PROBLEM TO BE SOLVED: To provide pharmaceuticals to inhibit formation of amyloid β (Aβ) peptides for treatment and/or prevention of Aβ-related pathologies such as Alzheimer's disease, Down's syndrome and β-amyloid angiopathy.SOLUTION: The present invention relates to compounds represented by formula (I) or pharmaceutically acceptable salts thereof. The present invention also relates to pharmaceutical compositions comprising the compounds or pharmaceutically acceptable salts thereof for treating and/or preventing cerebral amyloid angiopathy or hereditary cerebral hemorrhage, disorders associated with cognitive impairment such as MCI ("mild cognitive impairment"), Alzheimer's disease, memory loss, attention deficit symptoms associated with Alzheimer's disease, neurodegeneration associated with diseases such as Alzheimer's disease or dementia including dementia of mixed vascular and degenerative origin, pre-senile dementia, senile dementia and dementia associated with Parkinson's disease, and progressive supranuclear palsy or cortical basal degeneration.SELECTED DRAWING: None【課題】アミロイドβ（Ａβ）ペプチドの形成を阻害し、Ａβ関連の病理、例えばアルツハイマー病、ダウン症候群及びβアミロイド血管症等の治療及び／又は予防のための薬剤の提供。【解決手段】式（Ｉ）で表される化合物又はその薬学的に許容しうる塩。脳アミロイド血管症又は遺伝性脳出血、認知障害に関連する障害、例えば、ＭＣＩ（「軽度認知障害」）、アルツハイマー病、記憶喪失、アルツハイマー病に関連する注意欠陥症状、アルツハイマー病のような疾患に関連する神経変性又は血管及び変性由来の混合型認知症、初老期認知症、老年認知症及びパーキンソン病に関連する認知症を含む認知症、進行性核上性麻痺又は皮質基底核変性症の治療及び／又は予防のための、前記化合物又はその薬学的に許容しうる塩を含む医薬組成物。【選択図】なし
