Problems to be solved are to provide novel low-molecular compounds which exhibit calcium receptor antagonist activity, and which are highly safe and orally administrable. As a means for solving the problems, compounds having the Formula (I) or pharmaceutically acceptable salts thereof are provided.[in the formula, the substituent groups are defined as follows. R1 and R2a, R2b : a hydrogen atom, etc. R3: a methyl group, an ethyl group, etc. Z: a carboxy group, etc. Ar: a phenyl group, etc. A: a single bond, etc. B: a single bond, etc. n: 0 or 1. m: an integer of 0 to 6.]
