Compound, organic cation transporter 3 detection agent, and organic cation transporter 3 activity inhibitor

A compound represented by the following formula (A), a pharmaceutically acceptable salt thereof, or a pharmaceutically acceptable solvate thereof,

• R1-R2-R3-R4 (A)
• wherein,
• R1 represents a group represented by (H2N)2C═N—
• —R2— represents a group represented by
• —R3— represents
• a group represented by —R36-R37-R38—, wherein
• —R36— represents a methylene group,
• —R37— represents —O— or —S—, and
• —R38— represents an ethylene group, and
• —R4 represents
• a group represented by —R41-R42,
• a group represented by —C(NH2)═NR43,
• a group represented by —NHC(NH(R46))═R44R45, or
• a group represented by —NHR48, wherein
• —R41— represents a group represented by
• —R42— represents a C7-10 aralkyl group,
• R43 represents —SO2—R431, wherein
• R431 represents an amino group or a trifluoromethyl group,
• R44 represents a nitrogen atom,
• R45 represents a cyano group,
• R46 represents a hydrogen atom, and
• R48 represents —CO—CH2—O—H.