Novel compounds below are useful for preventing or treating diseases caused by protozoans. At least one of a compound represented by Formula (I)(wherein, X represents a hydrogen atom or a halogen atom； R1 represents a hydrogen atom； R2 represents a hydrogen atom or a C1-7 alkyl group； R3 represents —CHO, —C(═O)R5, —COOR5 (wherein R5 represents a C1-7 alkyl group), —CH2OH or —COOH； and R4 represents a C1-16 alkyl group having one or more substituents on a terminal carbon atom and/or non-terminal carbon atom(s), a C2-16 alkenyl group having one or more substituents on a terminal carbon atom and/or non-terminal carbon atom(s), or a C2-16 alkynyl group having one or more substituents on a terminal carbon atom and/or non-terminal carbon atom(s)), an optical isomer thereof, and a pharmaceutically acceptable salt is used.
