4-Substituted piperidine compound

A compound represented by the formula:

• 21
• (in the formula, R1 represents any one of group selected from the group consisting of the formulae:
• 22 23
• (wherein, R3, R4, R5 and R6 are the same as or different from each other and each represents a hydrogen atom, a halogen atom, a hydroxyl group, an optionally substituted hydrocarbon group, an optionally substituted C1-6 alkoxy group, a C1-6 acyl group, a nitro group, an optionally substituted amino group, an optionally substituted amide group, a mercapto group or a C1-6 thioalkoxy group;
• R7 represents a hydrogen atom or a C1-6 alkyl group;
• the partial structure represents a single bond or a double bond;
• m is 0 or an integer from 1 to 6;
• and p represents an integer of 1 or 2);
• and R2 represents a hydrogen atom, an optionally substituted C1-6 alkyl group, an optionally substituted C2-6 alkenyl group or an optionally substituted C2-6 alkynyl group), a salt thereof or a hydrate of them.