PROBLEM TO BE SOLVED: To provide therapeutic or preventive agents for various diseases or symptoms associated with a serotonin 4 receptor (particularly, neuropsychiatric diseases such as Alzheimer-type dementia).SOLUTION: The present invention provides a compound represented by formula (1) or a pharmaceutically acceptable salt thereof. In the formula (1), Het represents formula (Het-1) or the like, A represents formula (A-1) or the like, B represents (B-1) or the like, Rrepresents a hydrogen atom, an alkyl group or the like, R, R, Rand Rrepresent a hydrogen atom, a halogen atom, an alkyl group or the like, Rand Rrepresent a hydrogen atom, an alkyl group or the like, and l represents an integer of 0-4.SELECTED DRAWING: None【課題】セロトニン４受容体が関与する各種疾患又は症状（特にアルツハイマー型認知症等の精神神経系疾患）の治療剤又は予防剤を提供すること。【解決手段】式（１）：[式中、Ｈｅｔは式(Ｈｅｔ－１)等を、Ａは式(Ａ－１)等を、Ｂは（Ｂ－１）等を表し、Ｒ１Ａは水素原子、アルキル基等を表し、Ｒ２Ａ、Ｒ５、Ｒ６およびＲ７は水素原子、ハロゲン原子、アルキル基等を表し、Ｒ８およびＲ９は水素原子、アルキル基等を表し、ｌは０～４の整数を表す。] で表される化合物またはその製薬的に許容される塩を提供する。【選択図】なし
