The present invention relates to a compound represented by Formula [I] wherein represents an aromatic carbo- or heterocyclic ring which may have a substituent; Cy represents a mono-, bi- or tricyclic aliphatic carbocyclic group having 3 to 20 carbon atoms, which may have a substituent; represents a mono- or bicyclic aliphatic nitrogen-containing heterocyclic group having 3 to 14 carbon atoms, which may have a substituent; R1 represents a hydrogen atom, a lower alkenyl group, a lower alkynyl group, a cyclo(lower alkyl) group, an amino group, a lower alkylamino group, a di(lower alkyl)-amino group, a hydroxyl group, a lower alkoxy group, a carboxyl group, a lower alkoxycarbonyl group, a carbamoyl group, a lower alkylcarbamoyl group or a di(lower alkyl)carbamoyl group, or a lower alkyl group which may have a substituent; and R2 represents a hydrogen atom or a lower alkyl group, a salt or ester thereof, a production process for the same, and an analgesic, a reliever against tolerance to a narcotic analgesic represented by morphine, a reliever against dependence on a narcotic analgesic represented by morphine, an analgesic enhancer, an antiobestic, a drug for ameliorating brain function, a remedy for schizophrenia, a remedy for Parkinsonism, a remedy for chorea, an antidepressant, a remedy for diabetes insipidus, a remedy for polyuria, or a remedy for hypotension, comprising an effective ingredient of the same.