Disclosed is a compound represented by the general formula (I) below which has a strong COMT inhibitory effect, or a pharmacologically acceptable salt thereof. Also disclosed are a pharmaceutical composition containing such a compound or a pharmacologically acceptable salt thereof, and a use of those. (In the formula, R1 and R2 independently represent a hydrogen, a lower acyl, a lower alkoxycarbonyl or the like； R3 represents a halogen, a halo-lower alkyl, a cyano or the like； R4 represents a hydrogen, a lower alkyl or the like； and R5 and R6 independently represent a hydrogen, an alkyl, a cycloalkyl, a heterocycloalkyl, a halo-lower alkyl, an optionally substituted aryl, an optionally substituted heteroaryl or the like.)
