Disclosed is a compound capable of acting on a ubiquitin-proteosome system, particularly a compound represented by the general formula (I) and having a ubiquitin-binding activity and preferably also having an anti-cancer activity. (I) wherein each symbol is as defined in the description. Also disclosed is a ubiquitin-binding small molecule comprising the compound or a pharmaceutically acceptable salt thereof as an active ingredient particularly having an inhibitory activity on topoisomerase II.
