Having an affinity against serotonine receptors, compound (I) shown below is useful as a therapeutic agent against various kinds of diseases of central nervous systems; (wherein R1 is hydrogen; R2 is hydrogen or lower alkyl; R3 is hydrogen, —COOR12 and so on; R4 is hydrogen, lower alkyl and so on, or R3 and R4 taken together may form ═O or ═S; R5 is hydrogen, or R3 and R5 taken together may form a bond; R6 is hydrogen, —COOR24 and so on; R7 is hydrogen, halogen, lower alkyl and so on; R8 is hydrogen, lower alkyl, cycloalkyl and so on; R9, R10 and R11 are each independently hydrogen, halogen, lower alkyl and so on).