The invention provides compounds represented by the general formula (I) whichare useful as remedies for diseases induced by the production, secretion, ordeposition of amyloid β protein. Compounds represented by the generalformula (I)； pharmaceutically acceptable salts thereof； or solvates of both: (I) wherein A is an optionally substituted carbocyclic group or anoptionally substituted heterocyclic group； R is optionally substitutedlower alkyl, optionally substituted lower alkenyl, or optionally substitutedlower alkynyl； R and R are each independently hydrogen,optionally substituted lower alkyl, or optionally substituted acyl； and R,R, R and R are each independently hydrogen,halogeno, hydroxy, optionally substituted lower alkyl, or the like.
