Abstract: The purpose of the invention is to develop, as drug-candidate compounds, a group of novel compounds having the activity of inhibiting functions of Pin1. The invention provides: a compound represented by formula (I) or a salt thereof; and a Pin1 inhibitor, a pharmaceutical composition, a therapeutic or prophylactic agent for inflammatory diseases, a therapeutic or prophylactic agent for cancer, and a therapeutic or prophylactic agent for adiposity that use said compound/salt.