| abstract |
Disclosed is a a therapeutic or prophylactic agent for diseases induced by the production, secretion and/or deposition of amyloid-β protein. Specifically disclosed is a compound represented by formula (I) (wherein R 1 , R 2a , R 2b , R 3 , R 4a , R 4b , ring A and the dotted line are as defined in the description), a pharmaceutically acceptable salt of the compound, or a solvate of the compound or the pharmaceutically acceptable salt. |