The invention relates to compounds represented by the general formula (I) and the like. In the formula, Ar1 denotes an aryl or heteroaryl group which may have a substituent R1 denotes a hydrogen atom, or denotes a C1-C6 alkyl, aryl, aralkyl or heteroaryl group which may have a substituent R2 denotes an aralkyl group or a group represented by the formula (a) and R3 denotes a hydrogen atom or a C1-C6 alkyl group. The compounds of the invention have an excellent Wee1 kinase inhibitory effect, and therefore are useful in the field of medicine, especially in the field of treatment of various cancers.
