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 general formula, R1, R2a, and R2b are each a hydrogen atom or the like R3 is methyl, ethyl, or the like Z is carboxyl or the like Ar is phenyl or the like A is a single bond or the like B is a single bond or the like n is 0 or 1 and m is an integer of 0 to 6.
