The present invention provides a compound which has an effect of inhibiting amyloid βproduction, especially an effect of inhibiting BACE1, and which is useful as a therapeutic or prophylactic agent for diseases induced by production, secretion and/or deposition of amyloid βproteins.A compound of Formula (I)wherein R3 is each independently alkyl optionally substituted with halogen, cyano, alkyloxy, haloalkyloxy or non-aromatic carbocyclyl, or the like； t is integer from 0 to 3； R5 is a hydrogen atom or halogen； R6 is selected from the group consisting of a hydrogen atom, halogen, and substituted or unsubstituted alkyl；ring B is a substituted or unsubstituted pyrazine or the like； or a pharmaceutically acceptable salt thereof.本發明提供一種化合物，其具有抑制類澱粉β蛋白產生的功效，尤其是抑制BACE1的功效，及其可使用作為由類澱粉β蛋白的產生、分泌及/或沈積所誘發的疾病之治療劑或預防劑。一種式(I)化合物，其中R3各自獨立地為視需要經以鹵素、氰基、烷基氧基、鹵烷基氧基、或非芳香族碳環基取代的烷基等；t為0至3之整數；R5為氫原子或鹵素；R6係選自於由氫原子、鹵素、及經取代或未經取代烷基所組成的組群；環B為經取代或未經取代之吡等；或其醫藥上可接受之鹽。
