PROBLEM TO BE SOLVED: To provide a new compound or its pharmaceutically acceptable salt useful for preventing or treating diseases such as integrated dystonia, Alzheimer disease, cognitive dysfunction, dementia, anxiety disorder(such as global anxiety disorder, panic disorder, obsessive compulsive disorder, social anxiety disorder, post traumatic stress disorder, particular phobia, acute stress disorder), depression, drug dependence, convulsion, trembling, ache, Parkinson disease, attention-deficit/hyperactivity disorder, bipolar disorder, eating disorder or sleep disorder, based on inhibitory effect on glycine uptake.SOLUTION: There are provided a compound represented by the formula [I] or its pharmaceutically acceptable salt.【課題】本発明は、グリシン取り込み阻害作用に基づいた統合失調症、アルツハイマー病、認知機能障害、認知症、不安障害（全般性不安障害、パニック障害、強迫性障害、社会不安障害、外傷後ストレス障害、特定の恐怖症、急性ストレス障害等）、うつ病、薬物依存、痙攣、振戦、疼痛、パーキンソン病、注意欠陥・多動性障害、双極性障害、摂食障害、又は睡眠障害等の疾患の予防又は治療に有用な新規な化合物又はその医薬上許容される塩を提供することを目的とする。【解決手段】式［Ｉ］で表される化合物又はその医薬上許容される塩。【選択図】なし
