β-SECRETASE INHIBITOR

PROBLEM TO BE SOLVED: To develop a compound having excellent β-secretase-inhibiting activities and capable of being satisfied as a medicine. SOLUTION: This β-secretase inhibitor contains a compound represented by the formula [wherein, Ar is an aromatic group; X is a divalent group selected from O, S, CO, SO, SO2, NR8, CONR8, SO2NR8 and COO (wherein, R8 is hydrogen atom, or the like), a divalent 1-6C aliphatic hydrocarbon group which may include one or two of the divalent groups, or a bond; Y is a divalent group selected from O, S, CO, SO, SO2, NR8, CONR8, SO2NR8 and COO, or a divalent 1-6C aliphatic hydrocarbon group which may include one or two of the divalent groups; R1 and R2 are each hydrogen atom, a hydrocarbon group, or the like; and A-ring is a ring which may have the other substituent] or a salt thereof.