PROBLEM TO BE SOLVED: To provide a novel compound having high lysine-specific demethylase (LSD) 1 inhibitory activity, high selectivity for LSD1 inhibition, and / or useful therapeutic effect for various diseases. SOLUTION: A compound represented by the formula (I), a stereoisomer thereof or a salt thereof, or a solvate thereof. [L is a single bond, alkylene, etc .； A is a substituted / unsubstituted cycloalkyl, substituted / unsubstituted heterocycle, etc.] [Selection diagram] None【課題】高いリジン特異的脱メチル化酵素（LSD）1阻害活性、LSD1阻害に対する高い選択性、及び／又は様々な疾患に対する有用な治療効果を有する新規化合物の提供。【解決手段】式（I）で表される化合物、その立体異性体若しくはそれらの塩、又はそれらの溶媒和物。［Lは単結合、アルキレン等；Ａは置換／非置換のシクロアルキル、置換／非置換のヘテロ環等］【選択図】なし
