Patent ID: 7622598

Claim:
A compound represented by formula (I), an optical isomer thereof, a pharmaceutically acceptable salt thereof, wherein X is a hydrogen atom or a halogen atom; R 1 is a hydrogen atom or —(C n H 2n )—R′ (wherein n is an integer of 1 to 5; and R′ is a hydrogen atom, a group COOR″ or —COR′″ of a substituent on any one of the n carbon atoms, wherein R″ is a hydrogen atom or a C 1-4 alkyl group; and R′″ is a pyridyl group, an amino group substituted with a C 1-4 alkyl group, a phenoxyalkyl group having a halogen atom on the carbon atoms of the benzene ring or a phenyl group having a C 1-4 alkoxy group or a C 1-4 alkoxycarbonyl group on the carbon atoms of the benzene ring); R 2 is a hydrogen atom or a C 1-4 alkyl group; R 3 is —CHO or —COOH; and R 4 is —CH═CH—(CH 2 ) p —CH 3 (wherein p is an integer of 1 to 12), —CH(OH)—(CH 2 ) q —CH 3 (wherein q is an integer of 1 to 13), —CH(OH)—CH 2 —CH(CH 3 )—(CH 2 ) 2 —CH═C(CH 3 ) 2 , —CH═CH—CH(CH 3 )—(CH 2 ) 3 —CH(CH 3 ) 2 , —(CH 2 ) 2 —CH(CH 3 )—(CH 2 ) 3 —CH(CH 3 ) 2, or —(CH 2 ) 8 —CH 3 ].