Provided is a compound represented by general formula (1) or a pharmaceutically-acceptable salt thereof. [In formula (1), R1 and R2 may be the same or different from each other, and each represents a hydrogen atom, a halogen atom, a hydroxy group, a carboxy group, a cyano group, or an optionally-substituted C1-6 alkyl group or the like； R3 represents a hydrogen atom； R4 represents an optionally-substituted 4- to 10-membered monocyclic heterocyclic group containing 1-4 heteroatoms selected from an oxygen atom, a nitrogen atom, and a sulfur atom； X represents a group represented by -CH2-, -CH2-CH2-, -CH2-CH2-CH2-, or -CH2-O-CH2-； and Z represents a hydrogen atom or a hydroxy group.]
