The invention relates to a compound of a general formula (I): wherein A 1 and A 2 each mean a nitrogen atom or an optionally-substituted methine group； Ring B means a 5-membered to 7-membered aliphatic ring, or a spiro or bicyclo ring formed from the aliphatic ring and any other 3-membered to 7-membered aliphatic ring； R 1 means a hydrogen atom, or an optionally-substituted C1-C6 alkyl group, or an optionally-substituted aryl, aralkyl or heteroaryl group； R 2 means an optionally-substituted aryl, aralkyl or heteroaryl group； and X means a group of =NH or =O, etc. Based on its excellent Wee1 kinase-inhibitory effect, the compound of the invention has cell growth-inhibitory effect and has an additive/synergistic effect with any other anticancer agent, and is therefore useful in the field of medicine.
