Patent Publication Number: US-2009221643-A1

Title: 4-phenyl-3-(2-propylsulfonylamino) tetrahydrofuran derivatives which potentiate glutamate receptors and are useful in the treatment of schizophrenia

Description:
This invention relates to novel compounds which potentiate the glutamate receptor. The invention also relates to the use of the compounds in treating diseases and conditions mediated by potentiation of the glutamate receptor, compositions containing the derivatives and processes for their preparation. 
     Glutamate receptors, which mediate the majority of fast excitatory neurotransmission in the mammalian central nervous system (CNS), are activated by the excitatory amino acid, L-glutamate (for review see Watkins J C, Krogsgaard-Larsen P, Honore T (1990) Trends Pharmacol Sci 11: 25-33). 
     Glutamate receptors can be divided into two distinct families. The G-protein or second messenger-linked “metabotropic” glutamate receptor family which can be subdivided into three groups (Group I, mGlu1 and mGlu5; Group II, mGlu2 and mGlu3; Group III, mGlu4, mGlu6, mGlu7, mGlu8) based on sequence homology and intracellular transduction mechanisms (for review see Conn P J and Pinn J P (1997) Ann Rev Pharmacol Toxicol 37: 205-237). The “ionotropic” glutamate receptor family, which directly couple to ligand-gated cation channels, can be subdivided into at least three subtypes based on depolarizing activation by selective agonists, N-methyl-D-aspartate (NMDA), α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and kainic acid (KA) (for review see Dingledine R, Borges K, Bowie, Traynelis S (1999) 51: 7-61). 
     Native AMPA receptors (AMPAR) exist as heterotetramers consisting of combinations of four different protein subunits (GluR1-4) (for review see Bettler B and Muller C (1995) 34: 123-139.). Receptor subunit diversity is increased further as each subunit can undergo alternative splicing of a 38 amino acid sequence in the extracellular region just before the fourth membrane spanning domain M4. Such editing results in so-called ‘flip’ and ‘flop’ receptor isoforms which differ in kinetic and pharmacological properties (Sommer B, Keinanen K, Verdoon T A, Wisden W, Burnashev N, Herb A, Kohler M, Takagi T, Sakmann B, Seeburg P H (1990) Science 249: 1580-1585). 
     Additionally, post-transcriptional editing of GluR2 mRNA changes a neutral glutamine to a positively charged arginine within M2. In normal humans &gt;99% GluR2 is edited in this way. AMPAR containing such edited GluR2 subunit exhibit low calcium permeability (Burnachev N, Monyer H, Seeburg P H, Sakmann B (1992) Neuron 8: 189-198). There is a suggestion, however, that the number of AMPAR with high calcium permeability is elevated in certain disease-associated conditions (Weiss J H, and Sensi S L (2000) Trends in Neurosci 23: 365-371). 
     AMPAR depolarization removes voltage dependent Mg 2+  block of NMDA receptors which in turn leads to NMDA receptor activation, an integral stage in the induction of Long-Term Potentiation (“LTP”) (Bliss T V P, Collingridge G L (1993) Nature 361: 31-9). LTP is a physiological measure of increased synaptic strength following a repetitive stimulus or activity, such as occurs during learning. 
     It has been reported that direct activation of glutamate receptors by agonists, in conditions where glutamate receptor function is reduced, increases the risk of excitotoxicity and additional neuronal damage. AMPAR positive allosteric modulators do not activate the receptor directly. However, when the ligand (L-glutamate or AMPA) is present AMPAR modulators increase receptor activity. Thus, AMPA receptor modulators enhance synaptic function when glutamate is released and is able to bind at post-synaptic receptor sites. 
     Compounds which act as AMPAR positive allosteric modulators have been shown to increase ligand affinity for the receptor (Arai A, Guidotti A, Costa E, Lynch G (1996) Neuroreport. 7: 2211-5.); reduce receptor desensitization and reduce receptor deactivation (Arai A C, Kessler M, Rogers G, Lynch G (2000) 58: 802-813) and facilitate the induction of LTP both in vitro (Arai A, Guidotti A, Costa E, Lynch G (1996) 7: 2211-5.) and in vivo (Staubli U, Perez Y, Xu F, Rogers G, Ingvar M, Stone-Elander S, Lynch G (1994) Proc Natl Acad Sci 91: 11158-11162). Such compounds also enhance the learning and performance of various cognitive tasks in rodent (Zivkovic I, Thompson D M, Bertolino M, Uzunov D, DiBella M, Costa E, Guidotti A (1995) JPET 272: 300-309, Lebrun C, Pilliere E, Lestage P (2000) Eu J Pharmacol 401: 205-212), sub-human primate (Thompson D M, Guidotti A, DiBella M, Costa E (1995) Proc Natl Acad Sci 92: 7667-7671) and man (Ingvar M, Ambros-Ingerson J, Davis M, Granger R, Kessler M, Rogers G A, Schehr R S, Lynch G (1997) Exp Neurol 146: 553-559). 
     Compounds which act as AMPAR positive allosteric modulators are known, for example in international patent application WO2006/015828. We have discovered a class of novel compounds that also potentiate the AMPA receptor. 
     According to a first aspect, the invention provides a compound of formula (I), or a salt, or solvate thereof: 
     
       
         
         
             
             
         
       
     
     wherein:
 
Ar is selected from phenyl, pyridyl and thienyl, each of which is optionally substituted with one or more groups Y;
 
each Y group is independently selected from the group consisting of: halo, C 1-4 alkyl, haloC 1-4 alkyl, C 1-4 alkoxy, cyano, C(O)C 1-4 alkyl, NHSO 2 C 1-4 alkyl, NMeSO 2 C 1-4 alkyl, NHCOC 1-4 alkyl, NMeCOC 1-4 alkyl, SOC 1-4 alkyl, SO 2 C 1-4 alkyl and CO 2 C 1-4 alkyl, or two Y groups together form a cyclic group —O(CH 2 )O—.
 
     As used herein, the terms “halogen” and its abbreviation “halo” refer to fluorine, chlorine, bromine, or iodine. 
     C 1-4 alkyl may be a straight chain or branched alkyl group. For example, a C 1-4 alkyl group may be selected from methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl or t-butyl. For example, C 1-4 alkyl is methyl, or “Me”. 
     As used herein, the term “C 1-4 alkoxy” refers to the group —O—C 1-4 alkyl wherein C 1 -C 4 alkyl is as defined above. 
     As used herein, the term “haloC 1-4 alkyl” refers to a C 1-4 alkyl group as defined above which is substituted with any number of fluorine, chlorine, bromine, or iodine atoms, including with mixtures of those atoms. A haloC 1-4 alkyl group may, for example contain 1, 2 or 3 halogen atoms. For example, a haloC 1-4 alkyl group may have all hydrogen atoms replaced with halogen atoms. Examples of haloC 1-4 alkyl groups include fluoromethyl, difluoromethyl and trifluoromethyl. 
     In an embodiment the salt or solvate of the compound of formula (I) is a pharmaceutically acceptable salt or solvate. In one embodiment, the invention provides a compound of formula (I), or a pharmaceutically acceptable salt or solvate thereof. 
     In an embodiment, Ar is selected from phenyl and pyridyl. In a further embodiment, Ar is pyridyl. 
     In an embodiment when Ar is a pyridyl group, the pyridyl group is positioned with the ring nitrogen meta or para to the point of attachment to the remainder of the molecule. In a further embodiment, the pyridyl nitrogen is meta to the point of attachment to the remainder of the molecule. 
     In one embodiment, zero, one, two or three Y groups are present. 
     In an embodiment, at least one Y group is present. In an embodiment, each Y group is independently selected from halo, methyl, cyano and C(O)CH 3  or two Y groups together form a cyclic group —O(CH 2 )O—. In an embodiment, each Y group is selected from is independently selected from the group consisting of: fluoro, chloro, methyl, cyano and C(O)CH 3 . In an embodiment, the molecule has one Y group. In one embodiment, the one Y group is selected from fluorine and methyl. In one embodiment, the one Y group is fluorine. 
     Each substituent Y may be positioned ortho, meta or para to the point of attachment of the group Ar to the remainder of the molecule. In one embodiment a Y group is positioned para or meta with respect to the point of attachment of the Ar group to the main structure of the molecule. In a further embodiment, a Y group is positioned meta with respect to the point of attachment of the Ar group to the main structure of the molecule. 
     Because of the presence of the tetrahydrofuran ring, compounds of formula (I) possess at least two chiral centres, namely the attachment points of the sulphonamide and the phenyl ring on the tetrahydrofuran ring. The tetrahydrofuran compounds may exist in four stereoisomers—a pair of diastereomers (cis and trans), each comprising a pair of enantiomers with respect to the chiral centres in the tetrahydrofuran. 
     In one embodiment, compounds of formula (I) have the cis configuration as shown in formula (Ia): 
     
       
         
         
             
             
         
       
     
     It will be appreciated, in common with most biologically active molecules, that the level of biological activity may vary between the enantiomers of a given molecule. It is intended that the scope of the invention includes both enantiomers and all mixtures thereof, including but not limited to racemic mixtures, which demonstrate appropriate biological activity with reference to the procedures described herein. 
     In one embodiment a compound of the invention in chiral form has at least 80% e.e. In another a compound of the invention in chiral form has at least 90% e.e., for example at least 95% e.e. In another embodiment the isomers correspond to at least 98% e.e, for example at least 99% e.e. 
     It will be appreciated that the present invention is intended to include compounds having any combination of the groups listed hereinbefore. 
     It will be understood that, where appropriate, an embodiment described above for one part of the invention may be combined with an embodiment of another part of the invention. 
     Examples of compounds of formula (I) include:
     N-{cis-4-[4-(6-fluoro-3-pyridinyl)phenyl]tetrahydro-3-furanyl}-2-propanesulfonamide   N-{cis-4-[4-(6-methyl-3-pyridinyl)phenyl]tetrahydro-3-furanyl}-2-propanesulfonamide   N-{cis-4-[4-(5-fluoro-2-pyridinyl)phenyl]tetrahydro-3-furanyl}-2-propanesulfonamide   N-{cis-4-[4-(5-fluoro-3-pyridinyl)phenyl]tetrahydro-3-furanyl}-2-propanesulfonamide   N-{cis-4-[4-(5-chloro-2-pyridinyl)phenyl]tetrahydro-3-furanyl}-2-propanesulfonamide   N-{cis-4-[4-(5-methyl-3-pyridinyl)phenyl]tetrahydro-3-furanyl}-2-propanesulfonamide   N-[cis-4-(4′-fluoro-4-biphenylyl)tetrahydro-3-furanyl]-2-propanesulfonamide   N-[cis-4-(4′-cyano-4-biphenylyl)tetrahydro-3-furanyl]-2-propanesulfonamide   N-[cis-4-(3′-acetyl-4-biphenylyl)tetrahydro-3-furanyl]-2-propanesulfonamide   N-{cis-4-[4-(1,3-benzodioxol-5-yl)phenyl]tetrahydro-3-furanyl}-2-propanesulfonamide   N-{cis-4-[4-(3-thienyl)phenyl]tetrahydro-3-furanyl}-2-propanesulfonamide   N-{cis-4-[4-(2-thienyl)phenyl]tetrahydro-3-furanyl}-2-propanesulfonamide
 
and salts and solvates thereof.
   

     For the avoidance of doubt, unless otherwise indicated, the term substituted means substituted by one or more defined groups. In the case where groups may be selected from a number of alternative groups, the selected groups may be the same or different. For the avoidance of doubt, the term independently means that where more than one substituent is selected from a number of possible substituents, those substituents may be the same or different. 
     As used herein, the term “salt” refers to any salt of a compound according to the present invention prepared from an inorganic or organic acid or base, quaternary ammonium salts and internally formed salts. Pharmaceutically acceptable salts are particularly suitable for medical applications because of their greater aqueous solubility relative to the parent compounds. Such salts must clearly have a pharmaceutically acceptable anion or cation. Suitably pharmaceutically acceptable salts of the compounds of the present invention include acid addition salts formed with inorganic acids such as hydrochloric, hydrobromic, hydroiodic, phosphoric, metaphosphoric, nitric and sulfuric acids, and with organic acids, such as tartaric, acetic, trifluoroacetic, citric, malic, lactic, fumaric, benzoic, formic, propionic, glycolic, gluconic, maleic, succinic, (1S)-(−)-10-camphorsulphonic, (1S)-(+)-10-camphorsulphonic, isothionic, mucic, gentisic, isonicotinic, saccharic, glucuronic, furoic, glutamic, ascorbic, anthranilic, salicylic, phenylacetic, mandelic, embonic (pamoic), methanesulfonic, ethanesulfonic, pantothenic, stearic, sulfinilic, alginic, galacturonic and arylsulfonic, for example naphthalene-1,5-disulphonic, naphthalene-1,3-disulphonic, benzenesulfonic, and p-toluenesulfonic, acids; base addition salts formed with alkali metals and alkaline earth metals and organic bases such as N,N-dibenzylethylenediamine, chloroprocaine, choline, diethanolamine, ethylenediamine, meglumaine (N-methylglucamine), lysine and procaine; and internally formed salts. Salts having a non-pharmaceutically acceptable anion or cation are within the scope of the invention as useful intermediates for the preparation of pharmaceutically acceptable salts and/or for use in non-therapeutic, for example, in vitro, situations. The salts may have any suitable stoichiometry. For example, a salt may have 1:1 or 2:1 stoichiometry. Non-integral stoichiometry ratios are also possible. 
     Furthermore, some of the crystalline forms of the compounds of structure (I) may exist as polymorphs, which are included in the present invention. Some of the compounds of this invention may be crystallised or recrystallised from solvents such as aqueous and organic solvents. In such cases solvates may be formed. This invention includes within its scope stoichiometric solvates as well as compounds containing variable amounts of solvent, where non-stoichiometric solvates may be produced by processes such as lyophilisation. In one embodiment, the compounds of the present invention are provided in the form of stoichiometric and non-stoichiometric hydrates. 
     It will be appreciated by those skilled in the art that certain protected derivatives of compounds of formula (I), which may be made prior to a final deprotection stage, may not possess pharmacological activity as such, but may, in certain instances, be administered orally or parenterally and thereafter metabolised in the body to form compounds of the invention which are pharmacologically active. Such derivatives may therefore be described as “prodrugs”. Further, certain compounds of the invention may be administered as prodrugs. Examples of pro-drug forms for certain compounds of the present invention are described in Drugs of Today, Volume 19, Number 9, 1983, pp 499-538 and in Topics in Chemistry, Chapter 31, pp 306-316 and in “Design of Prodrugs” by H. Bundgaard, Elsevier, 1985, Chapter 1 (the disclosures in which documents are incorporated herein by reference). It will further be appreciated by those skilled in the art, that certain moieties, known to those skilled in the art as “pro-moieties”, for example as described by H. Bundgaard in “Design of Prodrugs” (the disclosure in which document is incorporated herein by reference) may be placed on appropriate functionalities when such functionalities are present within compounds of the invention. Examples of prodrugs for certain compounds of the invention include: amides, carbamates and phosphamides. The present invention therefore also provides a prodrug of a compound of formula (I) or a salt or solvate thereof. 
     Hereinafter, compounds of formula (I), their salts and their solvates defined in any aspect of the invention (except Intermediate compounds in chemical processes) are referred to as “compounds of the invention”. 
     Since the compounds of the invention are intended for use in pharmaceutical compositions it will readily be understood that they may each be provided in substantially pure form, for example at least 85%, or at least 98% pure or at least 99% pure (% are on a weight for weight basis). Impure preparations of the compounds may be used for preparing the more pure forms used in the pharmaceutical compositions. 
     Compounds of the invention may be prepared in a variety of ways. In the following reaction schemes and hereafter, unless otherwise stated Ar and Y are as defined in the first aspect. These processes form further aspects of the invention. 
     Throughout the specification, general formulae are designated by Roman numerals (I), (II), (III), (IV) etc. Subsets of these general formulae are defined as (Ia), (Ib), (Ic) etc. . . . (IVa), (IVb), (IVc) etc. 
     Compounds of general formula (I) may be prepared from compounds of formula (II) by reaction with compounds of formula (III) according to reaction scheme 1. Typical reaction conditions comprise adding iPrSO 2 Cl (VIII) to a mixture of (II) and 1,8-diazabicyclo[5.4.0]undec-7-ene with cooling. 
     
       
         
         
             
             
         
       
     
     Alternatively compound of formula (I) may be prepared by coupling a compound of formula (III) where X is a leaving group such as halogen (for example chlorine, bromine or iodine) with a boronic acid derivative of formula (VI) according to reaction Scheme 2. Typical coupling conditions comprise heating a compound of formula (II), a compound of formula (III), a base (or potassium fluoride where the leaving group is chlorine), 2-(di-tert-butylphosphino)biphenyl and palladium (II) acetate in dry tetrahydrofuran at about 140 degC. The method of Scheme 2 is particularly suitable for compounds of the invention in which Ar is pyridyl. 
     
       
         
         
             
             
         
       
     
     Alternatively, a compound of formula (I) may be prepared by treating a boronate compound of formula (V) with a compound Ar—X (VI) where X is a leaving group such as halogen (for example bromine or iodine) as shown in Scheme 3. For example the boronate may be a 4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl compound as shown in Scheme 3. Typical reaction conditions comprise heating the boronate compound (V) with a compound of formula (VI), a base (or potassium fluoride where the leaving group is chlorine) and a suitable catalyst (for example a palladium catalyst, such as palladium (II) acetate of palladium tetrakis, which may be polymer-supported) in a suitable solvent (for example dry 1, 4-dioxane) at for example, about 90° C. Suitable bases include sodium carbonate solution. 
     The boronate compound (V) may be prepared by reaction of a compound of formula (III) with a suitable diboron compound. Typical coupling conditions comprise heating the compound of formula (III) (for example at approximately 90° C.) with the diboron compound (for example bis(pinacolato)diboron) in a suitable solvent (for example dioxane) in the presence of a suitable base (for example potassium acetate) to produce a compound of formula (V). 
     The method of Scheme 3 is particularly suitable for compounds of the invention in which Ar is phenyl, pyridyl or thienyl. 
     
       
         
         
             
             
         
       
     
     Compounds of general formula (II) (see scheme 1) may be prepared from compounds of formula (VI) according to reaction scheme 4, by reacting compounds of formula (VI) with indium metal at room temperature. 
     
       
         
         
             
             
         
       
     
     Compounds of formula (III) (see scheme 2) may be prepared from compounds of formula (VII) according to reaction scheme 5. Typical reaction conditions are adding isopropyl sulfonyl chloride (VIII) to an ice-cooled mixture of (VII) and a base (such as diisopropylamine) in a suitable solvent (such as dichloromethane) and then warming the mixture gradually to room temperature. 
     
       
         
         
             
             
         
       
     
     Compounds of formula (VII) may be prepared from a compound of formula (IX) according to reaction scheme 6. Typical reaction conditions are sequentially adding a suitable acid, such as trifluoromethanesulfonic acid, and an N-halosuccinimide (X), such as N-iodosuccinimide, to a cooled solution of the compound of formula (IX) in a suitable solvent and then warming the mixture gradually to room temperature. 
     
       
         
         
             
             
         
       
     
     The compound of formula (IX) may be prepared from a compound of formula (XIII), wherein P is a suitable protecting group, according to reaction scheme 7, by removal of the protecting group P according to known synthetic procedures. For example, for the compound (XIIIa), wherein P is benzyl, typical reaction conditions include hydrogenation, for example by reaction of a solution of compound (XIIIa) in a suitable solvent, such as methanol, with hydrogen in the presence of a suitable catalyst, for example Pd(OH) 2 /C, and optionally under pressure. 
     Compounds of formula (XIII) may be prepared from the compound of formula (XI). Typical reaction conditions include adding an amine of formula (XII) to a solution of the compound of formula (XII) in a solvent such as dichloromethane, and subsequently adding a suitable reducing agent. Suitable amine compounds (XII) include benzylamine. Suitable reducing agents include sodium triacetoxyborohydride in the presence of acetic acid. Due to steric hindrance by the phenyl group, simple reaction under these conditions leads to predominantly the cis isomer of compound (XIII). The trans isomer may be obtained by a suitable inversion step. 
     
       
         
         
             
             
         
       
     
     The compound of formula (XI) may be prepared by oxidation of the compound of formula (XV), according to reaction scheme 8. The compound of formula (XV) is treated with a suitable oxidising agent, such as TEMPO (2,2,6,6,-tetramethyl-1-piperidinyloxy) in the presence of trichloroisocyanuric acid. 
     The compound of formula (XV) may be prepared from the compound of formula (XIV), 3,6-dioxabicyclo[3.1.0]hexane. Typical reaction conditions include reacting phenyl magnesium bromide with copper iodide in a suitable solvent, followed by cooling of the reaction mixture and addition of a solution of the compound of formula (XIV) in a suitable solvent, then warming the mixture gradually to room temperature. Suitable solvents for the reaction include tetrahydrofuran. 
     
       
         
         
             
             
         
       
     
     Thus, the present invention also provides a process for preparing a compound of formula (I) or a salt or solvate thereof, the process comprising: 
     a) reacting a compound of formula (II): 
     
       
         
         
             
             
         
       
     
     wherein Ar is as defined for formula (I), with iPrSO 2 Cl (VII)
 
b) coupling a compound of formula (III) where X is a leaving group such as halogen (for example chlorine, bromine or iodine) with a boronic acid derivative of formula (IV)
 
     
       
         
         
             
             
         
       
     
     or
 
c) coupling a boronate compound of formula (V) with a compound Ar—X (VI) where X is a leaving group such as halogen (for example bromine or iodine)
 
     
       
         
         
             
             
         
       
     
     and thereafter optionally:
         removing any protecting group(s); and/or   forming a salt or solvate; and/or   converting one compound of formula (I) to another compound of formula (I).       

     Further details for the preparation of compounds of formula (I) are found in the Examples section hereinafter. 
     The compounds of the invention may be prepared singly or as compound libraries comprising at least 2, for example 5 to 1,000 compounds, for example 10 to 100 compounds. Libraries of compounds of the invention may be prepared by a combinatorial ‘split and mix’ approach or by multiple parallel synthesis using either solution phase or solid phase chemistry, by procedures known to those skilled in the art. Thus according to a further aspect there is provided a compound library comprising at least 2 compounds of the invention. 
     The compounds of the present invention potentiate the glutamate receptor, and are thus considered to be useful for treating diseases and conditions which are mediated by the potentiation of the glutamate receptor. 
     It will be appreciated that the invention includes the following further aspects. The embodiments described in respect of the first aspect apply equally to each of these further aspects:
     i) a pharmaceutical composition comprising a compound of the invention and at least one carrier, diluent or excipient;   ii) the use of a compound of the invention in the manufacture of a medicament for treating a disease or condition mediated by a reduction or imbalance in glutamate receptor function in a mammal;   iii) a compound of the invention for use in treating a disease or condition mediated by a reduction or imbalance in glutamate receptor function in a mammal;   iv) a compound of the invention for use as a medicament;   v) a method of treatment of a disease or condition mediated by a reduction or imbalance in glutamate receptor function in a mammal comprising administering an effective amount of a compound of the invention;   vi) a combination product of a compound of the invention with an antipsychotic;   vii) a pharmaceutical composition comprising a combination product as defined in vi) above and at least one carrier, diluent or excipient;   viii) the use of a combination product as defined in vi) above in the manufacture of a medicament for treating a disease or condition mediated by a reduction or imbalance in glutamate receptor function in a mammal;   ix) a combination product as defined in vi) above for use in treating a disease or condition mediated by a reduction or imbalance in glutamate receptor function in a mammal;   x) a combination product as defined in vi) above for use as a medicament;   xi) a method of treatment of a disease or condition mediated by a reduction or imbalance in glutamate receptor function in a mammal comprising administering an effective amount of a combination product as defined in vi) above.   

     In the case of aspects ii), iii), v), viii), ix) and xi), relevant diseases or conditions are: psychosis and psychotic disorders (including schizophrenia, schizo-affective disorder, schizophreniform diseases, brief reactive psychosis, child onset schizophrenia, “schizophrenia-spectrum” disorders such as schizoid or schizotypal personality disorders, acute psychosis, alcohol psychosis, drug-induced psychosis, autism, delerium, mania (including acute mania), manic depressive psychosis, hallucination, endogenous psychosis, organic psychosyndrome, paranoid and delusional disorders, puerperal psychosis, and psychosis associated with neurodegenerative diseases such as Alzheimer&#39;s disease); cognitive impairment (e.g. the treatment of impairment of cognitive functions including attention, orientation, memory (i.e. memory disorders, amnesia, amnesic disorders and age-associated memory impairment) and language function, and including cognitive impairment as a result of stroke, Alzheimer&#39;s disease, Aids-related dementia or other dementia states, as well as other acute or sub-acute conditions that may cause cognitive decline such as delirium or depression (pseudodementia states) trauma, aging, stroke, neurodegeneration, drug-induced states, neurotoxic agents), mild cognitive impairment, age related cognitive impairment, autism related cognitive impairment, Down&#39;s syndrome, cognitive deficit related to psychosis, post-electroconvulsive treatment related cognitive disorders; anxiety disorders (including generalised anxiety disorder, social anxiety disorder, agitation, tension, social or emotional withdrawal in psychotic patients, panic disorder, and obsessive compulsive disorder); neurodegenerative diseases (such as Alzheimer&#39;s disease, amyotrophic lateral sclerosis, motor neurone disease and other motor disorders such as Parkinson&#39;s disease (including relief from locomotor deficits and/or motor disability, including slowly increasing disability in purposeful movement, tremors, bradykinesia, hyperkinesia (moderate and severe), akinesia, rigidity, disturbance of balance and co-ordination, and a disturbance of posture), dementia in Parkinson&#39;s disease, dementia in Huntington&#39;s disease, neuroleptic-induced Parkinsonism and tardive dyskinesias, neurodegeneration following stroke, cardiac arrest, pulmonary bypass, traumatic brain injury, spinal cord injury or the like, and demyelinating diseases such as multiple sclerosis and amyotrophic lateral sclerosis); depression (which term includes bipolar (manic) depression (including type I and type II), unipolar depression, single or recurrent major depressive episodes with or without psychotic features, catatonic features, melancholic features, atypical features (e.g. lethargy, over-eating/obesity, hypersomnia) or postpartum onset, seasonal affective disorder and dysthymia, depression-related anxiety, psychotic depression, and depressive disorders resulting from a general medical condition including, but not limited to, myocardial infarction, diabetes, miscarriage or abortion); post-traumatic stress syndrome; attention deficit disorder; attention deficit hyperactivity disorder; drug-induced (phencyclidine, ketamine and other dissociative anaesthetics, amphetamine and other psychostimulants and cocaine) disorders; Huntingdon&#39;s chorea; tardive dyskinesia; dystonia; myoclonus; spasticity; obesity; stroke; sexual dysfunction; sleep disorders, and some forms of epilepsy. 
     Within the context of the present invention, the terms describing the indications used herein are classified in the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, published by the American Psychiatric Association (DSM-IV) and/or the International Classification of Diseases, 10th Edition (ICD-10). The various subtypes of the disorders mentioned herein are contemplated as part of the present invention. Numbers in brackets after the listed diseases below refer to the classification code in DSM-IV. 
     Within the context of the present invention, the term “psychotic disorder” includes:— 
     Schizophrenia including the subtypes Paranoid Type (295.30), Disorganised Type (295.10), Catatonic Type (295.20), Undifferentiated Type (295.90) and Residual Type (295.60); Schizophreniform Disorder (295.40); Schizoaffective Disorder (295.70) including the subtypes Bipolar Type and Depressive Type; Delusional Disorder (297.1) including the subtypes Erotomanic Type, Grandiose Type, Jealous Type, Persecutory Type, Somatic Type, Mixed Type and Unspecified Type; Brief Psychotic Disorder (298.8); Shared Psychotic Disorder (297.3); Psychotic Disorder Due to a General Medical Condition including the subtypes With Delusions and With Hallucinations; Substance-Induced Psychotic Disorder including the subtypes With Delusions (293.81) and With Hallucinations (293.82); and Psychotic Disorder Not Otherwise Specified (298.9). 
     Compounds of the invention may also be of use in the treatment of the following disorders:— 
     Depression and mood disorders including Major Depressive Episode, Manic Episode, Mixed Episode and Hypomanic Episode; Depressive Disorders including Major Depressive Disorder, Dysthymic Disorder (300.4), Depressive Disorder Not Otherwise Specified (311); Bipolar Disorders including Bipolar I Disorder, Bipolar II Disorder (Recurrent Major Depressive Episodes with Hypomanic Episodes) (296.89), Cyclothymic Disorder (301.13) and Bipolar Disorder Not Otherwise Specified (296.80); Other Mood Disorders including Mood Disorder Due to a General Medical Condition (293.83) which includes the subtypes With Depressive Features, With Major Depressive-like Episode, With Manic Features and With Mixed Features), Substance-induced Mood Disorder (including the subtypes With Depressive Features, With Manic Features and With Mixed Features) and Mood Disorder Not Otherwise Specified (296.90): 
     Anxiety disorders including Panic Attack; Panic Disorder including Panic Disorder without Agoraphobia (300.01) and Panic Disorder with Agoraphobia (300.21); Agoraphobia; Agoraphobia Without History of Panic Disorder (300.22), Specific Phobia (300.29, formerly Simple Phobia) including the subtypes Animal Type, Natural Environment Type, Blood-Injection-injury Type, Situational Type and Other Type), Social Phobia (Social Anxiety Disorder, 300.23), Obsessive-Compulsive Disorder (300.3), Posttraumatic Stress Disorder (309.81), Acute Stress Disorder (308.3), Generalized Anxiety Disorder (300.02), Anxiety Disorder Due to a General Medical Condition (293.84), Substance-Induced Anxiety Disorder, Separation Anxiety Disorder (309.21), Adjustment Disorders with Anxiety (309.24) and Anxiety Disorder Not Otherwise Specified (300.00): 
     Substance-related disorders including Substance Use Disorders such as Substance Dependence, Substance Craving and Substance Abuse; Substance-induced Disorders such as Substance Intoxication, Substance Withdrawal, Substance-induced Delirium, Substance-Induced Persisting Dementia, Substance-induced Persisting Amnestic Disorder, Substance-Induced Psychotic Disorder, Substance-Induced Mood Disorder, Substance-induced Anxiety Disorder, Substance-Induced Sexual Dysfunction, Substance-induced Sleep Disorder and Hallucinogen Persisting Perception Disorder (Flashbacks); Alcohol-Related Disorders such as Alcohol Dependence (303.90), Alcohol Abuse (305.00), Alcohol Intoxication (303.00), Alcohol Withdrawal (291.81), Alcohol Intoxication Delirium, Alcohol Withdrawal Delirium, Alcohol-Induced Persisting Dementia, Alcohol-Induced Persisting Amnestic Disorder, Alcohol-Induced Psychotic Disorder, Alcohol-induced Mood Disorder, Alcohol-Induced Anxiety Disorder, Alcohol-induced Sexual Dysfunction, Alcohol-Induced Sleep Disorder and Alcohol-Related Disorder Not Otherwise Specified (291.9); Amphetamine (or Amphetamine-Like)-Related Disorders such as Amphetamine Dependence (304.40), Amphetamine Abuse (305.70), Amphetamine Intoxication (292.89), Amphetamine Withdrawal (292.0), Amphetamine Intoxication Delirium, Amphetamine Induced Psychotic Disorder, Amphetamine-Induced Mood Disorder, Amphetamine-Induced Anxiety Disorder, Amphetamine-Induced Sexual Dysfunction, Amphetamine-induced Sleep Disorder and Amphetamine-Related Disorder Not Otherwise Specified (292.9); Caffeine Related Disorders such as Caffeine Intoxication (305.90), Caffeine-induced Anxiety Disorder, Caffeine-Induced Sleep Disorder and Caffeine-Related Disorder Not Otherwise Specified (292.9); Cannabis-Related Disorders such as Cannabis Dependence (304.30), Cannabis Abuse (305.20), Cannabis Intoxication (292.89), Cannabis Intoxication Delirium, Cannabis-Induced Psychotic Disorder, Cannabis-Induced Anxiety Disorder and Cannabis-Related Disorder Not Otherwise Specified (292.9); Cocaine-Related Disorders such as Cocaine Dependence (304.20), Cocaine Abuse (305.60), Cocaine Intoxication (292.89), Cocaine Withdrawal (292.0), Cocaine Intoxication Delirium, Cocaine-Induced Psychotic Disorder, Cocaine-induced Mood Disorder, Cocaine-induced Anxiety Disorder, Cocaine-induced Sexual Dysfunction, Cocaine-Induced Sleep Disorder and Cocaine-Related Disorder Not Otherwise Specified (292.9); Hallucinogen-Related Disorders such as Hallucinogen Dependence (304.50), Hallucinogen Abuse (305.30), Hallucinogen Intoxication (292.89), Hallucinogen Persisting Perception Disorder (Flashbacks) (292.89), Hallucinogen Intoxication Delirium, Hallucinogen-induced Psychotic Disorder, Hallucinogen-induced Mood Disorder, Hallucinogen-induced Anxiety Disorder and Hallucinogen-Related Disorder Not Otherwise Specified (292.9); Inhalant-Related Disorders such as Inhalant Dependence (304.60), Inhalant Abuse (305.90), Inhalant Intoxication (292.89), Inhalant Intoxication Delirium, Inhalant-Induced Persisting Dementia, Inhalant-induced Psychotic Disorder, Inhalant-induced Mood Disorder, Inhalant-induced Anxiety Disorder and Inhalant-Related Disorder Not Otherwise Specified (292.9); Nicotine-Related Disorders such as Nicotine Dependence (305.1), Nicotine Withdrawal (292.0) and Nicotine-Related Disorder Not Otherwise Specified (292.9); Opioid-Related Disorders such as Opioid Dependence (304.00), Opioid Abuse (305.50), Opioid Intoxication (292.89), Opioid Withdrawal (292.0), Opioid Intoxication Delirium, Opioid-Induced Psychotic Disorder, Opioid-Induced Mood Disorder, Opioid-Induced Sexual Dysfunction, Opioid-Induced Sleep Disorder and Opioid-Related Disorder Not Otherwise Specified (292.9); Phencyclidine (or Phencyclidine-Like)-Related Disorders such as Phencyclidine Dependence (304.60), Phencyclidine Abuse (305.90), Phencyclidine Intoxication (292.89), Phencyclidine Intoxication Delirium, Phencyclidine-Induced Psychotic Disorder, Phencyclidine-Induced Mood Disorder, Phencyclidine-Induced Anxiety Disorder and Phencyclidine-Related Disorder Not Otherwise Specified (292.9); Sedative-, Hypnotic-, or Anxiolytic-Related Disorders such as Sedative, Hypnotic, or Anxiolytic Dependence (304.10), Sedative, Hypnotic, or Anxiolytic Abuse (305.40), Sedative, Hypnotic, or Anxiolytic Intoxication (292.89), Sedative, Hypnotic, or Anxiolytic Withdrawal (292.0), Sedative, Hypnotic, or Anxiolytic Intoxication Delirium, Sedative, Hypnotic, or Anxiolytic Withdrawal Delirium, Sedative-, Hypnotic-, or Anxiolytic-Persisting Dementia, Sedative-, Hypnotic-, or Anxiolytic-Persisting Amnestic Disorder, Sedative-, Hypnotic-, or Anxiolytic-Induced Psychotic Disorder, Sedative-, Hypnotic-, or Anxiolytic-Induced Mood Disorder, Sedative-, Hypnotic-, or Anxiolytic-Induced Anxiety Disorder Sedative-, Hypnotic-, or Anxiolytic-Induced Sexual Dysfunction, Sedative-, Hypnotic-, or Anxiolytic-Induced Sleep Disorder and Sedative-, Hypnotic-, or Anxiolytic-Related Disorder Not Otherwise Specified (292.9); Polysubstance-Related Disorder such as Polysubstance Dependence (304.80); and Other (or Unknown) Substance-Related Disorders such as Anabolic Steroids, Nitrate Inhalants and Nitrous Oxide: 
     Sleep disorders including primary sleep disorders such as Dyssomnias such as Primary Insomnia (307.42), Primary Hypersomnia (307.44), Narcolepsy (347), Breathing-Related Sleep Disorders (780.59), Circadian Rhythm Sleep Disorder (307.45) and Dyssomnia Not Otherwise Specified (307.47); primary sleep disorders such as Parasomnias such as Nightmare Disorder (307.47), Sleep Terror Disorder (307.46), Sleepwalking Disorder (307.46) and Parasomnia Not Otherwise Specified (307.47); Sleep Disorders Related to Another Mental Disorder such as Insomnia Related to Another Mental Disorder (307.42) and Hypersomnia Related to Another Mental Disorder (307.44); Sleep Disorder Due to a General Medical Condition, in particular sleep disturbances associated with such diseases as neurological disorders, neuropathic pain, restless leg syndrome, heart and lung diseases; and Substance-Induced Sleep Disorder including the subtypes Insomnia Type, Hypersomnia Type, Parasomnia Type and Mixed Type; sleep apnea and jet-lag syndrome: 
     Autism Spectrum Disorders including Autistic Disorder (299.00), Asperger&#39;s Disorder (299.80), Rett&#39;s Disorder (299.80), Childhood Disintegrative Disorder (299.10) and Pervasive Disorder Not Otherwise Specified (299.80, including Atypical Autism). 
     Attention-Deficit/Hyperactivity Disorder including the subtypes Attention-Deficit/Hyperactivity Disorder Combined Type (314.01), Attention-Deficit/Hyperactivity Disorder Predominantly Inattentive Type (314.00), Attention-Deficit/Hyperactivity Disorder Hyperactive-impulse Type (314.01) and Attention-Deficit/Hyperactivity Disorder Not Otherwise Specified (314.9); Hyperkinetic Disorder; Disruptive Behaviour Disorders such as Conduct Disorder including the subtypes childhood-onset type (321.81), Adolescent-Onset Type (312.82) and Unspecified Onset (312.89), Oppositional Defiant Disorder (313.81) and Disruptive Behaviour Disorder Not Otherwise Specified; and Tic Disorders such as Tourette&#39;s Disorder (307.23): 
     Personality Disorders including the subtypes Paranoid Personality Disorder (301.0), Schizoid Personality Disorder (301.20), Schizotypal Personality Disorder (301,22), Antisocial Personality Disorder (301.7), Borderline Personality Disorder (301,83), Histrionic Personality Disorder (301.50), Narcissistic Personality Disorder (301,81), Avoidant Personality Disorder (301.82), Dependent Personality Disorder (301.6), Obsessive-Compulsive Personality Disorder (301.4) and Personality Disorder Not Otherwise Specified (301.9): 
     Enhancement of cognition including the treatment of cognition impairment in other diseases such as schizophrenia, bipolar disorder, depression, other psychiatric disorders and psychotic conditions associated with cognitive impairment, e.g. Alzheimer&#39;s disease: and 
     Sexual dysfunctions including Sexual Desire Disorders such as Hypoactive Sexual Desire Disorder (302.71), and Sexual Aversion Disorder (302.79); sexual arousal disorders such as Female Sexual Arousal Disorder (302.72) and Male Erectile Disorder (302.72); orgasmic disorders such as Female Orgasmic Disorder (302.73), Male Orgasmic Disorder (302.74) and Premature Ejaculation (302.75); sexual pain disorder such as Dyspareunia (302.76) and Vaginismus (306.51); Sexual Dysfunction Not Otherwise Specified (302.70); paraphilias such as Exhibitionism (302.4), Fetishism (302.81), Frotteurism (302.89), Pedophilia (302.2), Sexual Masochism (302.83), Sexual Sadism (302.84), Transvestic Fetishism (302.3), Voyeurism (302.82) and Paraphilia Not Otherwise Specified (302.9); gender identity disorders such as Gender Identity Disorder in Children (302.6) and Gender Identity Disorder in Adolescents or Adults (302.85); and Sexual Disorder Not Otherwise Specified (302.9). 
     All of the various forms and sub-forms of the disorders mentioned herein are contemplated as part of the present invention. 
     Within the context of the present invention, the term “cognitive impairment” includes for example the treatment of impairment of cognitive functions including attention, orientation, learning disorders, memory (i.e. memory disorders, amnesia, amnesic disorders, transient global amnesia syndrome and age-associated memory impairment) and language function; cognitive impairment as a result of stroke, Alzheimer&#39;s disease, Huntington&#39;s disease, Pick disease, Aids-related dementia or other dementia states such as Multiinfarct dementia, alcoholic dementia, hypotiroidism-related dementia, and dementia associated to other degenerative disorders such as cerebellar atrophy and amyotropic lateral sclerosis; other acute or sub-acute conditions that may cause cognitive decline such as delirium or depression (pseudodementia states) trauma, head trauma, age related cognitive decline, stroke, neurodegeneration, drug-induced states, neurotoxic agents, mild cognitive impairment, age related cognitive impairment, autism related cognitive impairment, Down&#39;s syndrome, cognitive deficit related to psychosis, and post-electroconvulsive treatment related cognitive disorders; and dyskinetic disorders such as Parkinson&#39;s disease, neuroleptic-induced parkinsonism, and tardive dyskinesias. 
     The compounds of the invention may be administered in conventional dosage forms prepared by combining a compound of the invention with standard pharmaceutical carriers, diluents or excipients according to conventional procedures well known in the art. These procedures may involve mixing, granulating and compressing or dissolving the ingredients as appropriate to the desired preparation. 
     The pharmaceutical compositions of the invention may be formulated for administration by any route, and include those in a form adapted for oral, topical or parenteral administration to mammals including humans. 
     The compositions may be formulated for administration by any route. The compositions may be in the form of tablets, capsules, powders, granules, lozenges, creams or liquid preparations, such as oral or sterile parenteral solutions or suspensions. 
     The topical formulations of the present invention may be presented as, for instance, ointments, creams or lotions, eye ointments and eye or ear drops, impregnated dressings and aerosols, and may contain appropriate conventional additives such as preservatives, solvents to assist drug penetration and emollients in ointments and creams. 
     The formulations may also contain compatible conventional carriers, such as cream or ointment bases and ethanol or oleyl alcohol for lotions. Such carriers may be present as from about 1% up to about 98% of the formulation. More usually they will form up to about 80% of the formulation. 
     Tablets and capsules for oral administration may be in unit dose presentation form, and may contain conventional excipients such as binding agents, for example syrup, acacia, gelatin, sorbitol, tragacanth, or polyvinylpyrrolidone; fillers, for example lactose, sugar, maize-starch, calcium phosphate, sorbitol or glycine; tabletting lubricants, for example magnesium stearate, talc, polyethylene glycol or silica; disintegrants, for example potato starch; or acceptable wetting agents such as sodium lauryl sulphate. The tablets may be coated according to methods well known in normal pharmaceutical practice. Oral liquid preparations may be in the form of, for example, aqueous or oily suspensions, solutions, emulsions, syrups or elixirs, or may be presented as a dry product for reconstitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives, such as suspending agents, for example sorbitol, methyl cellulose, glucose syrup, gelatin, hydroxyethyl cellulose, carboxymethyl cellulose, aluminium stearate gel or hydrogenated edible fats, emulsifying agents, for example lecithin, sorbitan monooleate, or acacia; non-aqueous vehicles (which may include edible oils), for example almond oil, oily esters such as glycerine, propylene glycol, or ethyl alcohol; preservatives, for example methyl or propyl p-hydroxybenzoate or sorbic acid, and, if desired, conventional flavouring or colouring agents. 
     Suppositories will contain conventional suppository bases, e.g. cocoa-butter or other glyceride. 
     For parenteral administration, fluid unit dosage forms are prepared utilising the compound and a sterile vehicle, for example water. The compound, depending on the vehicle and concentration used, can be either suspended or dissolved in the vehicle. In preparing solutions the compound can be dissolved in water for injection and filter sterilised before filling into a suitable vial or ampoule and sealing. 
     Agents such as a local anaesthetic, preservative and buffering agents may also be dissolved in the vehicle. To enhance the stability, the composition can be frozen after filling into the vial and the water removed under vacuum. The dry lyophilised powder is then sealed in the vial and an accompanying vial of water for injection may be supplied to reconstitute the liquid prior to use. Parenteral suspensions are prepared in substantially the same manner except that the compound is suspended in the vehicle instead of being dissolved and sterilisation cannot be accomplished by filtration. The compound can be sterilised by exposure to ethylene oxide before suspending in the sterile vehicle. A surfactant or wetting agent may also be included in the composition to facilitate uniform distribution of the compound. 
     The compositions of the present invention may contain from 0.1% by weight, for example from 10-60% by weight, of the active material, depending on the method of administration. Where the compositions comprise dosage units, each unit may, for example contain from 0.1 to 20 mg of the active ingredient. For example, such a unit may contain from 1 to 10 mg. The dosage as employed for adult human treatment may, for example, range from 2 to 50 mg per day, for instance 5 to 20 mg per day depending on the route and frequency of administration (though in some instances, a dosage of 50 mg to 100 mg per day may be appropriate). Based on a 75 kg individual, such a dosage corresponds to 0.027 to 0.667 mg/kg per day. Suitably the dosage is from 0.05 to 0.3 mg/kg per day. 
     It will be recognised by one of skill in the art that the optimal quantity and spacing of individual dosages of a compound of the invention will be determined by the nature and extent of the condition being treated, the form, route and site of administration, and the particular mammal being treated, and that such optimums can be determined by conventional techniques. It will also be appreciated by one of skill in the art that the optimal course of treatment, i.e. the number of doses of a compound of the invention given per day for a defined number of days, can be ascertained by those skilled in the art using conventional course of treatment determination tests. 
     The compounds of the invention may be used in combination with one or more of the following agents to treat psychotic disorders: i) antipsychotics (such as olanzapine, risperidone, clozapine, ziprazidone, talnetant); ii) drugs for extrapyramidal side effects, for example anticholinergics (such as benztropine, biperiden, procyclidine, trihexyphenidyl), antihistamines (such as diphenhydramine), dopaminergics (such as amantadine); iii) antidepressants; iv) anxiolytics; v) cognitive enhancers for example cholinesterase inhibitors (such as tacrine, donepezil, rivastigmine, galantamine). 
     The compounds of the invention may be used in combination with antidepressants to treat depression and mood disorders. 
     The compounds of the invention may be used in combination with one or more of the following agents to treat bipolar disease: i) mood stabilisers; ii) antipsychotics; iii) antidepressants. 
     The compounds of the invention may be used in combination with one or more of the following agents to treat anxiety disorders: i) anxiolytics; ii) antidepressants. 
     The compounds of the invention may be used in combination with one or more of the following agents to improve nicotine withdrawal and reduce nicotine craving: i) nicotine replacement therapy, for example a sublingual formulation of nicotine beta-cyclodextrin and nicotine patches; ii) drugs for treating nicotine addition, for example bupropion. 
     The compounds of the invention may be used in combination with one or more of the following agents to improve alcohol withdrawal and reduce alcohol craving: i) NMDA receptor antagonists for example acamprosate; ii) GABA receptor agonists for example tetrabamate; iii) Opioid receptor antagonists for example naltrexone. 
     The compounds of the invention may be used in combination with one or more of the following agents to improve opiate withdrawal and reduce opiate craving: i) opioid mu receptor agonist/opioid kappa receptor antagonist for example buprenorphine; ii) opioid receptor antagonists for example naltrexone; iii) vasodilatory antihypertensives for example lofexidine. 
     The compounds of the invention may be used in combination with one or more of the following agents to treat sleeping disorders: i) benzodiazepines for example temazepam, lormetazepam, estazolam, triazolam; ii) non-benzodiazepine hypnotics for example zolpidem, zopiclone, zaleplon, indiplon; iii) barbiturates for example aprobarbital, butabarbital, pentobarbital, secobarbita, phenobarbital; iv) antidepressants; v) other sedative-hypnotics for example chloral hydrate, chlormethiazole. 
     The compounds of the invention may be used in combination with one or more of the following agents to treat anorexia: i) appetite stimulants for example cyproheptidine; ii) antidepressants; iii) antipsychotics; iv) zinc; v) premenstrual agents for example pyridoxine and progesterones. 
     The compounds of the invention may be used in combination with one or more of the following agents to treat bulimia: i) antidepressants; ii) opioid receptor antagonists; iii) antiemetics for example ondansetron; iv) testosterone receptor antagonists for example flutamide; v) mood stabilisers; vi) zinc; vii) premenstrual agents. 
     The compounds of the invention may be used in combination with one or more of the following agents to treat autism: i) antipsychotics; ii) antidepressants; iii) anxiolytics; iv) stimulants for example methylphenidate, amphetamine formulations, pemoline. 
     The compounds of the invention may be used in combination with one or more of the following agents to treat Attention Deficit Hyperactivity Disorder: i) stimulants for example methylphenidate, amphetamine formulations, pemoline; ii) non-stimulants for example norepinephrine reuptake inhibitors (such as atomoxetine), alpha 2 adrenoceptor agonists (such as clonidine), antidepressants, modafinil, cholinesterase inhibitors (such as galantamine and donezepil). 
     The compounds of the invention may be used in combination with one or more of the following agents to treat personality disorders: i) antipsychotics; ii) antidepressants; iii) mood stabilisers; iv) anxiolytics. 
     The compounds of the invention may be used in combination with one or more of the following agents to treat male sexual dysfunction: i) phosphodiesterase V inhibitors, for example vardenafil, sildenafil; ii) dopamine agonists/dopamine transport inhibitors for example apomorphine, buproprion; iii) alpha adrenoceptor antagonists for example phentolamine; iv) prostaglandin agonists for example alprostadil; v) testosterone agonists such as testosterone; vi) serotonin transport inhibitors for example serotonin reuptake inhibitors; v) noradrenaline transport inhibitors for example reboxetine; vii) 5-HT1A agonists, for example flibanserine. 
     The compounds of the invention may be used in combination with one or more of the following agents to treat female sexual dysfunction: i) the same agents specified for male sexual dysfunction, ii) an estrogen agonist such as estradiol. 
     Antipsychotic drugs include Typical Antipsychotics (for example chlorpromazine, thioridazine, mesoridazine, fluphenazine, perphenazine, prochlorperazine, trifluoperazine, thiothixine, haloperidol, molindone and loxapine); and Atypical Antipsychotics (for example clozapine, olanzapine, risperidone, quetiapine, aripirazole, ziprasidone, amisulpride, ziprazidone and talnetant). 
     Antidepressant drugs include serotonin reuptake inhibitors (such as citalopram, escitalopram, fluoxetine, paroxetine and sertraline); dual serotonin/noradrenaline reuptake inhibitors (such as venlafaxine, duloxetine and milnacipran); Noradrenaline reuptake inhibitors (such as reboxetine); tricyclic antidepressants (such as amitriptyline, clomipramine, imipramine, maprotiline, nortriptyline and trimipramine); monoamine oxidase inhibitors (such as isocarboxazide, moclobemide, phenelzine and tranylcypromine); and others (such as bupropion, mianserin, mirtazapine, nefazodone and trazodone). 
     Mood stabiliser drugs include lithium, sodium valproate/valproic acid/divalproex, carbamazepine, lamotrigine, gabapentin, topiramate and tiagabine. 
     Anxiolytics include benzodiazepines such as alprazolam and lorazepam. 
     It is to be understood that “treatment” as used herein includes prophylaxis as well as alleviation of established symptoms. 
    
    
     EXAMPLES 
     The invention is illustrated by the Examples described below. 
     Starting materials were obtained from commercial suppliers and used without further purification unless otherwise stated. Flash chromatography was carried out using pre-packed Isolute Flash™ or Biotage™ silica-gel columns as the stationary phase and analytical grade solvents as the eluent. 
     NMR spectra were obtained at 298K, at the frequency stated using either a Bruker™ DPX400 or an Oxford Instruments™ 250 MHz machine and run as a dilute solution of CDCl 3  unless otherwise stated. All NMR spectra were reference to tetramethylsilane (TMS δ H  0, δ C  0). All coupling constants are reported in hertz (Hz), and multiplicities are labelled s (singlet), bs, (broad singlet), d (doublet), t (triplet), q (quartet), dd (doublet of doublets), dt (doublet of triplets) and m (multiplet). 
     Total ion current traces were obtained for electrospray positive and negative ionisation (ES+/ES−) and atmospheric pressure chemical positive and negative ionisation (AP+/AP−). 
     In the procedures that follow, reference to an Intermediate or Example by number is typically provided. This is provided merely for assistance to the skilled chemist to identify the starting material used. The starting material may not necessarily have been prepared from the batch referred to. 
     
       
         
         
             
             
         
       
     
     Intermediate 1: trans-4-Phenyltetrahydro-3-furanol 
     
       
         
         
             
             
         
       
     
     Copper iodide (1.26 g, 6.61 mmol), phenyl magnesium bromide (3M in Et 2 O, 31.5 ml, 94.49 mmol) and dry tetrahydrofuran (10 ml) were placed in a flask under nitrogen atmosphere. The mixture was cooled to 0° C. and a solution of 3,6-dioxabicyclo[3.1.0]hexane (8.13 g, 94.49 mmol) in tetrahydrofuran (20 ml) was added dropwise. The reaction was stirred for 3 hours, diluted with saturated solution of NH 4 Cl and then extracted with ethyl acetate and dichloromethane. The combined organic phases were dried over sodium sulphate and concentrated to dryness to give the title compound (16.32 g) as crude material. 
     Intermediate 2: 4-phenyldihydro-3(2H)-furanone 
     
       
         
         
             
             
         
       
     
     To a stirred solution of (3R,4S)-rel-4-phenyltetrahydro-3-furanol (Intermediate 1) (5.09 g, 0.031 mol) in dichloromethane (125 ml) cooled to 0° C. trichloroisocyanuric acid (90%, 8.4 g, 0.033 mol) was added followed by the addition of TEMPO (2,2,6,6,-tetramethyl-1-piperidinyloxy) (0.052 g, 0.340 mmol). After the addition, the reaction was warmed to room temperature and stirred for 3 h monitoring the reaction by TLC (hexane/ethyl acetate 8/2). The reaction mixture was filtered on Celite. The organic phase was washed with a saturated NaHCO 3  solution, then with 1N HCl and brine. The organic layer was dried on magnesium sulphate and then evaporated under reduced pressure to give the title compound (4.1 g). 
     Intermediate 3: cis-4-Phenyl-N-(phenylmethyl)tetrahydro-3-furanamine 
     
       
         
         
             
             
         
       
     
     4-phenyldihydro-3(2H)-furanone (Intermediate 2) (1 g, 6.2 mmol) was dissolved in dry dichloromethane (25 ml) then benzylamine (0.874 ml, 8.0 mmol) was added dropwise. After stirring for 40 min, acetic acid (0.450 ml, 8.0 mmol) and sodium triacetoxyborohydride were added sequentially to the reaction mixture. After 18 hours the reaction was diluted with water, organic layer was separated, dried over sodium sulphate and concentrated under vacuo. The crude material was purified by SiO 2  flash chromatography eluting with ethyl acetate/hexane 30/70. Evaporation of the solvent afforded 1.2 g of title material. 
     Intermediate 4: [cis-4-phenyltetrahydro-3-furanyl]amine 
     
       
         
         
             
             
         
       
     
     To a solution of cis-4-Phenyl-N-(phenylmethyl)tetrahydro-3-furanamine (intermediate 3) (3.74 g, 15 mmol) in methanol (70 ml) Pd(OH) 2 /C (20% w/w, 1.36 g) was added. The reaction vessel was charged with H 2  (50 atm) and the mixture reacted overnight. The reaction mixture was filtered on Celite and concentrated to dryness to afford the title material (2.35 g). 
     Intermediate 5: [cis-4-(4-iodophenyl)tetrahydro-3-furanyl]amine 
     
       
         
         
             
             
         
       
     
     To a solution of [cis-4-phenyltetrahydro-3-furanyl]amine (intermediate 4) (5.47 g, 33.5 mmoli) in acetonitrile (40 ml) cooled to 0° C. trifluoromethansulfonic acid (8.3 ml, 93.8 mmoli) and NIS (6.8 g, 30 mmoli) were sequentially added. The reaction mixture was stirred at room temperature for 18 hours, then a saturated NaHCO 3  solution and dichloromethane were added. The organic phase was separated and the aqueous layer extracted again with ethyl acetate. The combined organic phases were dried over sodium sulphate and concentrated under vacuo. The crude material was purified by SiO 2  flash chromatography eluting with dichloromethane/methanol 19.6/1. Evaporation of the solvent afforded 5 g of title material. 
     Intermediate 6: N-[cis-(4-iodophenyl)tetrahydro-3-furanyl]-2-propanesulfonamide 
     
       
         
         
             
             
         
       
     
     To a solution of [cis-4-(4-iodophenyl)tetrahydro-3-furanyl]amine (3.2 g, 11 mmol) in anhydrous dichloromethane (80 ml) cooled to 0° C., DBU (3.47 ml, 2.32 mmol) was first added and then isopropylsulfonyl chloride (2.59 ml, 2.32 mmol) was added dropwise. The reaction mixture was stirred for 2 hours following the reaction by TLC (dichloromethane/methanol 19.6/1). The reaction mixture was diluted with dichloromethane and then a saturated NH 4 Cl solution was added. The organic layer was separated and washed with brine. The organic layers were separated, dried over magnesium sulphate and evaporated under reduced pressure. The crude material was purified by SiO 2  flash chromatography eluting with ethyl acetate/hexane 1/1 to give the title compound (3.1 g) as a white solid. 
     NMR (CDCl 3 ): 7.66 (d, 2H), 7.09 (d, 2H), 7.06 (d, 1H), 4.18 (m, 1H), 4.04 (m, 2H), 3.94 (t, 1H), 3.62 (dd, 1H), 3.44 (m, 1H), 2.86 (m, 1H), 1.04 (d, 3H), 0.91 (d, 3H). The cis arrangement of the PhI and NHSO 2 iPr groups was confirmed by an NMR NOE experiment 
     Intermediate 7: N-{cis-4-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]tetrahydro-3-furanyl}-2-propanesulfonamide 
     
       
         
         
             
             
         
       
     
     A mixture of potassium acetate (989 mg, 10.08 mmol), [1,1′-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) complex with dichloromethane (137 mg, 0.168 mmol) and Bis(pinacolato)diboron (1.02 g, 4.03 mmol) were flushed with nitrogen and a solution of N-[cis-4-(4-iodophenyl)tetrahydro-3-furanyl]-2-propanesulfonamide (Intermediate 7) (1.33 g, 3.36 mmol) in dry dimethylsulphoxide (20 ml) was added. The reaction mixture was stirred at 80° C. for 3 h, then it was allowed to cool to room temperature, filtered on Celite pad, washed with ethyl acetate and concentrated in vacuo to give a residue which was taken up into ethyl acetate and washed with water. The aqueous phase was extracted with ethyl acetate and the combined organic layers were dried over sodium sulphate and concentrated in vacuo to obtain a brown oil which was purified by flash-chromatography (Horizon instrument, 40M+ cartridge, eluent cyclohexane-ethyl acetate 7:3) to give the title compound as a yellowish solid (976 mg, 74%) 
     Examples 1 to 12 
     
       
         
         
             
             
         
       
     
     In 8 ml vials (PLS apparatus) the bromoaryl reagent (0.349 mmol) was placed together with a solution of N-{(3S,4R)-4-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]tetrahydro-3-furanyl}-2-propanesulfonamide (Intermediate 7) (69 mg, 0.174 mmol) in dry 1, 4-dioxane (1.0 ml), Polymer supported Tetrakis catalyst (PoI—Pd(PPh 3 ) 4 ) (47 mg, 0.00516 mmol), Na 2 CO 3  2M (0.215 ml, 0.43 mmol) were added. The reaction mixture was shaken at 90° C. for 3 h, then monitored by LC/MS, shaken at 90° C. for a further 45 minutes and then left shaking at room temperature overnight. The resin was filtered off (by Alltech filter tube) and washed with dichloromethane (1 ml), methanol (1 ml), water (1 ml) and dichloromethane (1 ml). The liquid phase was concentrated in vacuo. The residue was taken into dichloromethane (2 ml) and washed with water (0.5 ml) and the phases were separated using Alltech phase separator tube. The aqueous phase was extracted with dichloromethane (2×1 ml) and the organic phase was concentrated under nitrogen atmosphere. The crude oil which was purified by reverse phase HPLC to give the title compound. The HPLC conditions were as given in “Preparative Chromatography” below. 
     Examples 1 to 12 as synthesised by this route are summarised in Table 1. The compounds were synthesised as racemates. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                 HPLC rt 
                   
                 Yield 
               
               
                 Ex 
                 structure 
                 Name 
                 (min) 
                 MS 
                 (%) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 1 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-{cis-4-[4-(6-fluoro-3- pyridinyl)phenyl]tetra- hydro-3-furanyl}-2- propanesulfonamide 
                 2.09 
                 365 [MH] +   
                 46 
               
               
                   
               
               
                 2 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-{cis-4-[4-(6-methyl- 3- pyridinyl)phenyl]tetra- hydro-3-furanyl}-2- propanesulfonamide 
                 1.41 
                 361 [MH] +   
                 27 
               
               
                   
               
               
                 3 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-{cis-4-[4-(5-fluoro-2- pyridinyl)phenyl]tetra- hydro-3-furanyl}-2- propanesulfonamide 
                 2.07 
                 365 [MH] +   
                 32 
               
               
                   
               
               
                 4 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-{cis-4-[4-(5-fluoro-3- pyridinyl)phenyl]tetra- hydro-3-furanyl}-2- propanesulfonamide 
                 1.64 
                 365 [MH] +   
                 60 
               
               
                   
               
               
                 5 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-{cis-4-[4-(5-chloro- 2- pyridinyl)phenyl]tetra- hydro-3-furanyl}-2- propanesulfonamide 
                 2.62 
                 381 [MH] +   
                 34 
               
               
                   
               
               
                 6 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-{cis-4-[4-(5-methyl- 3- pyridinyl)phenyl]tetra- hydro-3-furanyl}-2- propanesulfonamide 
                 2 
                 361 [MH] +   
                 10 
               
               
                   
               
               
                 7 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-[cis-4-(4′-fluoro-4- biphenylyl)tetrahydro- 3-furanyl]-2- propanesulfonamide 
                 3.06 
                 364 [MH] +   
                 18 
               
               
                   
               
               
                 8 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-[cis-4-(4′-cyano-4- biphenylyl)tetrahydro- 3-furanyl]-2- propanesulfonamide 
                 2.59 
                 371 [MH] +   
                 45 
               
               
                   
               
               
                 9 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-[cis-4-(3′-acetyl-4- biphenylyl)tetrahydro- 3-furanyl]-2- propanesulfonamide 
                 2.46 
                 388 [MH] +   
                 32 
               
               
                   
               
               
                 10 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-{cis-4-[4-(1,3- benzodioxol-5- yl)phenyl]tetrahydro- 3-furanyl}-2- propanesulfonamide 
                 2.82 
                 390 [MH] +   
                 27 
               
               
                   
               
               
                 11 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-{cis-4-[4-(3- thienyl)phenyl]tetra- hydro-3-furanyl}-2- propanesulfonamide 
                 2.75 
                 352 [MH] +   
                 26 
               
               
                   
               
               
                 12 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 N-{cis-4-[4-(2- thienyl)phenyl]tetra- hydro-3-furanyl}-2- propanesulfonamide 
                 2.85 
                 352 [MH] +   
                 82 
               
               
                   
               
            
           
         
       
     
     Examples 2, 7, 9 and 12 were analysed by  1 H-NMR, giving the following spectral data: 
     Example 2 
       1 H-NMR (400 MHz, CDCl 3 ): 1.21 (3H, d), 1.27 (3H, d), 2.63 (3H, s), 3.01 (1H, m), 3.66 (2H, m), 3.74 (1H, dd), 4.18 (1H, dd), 4.25 (2H, m), 4.40 (1H, m), 7.26 (1H, d), 7.42 (2H, d), 7.60 (2H, d), 7.79 (1H, dd), 8.73 (1H, s). 
     Example 7 
       1 H-NMR (400 MHz, CDCl 3 ): 0.86 (3H, d), 1.01 (3H, d), 2.83 (1H, m), 3.53 (1H, m), 3.68 (1H, dd), 4.04 (1H, m), 4.08 (2H, m), 4.22 (1H, m), 7.12 (1H, d), 7.27 (2H, t), 7.38 (2H, d), 7.60 (2H, d), 7.69 (2H, dd). 
     Example 9 
       1 H-NMR (400 MHz, CDCl 3 ): 0.88 (3H, d), 1.02 (3H, d), 2.65 (3H, s), 2.85 (1H, m), 3.55 (1H, m), 3.69 (1H, dd), 4.07 (3H, m), 4.24 (1H, m), 7.13 (1H, d), 7.43 (2H, d), 7.61 (1H, t), 7.70 (2H, d), 7.93 (2H, d), 8.17 (1H, m). 
     Example 12 
       1 H-NMR (400 MHz, CDCl 3 ): 0.89 (3H, d), 1.02 (3H, d), 2.85 (1H, m), 3.50 (1H, m), 3.66 (1H, dd), 4.02 (1H, t), 4.06 (2H, m), 4.21 (1H, s broad), 7.10 (1H, m), 7.12 (1H, dd), 7.33 (2H, d), 7.49 (1H, d), 7.51 (1H, dd), 7.60 (2H, d). 
     The chromatography conditions used were as follows: 
     
       
         
           
               
             
               
                   
               
             
            
               
                 Analytical HPLC conditions (used for analysis quoted in Table 1) 
               
            
           
           
               
               
            
               
                 Column 1: 
                 GEMINI C18 5 μm, 50 × 4.6 mm 
               
               
                 Mobile phase 
                 A: NH4HCO3 sol. 10 mM, pH10; B: CH 3 CN 
               
               
                 Gradient: 
                 35% (B) for 0.5 min, from 30% (B) to 
               
               
                   
                 95% (B) in 4.5 min, 95% (B) for 3 min 
               
               
                 Flow rate: 
                 2 ml/min 
               
               
                 UV wavelength range: 
                 210-350 nm 
               
               
                 Mass range: 
                 100-900 amu 
               
               
                 Ionization: 
                 ES+ 
               
            
           
           
               
            
               
                 Preparative HPLC chromatographic conditions 
               
            
           
           
               
               
            
               
                 Column: 
                 GEMINI C18 5 μm, 100 × 21 mm 
               
               
                 Mobile phase: 
                 A: NH4HCO3 sol. 10 mM, pH10; B: CH3CN 
               
               
                 Gradient 1*: 
                 30% (B) for 1 min, from 30% (B) to 
               
               
                   
                 95% (B) in 12 min, 95% (B) for 3 min 
               
               
                 Gradient 2**: 
                 10% (B) for 1 min, from 10% (B) to 
               
               
                   
                 95% (B) in 12 min, 95% (B) for 3 min 
               
               
                 Flow rate: 
                 17 ml/min 
               
               
                 UV wavelength range: 
                 210-350 nm 
               
               
                 Mass range: 
                 100-900 amu 
               
               
                 Ionization: 
                 ES+ 
               
               
                   
               
               
                 *used for Examples 3, 5, 7, 8, 9, 10, 11 
               
               
                 **used for Examples 1, 2, 4, 6 
               
            
           
         
       
     
     Biological Assays 
     The ability of the compounds of the invention to potentiate glutamate receptor-mediated response may be determined a) by using fluorescent calcium-indicator dyes such as FLUO4 and additionally b) by measuring glutamate-evoked current recorded from human GluR2 flip unedited HEK293 cells. 
     a) Calcium Influx Fluorescence Assay 
     384 well plates are prepared containing confluent monolayer of HEK 293 cells either stably expressing or transiently transfected with human GluR2 flip (unedited) AMPA receptor subunit. These cells form functional homotetrameric AMPA receptors. The tissue culture medium in the wells are discarded and the wells are each washed three times with standard buffer (80 μL) for the stable cell line (145 mM NaCl, 5 mM KCl, 1 mM MgCl 2 , 2 mM CaCl 2 , 20 mM N-[2-hydroxyethyl]-piperazine-N-[2-ethanesulfonic acid (HEPES), 5.5 mM glucose, pH 7.3) or with a Na-free buffer for the transient transfected cells (145 mM N-methyl-glucamine instead of NaCl). The plates are then incubated for 60 minutes in the dark with 2 μM FLUO4-AM dye (20 μL) (Molecular Probes, Netherlands) at room temperature to allow cell uptake of the FLUO-4AM, which is then converted to FLUO-4 by intracellular esterases which is unable to leave the cell. After incubation each well is washed three times with buffer (80 μL) (30 μL of buffer remained in each well after washing). 
     Compounds of the invention (or reference compounds such as cyclothiazide) are dissolved in dimethylsulfoxide (DMSO) at a stock concentration of 10 mM. These solutions are further diluted with DMSO using a Biomek FX (Beckman Coulter) in a 384 compound plate. Each dilution (1 μL) is transferred to another compound plate and buffer (50 μL) is added. An agonist stimulus (glutamate) plate is prepared by dissolving sodium glutamate in water to give a concentration of 100 mM. This solution is diluted with buffer to give a final concentration of 500 μM and dispensed into another 384-well plate (50 μL/well) using a Multidrop (Thermolabsystems). 
     The cell plate is then transferred into a fluorescence imaging plate based reader [such as the FLIPR384 (Molecular Devices)]. A baseline fluorescence reading is taken over a 10 to 240 second period, and then 10 μL from each plate containing a compound of the invention made up in standard buffer solution (in a concentration range from 100 μM to 10 μM) is added (to give a final concentration in the range 30 μM to 3 μM). The fluorescence is read over 5 minute period. 500 μM glutamate solution (10 μL) is added (to give a final concentration of 100 μM). The fluorescence is then read over a 4 minute period. The activities of the compounds of the invention and reference compounds are determined by measuring peak fluorescence after the last addition. The activity is also expressed relative to the fluorescence increase induced by cyclothiazide at their maximum response (i.e. greater than 30 μM). 
     The assay described above is believed to have an effective limit of detection of a pEC 50  in the region of 3.5-4.0 due to the limitations of compound solubility. The pEC 50  result is generally considered to be accurate +/−0.3. Accordingly, a compound exhibiting a pEC 50  value within this range from such an assay may indeed have a reasonable affinity for the receptor, but equally it may also have a lower affinity, including a considerably lower affinity. 
     The Example compounds were screened using the assay as described above and Examples 1 to 12 gave a pEC 50  equal to or greater than 4.0 and demonstrated an activity at least 50% that of cyclothiazide (at its maximal response). 
     b) Whole cell voltage-clamp electrophysiology Assay 
     The ability of the compounds of the invention to potentiate AMPA-subtype glutamate receptor-mediated response are determined by measuring AMPA-evoked current recorded from rat cultured hippocampal neurons. 
     This assay involves the electrophysiological characterisation of AMPA receptor positive modulators using rat cultured hippocampal neurons. The extracellular recording solution contains: 145 mM NaCl, 2.5 mM KCl, 1.2 mM MgCl 2 , 1.5 mM CaCl 2 , 10 mM N-[2-hydroxyethyl]-piperazine-N-[2-ethanesulfonic acid (HEPES), 10 mM D-glucose, pH 7.3 with NaOH. The intracellular solution contains: 80 mM CsCl, 80 mM CsF, 10 mM N-[2-hydroxyethyl]-piperazine-N-[2-ethanesulfonic acid (HEPES), 10 mM ethylene glycol-bis(g-aminoethylether)-N,N,N′,N,-tetra-acetic acid (EGTA), 14 mM MgATP, 14 mM DiTris Creatine Phosphate, 50 U/ml Creatine Phosphokinase pH 7.3 with CsOH. Recording electrodes are prepared from glass capillary tubes (Clark Electromedical GC120-F10) pulled into two equal lengths using a Zeitz Instruments DMZ Universal Puller, program 09, resulting in electrodes with a resistance of approximately 3-6 MOhms when measured in extracellular solution. Electrodes are back filled with internal recording solution. Positive pressure is applied to the electrode to prevent mixture of internal and external solutions and assist in formation of high resistance seal when the electrode makes contact with the cell membrane. Glass coverslip fragment, bearing rat cultured hippocampal neurons, is placed in the recording chamber positioned on the stage of an inverted microscope. A tube at the edge of the chamber is used to apply extracellular solution to the bath. Rapid solution exchange uses a fast step perfusion system (Biologic RSC160). Two outlet tubes attached together along their length are positioned close to a chosen cell so that the outflow from only one tube can pass directly over the cell surface. A motorized stepper could re-position the tubes such that the outflow from the second outlet tube flows over the cell allowing solution exchange at the cell membrane surface to occur within 10-20 ms. Excess bath solution is removed via a tube positioned at the edge of the chamber connected to a vacuum line. 
     A prospective cell is positioned in the centre of the microscope field of view. Recording electrode is positioned directly above the cell membrane surface. Using fine manipulator control (Luigs and Neumann, SM-6) the electrode is lowered, while monitoring the change in electrode resistance during delivery of a 5 mV depolarizing pulse, until a high resistance seal (gigaseal) is achieved. Whole cell configuration is achieved by removing by suction a small fragment of cell membrane immediately beneath the recording electrode tip. The cell membrane potential is held at −70 mV (voltage-clamped) via the electrode (Axopatch 200B Integrating patch clamp amplifier, pClamp software, Axon Instruments). Test solutions are applied using the fast application system using the following protocol and changes in inward current are recorded and stored for off-line analysis. 
     1) Control current−exchange from extracellular solution to extracellular solution+30 μM AMPA (2 s application time, 30 s interval between applications) repeated until measurements are stable.
 
2) Test current−exchange from extracellular solution+10 nM of compound of invention to extracellular solution+10 nM of compound of invention+30 μM AMPA (2 s application time, 30 s interval between applications) repeated until measurements are stable.
 
     All experiments are performed at ambient temperature (20 to 22° C.). 
     The activity of a compound of the invention is determined by measuring the area under the curve (during 2 s period of application) for the 30 μM AMPA response in the presence of the compound of the invention and expressing it as % of potentiation of the 30 μM AMPA alone response (30 μM AMPA in the absence of the compound of the invention).