Provided is a compound which has calcium-sensitive receptor antagonistic activity, and which may be expected to be useful as an agent for the prevention and/or treatment of cardiac failure, pulmonary hypertension and the like, or a salt of said compound. The compound represented by formula (I) or a salt of said compound has calcium-sensitive receptor antagonistic activity, and may be expected to be useful as an agent for the prevention and/or treatment of cardiac failure, pulmonary hypertension and the like. [In the formula, each of the symbols is as described in the description.]
