A BACE 1 inhibitor containing, as an active ingredient, any one of a compound represented by the formula (I): (wherein ring A is an optionally substituted carbocyclic group or optionally substituted heterocyclic group； E is lower alkylene, etc.； X is S, O, or NR (R is hydrogen or lower alkyl)； R, R, R, R, R, and R each independently is hydrogen, halogeno, hydroxy, etc.； n and m each independently is an integer of 0-3, provided that n+m is 1-3； and R is hydrogen, optionally substituted lower alkyl, etc.), a pharmaceutically acceptable salt thereof, and a solvate of either.
