Provided is a compound having a serotonin 5-HT2C receptor activating action.A compound represented by the formula (I0):wherein each symbol is as defined in the specification, or a salt thereof.本發明提供一種血清素5-HT2C受體活化作用之化合物。式(I0)所示化合物或其鹽如下:式中,各符號如說明書中所定義。