Dihydroorotate dehydrogenase inhibitor

The present invention provides a novel dihydroorotate dehydrogenase inhibitor can be applied to various diseases. Formula (I) as an active ingredient (In the formula, X represents a halogen atom, R1 represents a hydrogen atom, R2 represents an alkyl group of 1-7 carbon atoms, R3 represents a -CHO, R4 is, -CH2-CH = C (CH3) -R0 (wherein R0 is the terminal carbon on and / or non-terminal alkyl group which may carbon atoms 1-12 may have a substituent on the carbon of compounds represented by such representative of), their optical isomers, and their pharmaceutically acceptable salts have excellent dihydroorotate dehydrogenase inhibitory activity, immunosuppressive agents, rheumatism therapeutic agent, anticancer agent, rejection reaction therapeutic agents, antiviral agents, anti H. It can be used as pylori agents and diabetes therapeutic agents and the like.