abstract |
The present invention provide a medicament for treating the diseases induced by production, secretion or deposition of amyloid-β proteins, for example, a compound of the following formula (I) wherein R 1 R 2a , R 2b , R 3a , R 3b R 4a , R 4b , ring A, Y and the dotted line are defined in the specification, its pharmaceutically acceptable salt or a solvate thereof. |