The present invention relates to a compound or a pharmacologically acceptable salt thereof having excellent tissue non-specific alkaline phosphatase inhibitory activity. The present invention provides a compound represented by the formula (I) : wherein R1 represents a hydrogen atom, an optionally substituted Cl-6 alkyl group, or the like, R2 and R3 are the same or different and each represent a hydrogen atom, an optionally substituted Cl-6 alkyl group, or the like, R4 and R5 are the same or different and each represent a hydrogen atom, an optionally substituted Cl-6 alkyl group, or the like, R6 represents a hydrogen atom or the like, each R7 may be the same or different and may each represent an optionally substituted Cl-6 alkoxy group or the like, X represents -CH=, -C(-R7)=, or -N=, and m represents 1 to 4, or a pharmacologically acceptable salt thereof.
