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.
