Abstract: For use in therapy a chemical compound of formula (I), wherein R1 to R3 are independently selected from hydrogen and alkyl; R4 to R7 are independently selected from hydrogen, halogen, hydroxy, alkyl, aryl, heterocyclyl, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfoxyl, alkylsulfonyl, arylsulfoxyl, arylsulfonyl, amino, monoalkylamino, dialkylamino, nitro, cyano, carboxaldehyde, alkylcarbonyl, arylcarbonyl, aminocarbonyl, monoalkylaminocarbonyl, dialkylaminocarbonyl, alkoxycarbonylamino, aminocarbonyloxy, monoalkylaminocarbonyloxy, dialkylaminocarbonyloxy, monoalkylaminocarbonylamino and dialkylaminocarbonylamino, wherein at least one of R4 to R7 is a substituent group other than hydrogen, and pharmaceutically acceptable salts and prodrugs thereof, particularly for the treatment of disorders of the central nervous system; damage to the central nervous system; cardiovascular disorders; gastrointestinal disorders; diabetes insipidus, and sleep apnea, and especially for the treatment of obesit