Therapeutic agents

Tetrahydroisoquinoline compounds of formula I I and pharmaceutically acceptable salts thereof, in which: R1 represents one or more substituents selected from H, halo, hydroxy, alkyl (optionally substituted by hydroxy), alkoxy, alkylthio, alkylsulphinyl, alkyl-sulphonyl, nitro, cyano, polyhaloalkyl, polyhaloalkoxy, phenyl (optionally substituted by one or more of halo, alkyl or alkoxy), or R1 is optionally alkylated carbamoyl; R2 represents a saturated or unsaturated aliphatic group optionally substituted by hydroxy or alkoxy; E represents an alkylene chain optionally substituted by one or more alkyl groups; and G represents (a) optionally substituted saturated or unsaturated alicyclic group containing 3 to 8 carbon atoms, or (b) optionally substituted saturated or unsaturated aliphatic chain containing 1 to 12 carbon atoms, or (c) optionally substituted 5 or 6 membered heterocyclic ring containing one or more N or O atoms or SOn groups in which n is 0, 1 or 2; and O-acylated derivatives thereof which provide lipophilic esters have utility in analgesia or in the treatment of psychoses (e.g. schizophrenia), Parkinson's disease, Lesch-Nyan syndrome, attention deficit disorder or cognitive impairment or in the relief of drug dependence or tardive dyskinesia. Tetrahydroisoquinoline compounds of formula I I and pharmaceutically acceptable salts thereof, in which: R1 represents one or more substituents selected from H, halo, hydroxy, alkyl (optionally substituted by hydroxy), alkoxy, alkylthio, alkylsulphinyl, alkyl-sulphonyl, nitro, cyano, polyhaloalkyl, polyhaloalkoxy, phenyl (optionally substituted by one or more of halo, alkyl or alkoxy), or R1 is optionally alkylated carbamoyl; R2 represents a saturated or unsaturated aliphatic group optionally substituted by hydroxy or alkoxy; E represents an alkylene chain optionally substituted by one or more alkyl groups; and G represents (a) optionally substituted saturated or unsaturated alicyclic group containing 3 to 8 carbon atoms, or (b) optionally substituted saturated or unsaturated aliphatic chain containing 1 to 12 carbon atoms, or (c) optionally substituted 5 or 6 membered heterocyclic ring containing one or more N or O atoms or SOn groups in which n is 0, 1 or 2; and O-acylated derivatives thereof which provide lipophilic esters have utility in analgesia or in the treatment of psychoses (e.g. schizophrenia), Parkinson's disease, Lesch-Nyan syndrome, attention deficit disorder or cognitive impairment or in the