. . . " 2. The compound or the pharmaceutically acceptable salt thereof according to claim 1, wherein Z is a hydrogen atom, C.sub.1-6alkyl, C.sub.3-9cycloalkyl, hydroxyC.sub.1-6alkyl, hydroxyC.sub.1-6alkoxyC.sub.1-6alkyl, C.sub.1-6alkoxyC.sub.1-6alkyl," . .