The present invention relates to novel compounds of formula (I) and their pharmaceutical compositions. In addition, the present invention relates to therapeutic methods for the treatment and/or prevention of A&bgr；-related pathologies such as Downs syndrome, &bgr；-amyloid angiopathy such as but not limited to cerebral amyloid angiopathy or hereditary cerebral hemorrhage, disorders associated with cognitive impairment such as but not limited to MCI (&ldquo；mild cognitive impairment&rdquo；), Alzheimer Disease, memory loss, attention deficit symptoms associated with Alzheimer disease, neurodegeneration associated with diseases such as Alzheimer disease or dementia including dementia of mixed vascular and degenerative origin, pre-senile dementia, senile dementia and dementia associated with Parkinson's disease, progressive supranuclear palsy or cortical basal degeneration.本発明は、式（Ｉ）の新規な化合物及びそれらの医薬組成物に関する。さらに本発明は、Ａβ関連病態、例えばダウン症候群、β－アミロイド血管症、例えば限定されないが脳アミロイド血管症若しくは遺伝性脳出血、認知機能障害に関連する疾患、例えば、限定されないがＭＣＩ（「軽度認知機能障害」）、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、又は混合型血管性起源及び変性起源の認知症、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大脳皮質基底核変性症の処置及び／又は予防のための治療方法に関する。【化１】
