Provided is a compound that is an NMDA receptor antagonist having a broader safety margin, and is useful as an agent for treating or preventing Alzheimers disease, cerebrovascular dementia, Parkinsons disease, ischemic apoplexy, or pain. A novel compound or a salt thereof, which is characterized in that it has an amino group and R 1 (lower alkyl, cycloalkyl, -lower alkylene-aryl, aryl which may be substituted, and the like) on carbon atoms of indane, cyclopenta[b]thiophene, cyclopenta[b]furan, cyclopenta[b]pyridine, or cyclopenta[c]pyridine ring, or 2,3-dihydrdo-1-benzofuran, 2,3-dihydrdo-1-benzothiophene, indoline ring, or the like, and has R 2 and R 3 (the same or different, each lower alkyl or aryl) on carbon atoms beside them, and an NMDA receptor antagonist comprising the same as an active component.
