A composition having BACE 1 inhibitory activity containing a compound represented by the general formula (I)- wherein ring A is an optionally substituted carbocyclic group or an optionally substituted heterocyclic group； E is lower alkylene! X is S, O. or NR1； R1 is a hydrogen atom or lower alkyl； R2a, R2b, R3a, R3b, R4a and R4b is each independently a hydrogen atom, halogen, or hydroxy etc.； n and m are each independently an integer of 0 to 3； n+m is an integer of 0 to 3； R5 is a hydrogen atom or substituted lower alkyl； its pharmaceutically acceptable salt, or a solvate thereof.
