryl group or a heteroaryl group; R2 and R3 each mean a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a —(C?O)aOb(C1-C6)alkyl group or a group of —(C?O)aN(R1e)R2e; R4 means a hydrogen atom or a (C1-C6)alkyl group, and the like have an excellent Wee 1-kinase-inhibitory effect, and are therefore useful in the field of medicine, especially in the field of various cancer treatments.