WO1993013104A1 - C.n.s. active tricyclic thienopyridine derivatives - Google Patents

Abstract

Thienopyridinecarboxylic acid esters of formula (I), processes for their preparation and their use as pharmaceuticals.

Description

C.N. S. active tricycl ic thienopyridine derivatives

This invention relates to compounds having pharmacological activity, to a process for their preparation, to compositions containing them and to their use in the treatment of mammals.

I. Lalezari, Journal of Heterocyclic Chemistry, 16, 603, (1979) describes the preparation of 4-aminothieno[2,3-b]pyridine-5-carboxylate derivatives of formula (A):

wherein R_a is hydrogen or ethyl; R_b and R_c are methyl, or R_b and R_c together are -(CH₂)_n- where n is 3, 4 or 5.

No pharmacological activity is attributed to compounds of formula (A).

EP 0 327 223 discloses certain 5,6,7,8-tetrahydrobenzo[b]thieno[2,3-b] pyridine-3-carboxylic acid derivatives having CNS activity, in particular anxiolytic and/or antidepressant activity.

A class of compounds has now been discovered, which compounds have been found to have CNS activity, in particular anxiolytic and/or

anti-depressant and/or anticonvulsant activity and/or activity useful in the treatment of sleep disorders.

Accordingly, the present invention provides a compound of formula (I) or a pharmaceutically acceptable salt thereof:

wherein:

A is C_2-5 polymethylene optionally terminated or interrupted by oxygen, sulphur or NR₄ wherein R₄ is hydrogen, C_1-6 alkyl optionally substituted by hydroxy, C_1-7 alkanoyl, C_1-6 alkylsulphonyl, C_1-6 alkoxycarbonyl or C_2-6 alkenyloxycarbonyl, and wherein any methylene group is optionally substituted by R₅ where R₅ is selected from C_1-6 alkyl, C_1-6

alkoxycarbonyl, C_1-6 alkylthio, C_2-7 alkanoyl, trifluoromethyl, cyano, carbamoyl and carboxy, and phenyl or phenyl C_1-4 alkyl, in which any phenyl moiety in R₅ is optionally substituted by a group selected from C_1-6 alkyl, C_1-6 alkoxy, C_1-6 alkoxycarbonyl, C_1-6 alkylthio, hydroxy, C_2-7 alkanoyl, chloro, fluoro, trifluoromethyl, nitro, amino optionally substituted by one or two C_1-6 alkyl groups or by C_2-7 alkanoyl, cyano, carbamoyl and carboxy, with the proviso that A is not C₄ polymethylene optionally substituted by R₅;

R₁ is hydrogen, C_1-6 alkyl, phenyl or phenyl C_1-4 alkyl wherein the phenyl moiety is optionally substituted by one or more C_1-6 alkyl, C_1-6 alkoxy, C_1-6 alkylthio, hydroxy, C_2-7 alkanoyl, halo, trifluoromethyl, nitro, amino optionally substituted by one or two C_1-6 alkyl groups or by C_2-7 alkanoyl, cyano, carbamoyl or carboxy groups;

R₂ and R₃ are independently selected from hydrogen, C_1-6 alkyl, C_3-7 cycloalkyl, C_3-7 cycloalkyl- C_3-7 alkyl, C_3-6 alkenyl, C_1-7 alkanoyl, C_1-6 alkylsulphonyl, di-( C_1-6 alkyl)amino C_1-6 alkyl, 3-oxobutyl, 3-hydroxy- butyl, phenyl, phenyl C_1-6 alkyl, benzoyl, phenyl C_2-7 alkanoyl and benzenesulphonyl any of which phenyl moieties are optionally substituted by one or two halogen, C_1-6 alkyl, C_1-6 alkoxy, CF₃, amino or carboxy, or R₂ and R₃ together are C_2-7 polymethylene optionally interrupted by oxygen or NR₇ wherein R₇ is hydrogen or C_1-6 alkyl optionally

substituted by hydroxy; and -CO₂R₆ is a pharmaceutically acceptable ester group; for pharmaceutical use.

By pharmaceutical use is meant the treatment or prophylaxis of disorders in mammals including humans. Compounds of formula (I) and their pharmaceutically acceptable salts have anxiolytic and/or anti-depressant and/or anticonvulsant activity and/or activity useful in the treatment of sleep disorders and are of particular use in the treatment or prophylaxis of CNS disorders, in particular anxiety, depression, sleep disorders or diseases treatable with anticonvulsant agents such as epilepsy. Thus the invention also provides a compound of formula (I) or a pharmaceutically acceptable salt thereof, for use in the treatment or prophylaxis of CNS disorders, in particular anxiety, depression, sleep disorders or diseases treatable with anticonvulsant agents such as epilepsy.

The invention further provides a method of treatment or prophylaxis of CNS disorders, in particular anxiety, depression, sleep disorders or diseases treatable with anticonvulsant agents such as epilepsy in mammals including humans, which comprises administering to the sufferer an effective amount of a compound of formula (I) or a

pharmaceutically acceptable salt thereof.

In another aspect, the invention provides the use of a compound of formula (I) or a pharmaceutically acceptable salt thereof in the

preparation of a medicament for the treatment or prophylaxis of CNS disorders, in particular anxiety, depression, sleep disorders or diseases treatable with anticonvulsant agents such as epilepsy.

The present invention also provides a pharmaceutical composition, which comprises a compound of formula (I) or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

A pharmaceutical composition of the invention, which may be prepared by admixture, suitably at ambient temperature and atmospheric pressure, is usually adapted for oral or parenteral administration and, as such, may be in the form of tablets, capsules, oral liquid preparations, powders, granules, lozenges, reconstitutable powders, or injectable or infusable solutions or suspensions. Orally administrable compositions are generally preferred.

Tablets and capsules for oral ao!ministration may be in unit dose form, and may contain conventional exάpients, such as binding agents, fillers, tabletting lubricants, disintegrants and acceptable wetting agents. 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 suspension, solutions, emulsions, syrups or elixirs, or may be in the form of a dry product for reconstitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives such as suspending agents, emulsifying agents, non-aqueous vehicles (which may include edible oils), preservatives, and, if desired, conventional flavourings or colourants.

For parenteral administration, fluid unit dosage forms are prepared utilising a compound of the invention or pharmaceutically acceptable salt thereof and a sterile vehicle. 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 for injection and filter sterilised before filling into a suitable vial or ampoule and sealing. Advantageously, adjuvants such as a local anaesthetic, preservatives and buffering agents are dissolved in the vehicle. To enhance the stability, the composition can be frozen after filling into the vial and the water removed under vacuum. Parenteral suspensions are prepared in substantially the same manner, except that the compound is suspended in the vehicle instead of being dissolved, and sterilization cannot be accomplished by filtration. The compound can be sterilised by exposure to ethylene oxide before suspension in a sterile vehicle.

Advantageously, a surfactant or wetting agent is included in the composition to facilitate uniform distribution of the compound.

The composition may contain from 0.1% to 99% by weight, preferably from 10 to 60% by weight, of the active material, depending on the method of administration.

The dose of the compound used in the treatment of CNS disorders, such as anxiety, depression, sleep disorders or diseases treatable with

anticonvulsant agents such as epilepsy will vary in the usual way with the seriousness of the disorders, the weight of the sufferer, and other similar factors. However, as a general guide suitable unit doses may be 0.05 to 1000 mg, for anxiety more suitably 0.05 to 20.0 mg, for example 0.2 to 5 mg; and such unit doses may be administered more than once a day, for example two or three a day, so that, for anxiety, the total daily dosage is in the range of about 0.01 to 100 mg/kg; and such therapy may extend for a number of weeks or months.

Within the above indicated dosage range, no adverse toxicological effects are indicated with the compounds of the invention.

Alkyl moieties within the variables R₁ to R₅ and R₇ are preferably C_1-4 alkyl, such as methyl, ethyl and n- and iso-propvl.

It will be appreciated in selecting variables R₂ and R₃ that the nitrogen atom is not directly attached to unsaturated carbon. Values for A include -(CH₂)₃-, -(CH₂)₅-, -(CH₂)_n-O-(CH₂)_m-,

-(CH₂)_n-S-(CH₂)_m- and -(CH₂)_n-NR₄-(CH₂)_m- wherein n and m are independently zero or an integer of 1 to 4 such that (n+m) is an integer of 2 to 4, R₄ is hydrogen, C_1-4 alkyl, C_1-5 alkanoyl, C_1-4 alkylsulphonyl, C_1-4 alkoxycarbonyl or C_2-4 alkenyloxycarbonyl and any methylene group is optionally substituted by R₅ where R₅ is C_1-4 alkyl. Examples of R₄ include hydrogen, methyl, formyl, acetyl, propionyl, methoxycarbonyl, ethoxycarbonyl, t-butoxycarbonyl and vinyloxycarbonyl. Preferably any methylene group within A is unsubstituted and R₄ is formyl, acetyl or methoxycarbonyl.

Examples of A include -(CH₂)₃-, -(CH₂)₅-, -(CH₂)₂-O-CH₂-,

-(CH₂)₂-S-CH₂-, -(CH₂)₂-N(COCH₃)-CH₂-, -(CH₂)₂-NH-CH₂-,

-(CH₂)₂-NCH₃- CH₂-, -(CH₂)₂-N(CO₂CH₃)-CH₂-,

-(CH₂)₂-N(CO₂C₂H₅)-CH₂-, -(CH₂)₂-N(CHO)-CH₂-,

-(CH₂)₂-N(COC₂H₅)-CH₂-, -(CH₂)₂-N(SO₂CH₃)-CH₂ and

-(CH₂)₂-N(CO₂C(CH₃)₃)-CH₂-, wherein the ethylene moiety is attached to carbon atom 'a '; and -(CH₂)₃-N(CO₂C₂H₅)-, -(CH₂)₃-N(CO₂CH₃)- and -(CH₂)₃-N(CO₂CH=CH₂)- wherein the propylene moiety is attached to carbon atom 'a'.

Preferably A is -(CH₂)₃-, -(CH₂)₂-N(COCH₃)-CH₂- or

-(CH₂)₂-N(CO₂CH₃)-CH₂-.

Values for R₁ include hydrogen, methyl, ethyl, n- and iso-propyl, phenyl and benzyl. Preferably, R₁ is methyl.

Values for R₂ and R₃ include hydrogen, methyl, ethyl, n- and iso-propyl, n-, sec-, iso- and tert-butyl, n-, sec, iso- and neo-pentyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopentyl-C_1-4 alkyl, cyclohexyl-C_1-4 alkyl and cycloheptyl-C_1-4 alkyl, where values for C_1-4 alkyl include methylene and ethylene, but-2-enyl, but-3-enyl, 1-methylprop-2-enyl, formyl, acetyl, propionyl, methylsulphonyl, 3-dimethylaminobutyl, 3-oxobutyl,

3-hydroxybutyl, phenyl, benzyl, benzoyl, benzylcarbonyl and

benzenesulphonyl, or R₂ and R₃ together form -(CH ₂)_r-X-(CH₂)_s- wherein r and s are independently 1, 2 or 3 and X is a bond, O or NR₇, for example C₄ or C₅ polymethylene, -(CH₂)₂-O-(CH₂)₂- or -(CH₂)₂-NR₇-(CH₂)₂- where R₇ is preferably methyl.

Preferably R₂ is hydrogen and R₃ is hydrogen or C_1-6 alkyl, for example methyl. Most preferably R₂ and R₃ are hydrogen.

There is a preferred group of compounds within formula (I) of formula (II) or a pharmaceutically acceptable salt thereof:

wherein R₃ ¹ is hydrogen or C_1-6 alkyl and A, R₁ and R₆ are as defined in formula (I).

Preferred values for A, R₁ and R₃ ¹ are as described for the corresponding variables in formula (I).

The invention further provides novel compounds within formula (I), wherein the variable groups are as defined in formula (I) with the proviso that when A is -(CH₂)₃- or -(CH₂)₅-, R₁ is methyl and R₂ and R₃ are hydrogen, R₆ is other than ethyl. Such compounds are hereinafter referred to as compounds of formula (Ia).

The compounds of the formula (I) can form acid addition salts with acids, such as the conventional pharmaceutically acceptable acids, for example, maleic, hydrochloric, hydrobromic, phosphoric, acetic, fumaric, salicylic, citric, lactic, mandelic, tartaric and methanesulphonic.

Suitable examples of pharmaceutical esters of the compounds of formula (I) include C_1-6 alkyl esters wherein the alkyl moiety is optionally substituted by up to three halo atoms selected from chloro, fluoro and bromo, such as methyl, ethyl, n- and iso-propyl. n-, sec- and tert-butyl and 2,2,2-trifluoroethyl esters, C_2-6 alkenyl esters such as vinyl, prop-1-enyl, prop-2-enyl, 1-methylvinyl, but-1-enyl, but-2-enyl, but-3-enyl, pent-4-enyl, 1-methylenepropyl and 1-methylprop-2-enyl, (in both their E and Z forms where stereoisomerism exists), C_2-6 alkynyl esters such as prop-2-ynyl, but-2-ynyl, but-3-ynyl and pent 4-ynyl, C_3-6 cycloalkyl esters such as cyclohexyl and C_3-6 cycloalkyl-C_1-4 alkyl esters such as

cyclopropylmethyl, cyclopropylethyl and cyclobutylmethyl. Preferably the pharmaceutically acceptable ester is the methyl, ethyl, propyl,

prop-2-enyl, prop-2-ynyl or but-2-ynyl ester, i.e. R₆ is methyl, ethyl, propyl, prop-2-enyl, prop-2-ynyl or but-2-ynyl. Most preferably R₆ is ethyl or prop-2-ynyl.

It will be appreciated that the compounds of formula (I) in which R₂ or R₃ is hydrogen may exist tautomerically in more than one form. The invention extends to each of these forms and to mixtures thereof.

Compounds of formula (I) may also form solvates such as hydrates, and the invention also extends to these forms. When referred to herein, it is understood that the term "compound of formula (I)" also includes solvates thereof. The present invention also extends to any single stereoisomers such as enantiomers or diastereomers, or mixtures thereof including racemates, of compounds of formula (I).

A process for the preparation of a compound of formula (I), or a pharmaceutically acceptable salt thereof comprises the reaction of a compound of formula (III):

with a compound of formula (IV):

wherein A' is A as defined in formula (I) or a group convertible thereto, R₁' is R₁ as defined in formula (I) or a group convertible thereto, R₆' is -CO₂R₆ as defined in formula (I) or an electron-withdrawing group convertible to -CO₂R₆, L is a leaving group and M is hydrogen or L and M together represent a bond, and Y is a group CN or COL₁, or Y is hydrogen and M is a group CN or COL ₂, where L ₁ and L ₂ are leaving groups and R₁₁ is hydrogen or an N-protecting group; and thereafter, optionally or as necessary, when Y or M is a group COL₁ or COL₂, converting the resulting hydroxy group to a leaving group and reacting the latter with a compound HNR₂'R₃' wherein R₂' and R₃' are R₂ and R₃ as defined in formula (I) or N-protecting groups, removing any R₂' or R₃' N-protecting group, removing any R₁₁ N-protecting group, converting A' when other than A to A, converting R₁' when other than R₁ to R₁, converting R₆' when other than -CO₂R₆ to -CO₂R₆, interconverting A, R₂, R₃ and/or R₆ and/or forming a pharmaceutically acceptable salt of the compound of formula (I).

Suitable examples of the leaving group L include halogens, such as chloro and bromo. hydroxy, C_1-6 acyloxy such as acetoxy or C_1-6 alkoxy, such as methoxy or ethoxy, preferably methoxy. When L is hydroxy, it will be appreciated that the compound of formula (IV) exists in more than one tautomeric form. Suitable examples of A' when other than A include C_2-5 polymethylene optionally interrupted or terminated by NR₄' wherein R₄' is a nitrogen protecting group such as benzyloxycarbonyl. The reaction of compounds of formulae (III) and (IV) comprises a

condensation step followed by a cyclisation step, the acyclic enamine intermediate or imine tautomer thereof optionally being isolated before cyclisation. In a further aspect a compound of formula (I) or a pharmaceutically acceptable salt thereof may be prepared by cyclising the acyclic enamine intermediate or imine tautomer thereof obtainable by the condensation of compounds of formulae (III) and (IV) and thereafter carrying out the optional or necessary steps as previously defined.

The condensation step may be carried out under conditions conventional for condensation reactions, at elevated temperatures in an inert solvent such as toluene, benzene, ethanol, pyridine, dimethylformamide or dioxan, optionally in the presence of a catalyst such as para-toluene-sulphonic acid, with water separation.

The cyclisation of the enamine or imine tautomer thereof may also be carried out under conventional conditions, in the presence of a strong base such as an alkali metal alkoxide, for example sodium methoxide or sodium ethoxide in a suitable solvent such as methanol or ethanol, at elevated temperature, or in the presence of a Lewis acid such as ZnCl₂, SnCl₄ or CUOCOCH₃ in a suitable solvent such as n-butyl acetate at elevated temperature. Lewis acid catalysed cyclisation using copper (I) acetate or tin (IV) chloride is preferred except when A contains oxygen or sulphur, when an alkali metal alkoxide is preferred.

Suitable examples of groups R₆' include the groups hereinbefore described for -CO₂R₆, COR_d where R_d is hydrogen, C_1-6 alkyl, C_3-7 cycloalkyl, C_1-4 alkyl or C_3-7 cycloalkyl, CH=NOH, CO₂H, CO₂Q where Q is a protecting group such as benzyl wherein the benzyl moiety is optionally substituted in the phenyl ring by one or two of halogen, CF₃, C_1-6 alkoxy, C_1-6 alkyl or nitro, cyano and -CONR₈R₉ where R₈ and R₉ are

independently selected from hydrogen, C_1-6 alkyl and phenyl or phenyl C_1-4 alkyl optionally substituted as described above for optional substituents in the phenyl ring of a benzyl ester, or together form a C_2-6 polymethylene chain optionally interrupted by oxygen or NR₁₀ wherein R₁₀ is hydrogen or C_1-6 alkyl, e.g. morpholino or piperazino.

A protecting group Q may be removed by conventional hydrolysis or hydrogenolysis to yield the free acid which can then be esterified under conventional conditions by reaction with the appropriate alcohol R₆OH, optionally with prior conversion of the acid to the acid chloride by reaction with a suitable chlorinating agent such as thionyl chloride, or with an alkylating agent R₆X where X is a leaving group such as chloro, bromo or iodo, in the presence of a suitable base such as potassium hydroxide or carbonate in an inert solvent such as diimethylformamide. Alternatively, Q may be converted directly to R₆ by transesterification under basic conditions. Interconversion of R₆ may be effected similarly.

An intermediate amide may be hydrolysed to the free acid which can then be esterified as described above. An R₆' cyano group may be converted under anhydrous conditions to an imino ester by reaction with the appropriate alcohol R₆OH and then hydrolysed. to the group -CO₂R₆.

An R₆' CH=NOH group may be converted to cyano by dehydration with a suitable dehydrating agent such as formic acid at elevated temperature, and the resulting cyano group converted to CO₂R₆ as just described.

Alternatively the CH=NOH group may be converted to formyl by hydrolysis, oxidised to the free acid using a suitable oxidising agent such as CrO₃ and esterified as above.

R₆' COR_d α-methylene keto groups may be converted to CO₂R₆ via the acid by a haloform reaction and esterification.

Suitable examples of a leaving groups L₁ and L₂ when Y or M is COL₁ or COL ₂, include hydroxy and, more preferably, alkoxy such as C_1-6 alkoxy, for example ethoxy or methoxy. The reaction of the compounds of formulae (III) and (IV) gives a resulting compound having an hydroxy group in the 4-position of the pyridine ring. The hydroxy group may be converted to a leaving group such as those defined above for L, preferably halo such as chloro, by reaction with a halogenating agent such as phosphorus oxychloride or phosphorus oxybromide. The leaving group may be displaced by the compound HNR₂'R₃' under conventional conditions for nucleophilic aromatic displacements, at elevated

temperatures in an inert solvent such as toluene, methanol, ethanol, pyridine, dimethylformamide or dioxan. Alternatively, the reaction may be carried out in neat HNR₂'R₃' which functions as the solvent. An R₂' or R₃' protecting group such as p-methoxybenzyl may be removed conventionally.

Conversion of R₂ and R₃ hydrogen to other R₂/R₃ may be carried out in accordance with conventional procedures for the alkylation or acylation of a primary amine. Acylation may be carried out by reaction with the appropriate acyl halide. However, R₂/R₃ other than hydrogen or acyl groups are preferably introduced via the route in which Y or M is COL₁ or COL₂ in the compound of formula (III) or (IV), by displacement of the leaving group with the compound HNR₂'R₃' ^as discussed above.

An R₄' nitrogen protecting group may be removed conventionally, for example benzyloxycarbonyl may be removed by catalytic hydrogenation, to give R₄ hydrogen which may be alkylated or acylated as necessary to give R₄ C_1-6 alkyl optionally substituted by hydroxy, C_2-7 alkanoyl or C_1-6 alkoxycarbonyl.

Interconversions of R₄ may be effected similarly. Thus, for example, R₄ t-butoxycarbonyl may be removed by treatment with trifiuoroacetic acid to give R₄ hydrogen. Where an R₄ alkyl group is required, it is preferred to protect the nitrogen atom in the compound of formula (III) and effect conversion to R₄ alkyl after cyclisation.

Examples of R₁₁ N-protecting groups include trimethylsilyl and 2- (trimethylsilyl)ethoxymethyl, which may be removed conventionally, for example using tetra-n-butylammonium fluoride. Preferably R₁₁ is hydrogen.

For the preparation of compounds of formula (I) in which R₁ is hydrogen, the compound of formula (IV) may be used in which L and M together represent a bond or L is hydroxy and M is hydrogen, and R₁' is a C_1-6 alkoxycarbonyl group. The reaction with the compound of formula (III) may then be followed by a decarboxylation step to give R₁ hydrogen. Alternatively, a compound of formula (IV) may be used in which L is a leaving group and R₁' is hydroxy. In the resulting compound, the R₁' hydroxy may be converted to hydrogen by first replacing it by chloro by conventional chlorination with a chlorinating agent such as phosphorus oxychloride followed by reductive dehalogenation under conventional conditions, for example zinc in acetic acid.

An R₁' group such as hydroxy or chloro may be converted to alkyl or phenyl C_1-4 alkyl or phenyl, by a palladium mediated anion coupling reaction (V.N. Kalinin, Synthesis, 1992, 413).

Pharmaceutically acceptable salts may be prepared conventionally by reaction with the appropriate acid or derivative.

It will be appreciated that the present invention also provides a process for the preparation of the novel compounds of formula (Ia) which process comprises the reaction of a compound of formula (III) with a compound of formula (TV) or the cyclisation of the acylic enamine intermediate or imine tautomer thereof obtainable by the condensation of compounds of formulae (III) and (IV), as described above.

A class of intermediates comprises compounds of formula (V) or a salt thereof:

wherein A' is as defined in formula (III), R₁' is as defined in formula (IV), R₆" is R₆' as defined in formula (IV) and X is NH₂, OH or chloro, provided that when X is NH₂, A' is A and R₁' is R₁' R₆" is other than -CO₂R₆, when X is NH₂, A is -(CH₂)₃- or -(CH₂)₅- and R₁' is methyl, R₆" is other than CO₂H, and when A is -(CH₂)₃-, X is OH and R₁' is

hydrogen, R₆" is other than CO₂H or CO₂C₂H₅.

The compounds of formula (V) in which A is -(CH₂)₃- and -(CH₂)₅-, R₆" is CO₂H, X is NH₂ and R₁' is methyl have been described by I. Lalezari, J. Het. Chem., 16, 603, (1979).

German Patent DT 2447477 (Schering AG) discloses compounds of formula (V) in which A' is C_2-5 alkylene optionally interrupted by O, S or N wherein any carbon or nitrogen atom is optionally substituted, X is hydroxy and R₆" is carboxy, alkoxycarbonyl or acyloxyalkoxycarbonyl, for use as antimicrobial agents. The preparation of compounds of formula (V) in which Ais -(CH₂)₃-, R₆" is CO₂H and CO₂C₂H₅, X is OH and R₁' is hydrogen is described.

Novel compounds of formula (V) also form part of the invention.

Compounds of formulae (III) and (IV) are known or can be prepared by analogous processes to those used for preparing known compounds. In particular, compounds of formula (III) may be prepared using procedures similar to that in K. Gewald et al.; Chem. Ber. 1966, 94 by reacting

CH₂(CN)₂ and sulphur with the appropriate ketone of formula (VI):

wherein A' is as defined in formula (III). The ketones of formula (VI) are known compounds or may be prepared analogously. For example where A' is -(CH₂)₃NR₄'-, N-benzyl-3-piperidone may be treated with the

appropriate acylating or alkylating reagent such as an alkyl chloroformate using the procedure of A.N. Brubaker and M. CoUey Jnr., J. Med. Chem. 1986 29 1528.

The following Examples illustrate the preparation of pharmacologically active compounds of the invention. Examples 3 to 23 illustrate the preparation of novel compounds of formula (Ia). The following

Descriptions illustrate the preparation of intermediates to the compounds of the present invention.

Description 1

2-Amino-5,6-dihydro-4H-cyclopenta[4,5]th iophene-3-carbonitrile

(D1)

The title compound was prepared in 25% yield from cyclopentanone using a procedure similar to that of K. Gewald et al.; Chem. Ber. 1966, 94.

m.p. 1540.

Description 2 2-Am ino-5,6,7,8-tetrahydro-4H-cyclohepta[4,5]thiophene- 3-carbonitriIe (D2)

The title compound was prepared in 50% yield from cycloheptanone in a similar manner to that of Description 1.

NMR (CDCl₃) δ: 1.30-2.00 (6H, br), 2.40-2.75 (4H, br), 4.50 (2H, s).

Description 3

2-Amino-4,5-dihydro-7H-thieno[2,3-c]pyran-3-carbonitrile (D3)

The title compound was prepared in 68% yield from

tetrahydro-4H-pyran-4-one in a manner similar to that of Description 1. NMR (d₆ DMSO) δ: 2.52 (2H, m), 3.90 (2H, t, J=5Hz), 4.50 (2H, s), 7.20 (2H, s).

Description 4

2-Am ino-6-tert-butyloxycarbonyl-4,5,6,7-tetrahydrothieno[2,3-c] pyridine-3-carbonitrile (D4)

Treatment of a solution of 1-tert-butyloxycarbonyl 4-piperidone (27.93g; 0.14M), malononitrile (9.23g), sulphur (4.5g) in methanol (100ml) with diethylamine (27ml) as described in Description 1 gave the title compound (23.3g; 60%).

NMR (CDCI₃) δ: 1.49 (9H, s), 2.60 (2H, t), 3.66 (2H, t), 4.36 (2H, s), 4.37-4.90 (2H, br). Description 5

6-Acetyl-2-amino-4,5,6,7-tetrahydrothieno[2,3-clpyridine- 3-carbonitrile (D5) The title compound was prepared in 68% yield from 1-acetyl-4-piperidone using a method similar to that of Description 4. m.p. 220-225° (decomp). Found: C, 53.92, H, 5.13, N, 18.72%

C₁₀H₁₁N₃OS requires: C, 54.28; H, 5.01; N, 18.99% The compounds of Descriptions 6 to 8 were prepared according to the following general procedure.

Diethylamine (1.86ml) was added dropwise to a stirred slurry of sulphur (0.6g), malononitrile (1.1g; 17mM) and the appropriate piperidone (17mM) in methanol (60ml). The mixture was stirred at 25° for 16h and then poured into water (500ml). The resultant precipitate was removed by filtration and dried in vacuo.

Description 6

2-A mino-3-cyano-4,5,6,7-tetrahydrothieno[2,3-3]pyridine-7- carboxylic acid, ethyl ester (D6)

56% yield.

NMR (CDCI₃) δ: 1.33 (3H, t, J=8.5), 1.98 (2H, dt, J=5.7), 2.58 (2H, t, J=5.7), 3.77 (2H, t, J=5.7), 4.52 (2H, q, J=8.5).

Description 7 2-Amino-3-cyano-4,5,6,7-tetrahydrotbieno[2,3-b]pyridine-7- carboxylic acid, methyl ester (D7)

53% yield. NMR (d₆ DMSO) δ: 1.90 (2H, dt, J=5.7), 2.42 (2H, t, J=5.7), 3.68 (2H, t,

J=5.7), 3.70 (3H, s), 6.78 (2H, bs).

Description 8

2-Amino-3-cyano-4,5,6,7-tetrahydrothieno[2,3-b]pyridine-7- carboxylic acid, vinyl ester (D8)

57% yield.

NMR (d₆ DMSO) δ: 1.94 (2H, dt, J=5.7), 2.44 (2H, t, J=5.7), 3.80 (2H, t, J=5.7), 4.65 (1H, dd, J=2.8, 8.5), 4.94 (1H, dd, J=2.8, 14.1), 6.90 (2H, bs), 7.15 (1H, dd, J=8.5, 14.1).

Description 9

N-3-(2-(3-Cyano-4,5-dihydro-7H-thieno[2,3-c]thiopyranyl)amino)-2- butenoic acid, methyl ester (D9)

2-Amino-4,5-dihydro-7H-tMeno[2,3-c]thiopyran-3-carbonitrile, prepared in a manner similar to that of D1, methyl 3-oxobutyrate and camphor sulphonic acid were heated under reflux in toluene using a procedure similar to that of Example 1. The crude product gave the title compound in 55% yield after chromatography on Kieselgel 60 using dichloromethane elution. m.p. 147-9° (from ethyl acetate).

Found: C, 52.86; H, 4.70; N, 9.56%

C₁₃H₁₄N₂S₂O₂ requires: C, 53.04; H, 4.79; N, 9.52%

Example 1 4-Amino-6,7-dihydro-2-methyl-5H-cyclopenta[4,5] thieno

[2,3-b]pyridine-3-carboxylic acid, ethyl ester (E1)

A solution of D1 (6.85g; 41.8mM) and ethyl 3-ethoxycrotonate (7.93g;

50.2mM) in toluene (150ml) containing p-toluenesulphonic acid (20mg) was heated under reflux (Dean/Stark) for 2h. The mixture was

concentrated in vacuo, partitioned between ethyl acetate and water and the organic phase dried (Na₂SO₄) and evaporated to dryness. The residue in n-butyl acetate (100ml) and tin (IV) chloride (13.8g; 53mM), was heated under reflux for 30 min and allowed to cool. The mixture was partitioned between 10% aqueous sodium hydroxide and ethyl acetate. The organic phase was dried (Na₂SO₄), evaporated to dryness and chromatography of the residue on Kieselgel 60 in dichloromethane gave the title compound (2g; 17%) on recrystallisation from ethanol. m.p. 129-131°.

Found: C, 61.00; H, 5.93; N, 10.17%

C₁₄H₁₆N₂O₂S requires: C, 60.85; H, 5.84; N, 10.14%

NMR (CDCl₃) δ: 1.40 (3H, t), 2.42-2.55 (2H, m), 2.70 (3H, s), 2.92 (2H, t),

3.03 (2H, t), 4.30-4.42 (2H, q), 6.37 (2H, br, s).

Example 2

4-Amino-2-methyl-6,7,8,9-tetrahydro-5H-cyclohepta[4,5]

thieno[2,3-b]pyridine-3-carboxylic acid, ethyl ester (E2)

The title compound was prepared from D2 in 20% yield using a method similar to that of Example 1. m.p. 141-143°

Found: C, 63.32; H, 6.80; N, 9.10%

C₁₆H₂ON₂O₂S requires: C, 63.13; H, 6.62; N, 9.20%.

Example 3

4-Amino-2-methyl-6,7,8,9-tetrahydro-5H-cyclohepta[4,5]thieno

[2,3-b]pyridine-3-carboxylic acid, 2-propynyl ester (E3)

The title compound E3 was prepared in 65% yield from the ethyl ester E2 by hydrolysis using aqueous ethanolic sodium hydroxide at reflux followed by alkylation with 2-propynyl bromide, using potassium carbonate as base, in dimethylformamide at room temperature. m.p. 159-160°C.

Found: C, 64.79; H, 5.77; N, 8.87%

C₁₇H₁₈N₂O₂S requires: C, 64.94; H, 5.77; N, 8.91%

Example 4 4-Amino-6,7-dihydro-2-methyl-5H-cyclopenta[4,51 thieno

[2,3-b]pyridine-3-carboxylic acid, 2-propynyl ester (E4)

E1 was converted into the title compound in 65% yield using a method similar to that of Example 3. m.p. 163-164°

Found: C, 62.84; H, 4.99; N, 9.71%

C₁₅H₁₄N₂O₂S requires: C, 62.92; H, 4.93; N, 9.78% Example 5

5-Amino -3,4-dihydro-7-methyl-1H-pyrano[4',3^,:4,5]

thieno[2,3-b]pyridine-6-carboxylic acid, ethyl ester (E5)

A solution of D3 (2g; 11.2mM) and ethyl 3-ethoxycrotonate (2.3g; 14.6mM) in toluene (50ml) containing p-toluenesulphonic acid (0.3g; 1.56mM) was heated under reflux for 3h. The reaction mixture was cooled and treated with a 1M solution of sodium ethoxide in ethanol (15ml). The mixture was heated under reflux, under nitrogen, for 1h, allowed to cool to room temperature, and then partitioned between ethyl acetate at water at pH 8.

The organic phase was dried (Na₂SO₄) and evaporated to dryness.

Chromatography of the residue on Kieselgel 60 in dichloromethane gave a white solid (1.1g) which, on recrystallisation from ethanol, gave the title compound E5 (0.69g; 21%). m.p. 133-134°

Found: C, 57.59; H, 5.64; N, 9.66%

C₁₄H₁₆N₂O₃S requires: C, 57.52; 5.52; N, 9.58% Example 6

4-Amino -7-tert-butyloxycarbonyl-2-methyl-5,6,7,8-tetrahydro- thieno[2,3-b:5,4-c']dipyridine-3-carboxylic acid, ethyl ester (E6) The aminonitrile D4 (10g; 35.4mM) and ethyl 3-ethoxycrotonate (8.51g; 53.9mM) were converted into the title compound (8.16g; 59%) using a method similar to that described in Example 1, except that copper (I) acetate (1.96g; 16mM) was used for the cyclisation step.

NMR (CDCl₃) δ: 1.44 (3H, t, J=7.5), 1.50 (9H, s), 2.74 (3H, s), 3.08 (2H, t, J=6), 3.78 (2H, t, J=6), 4.40 (2H, q, J=7.5), 4.64 (2H, s), 6.40-6.65

(2H, br, s).

Example 7

4-Amino-2-methyl-5,6,7,8-tetrahydrotbieno[2,3-b:5,4-c']

dipyridine-3-carboxylic acid, ethyl ester (E7)

A solution of E6 (2g; 5.11mM) in trifluoroacetic acid (50ml) was stirred at 25° for 1h and then evaporated in vacuo. The residue was partitioned between ammonia and ethyl acetate. The organic phase was washed with brine, dried (Na2Sθ4) and evaporated in vacuo. Recrystallisation from ethyl acetate-petroleum ether gave the title compound as off-white crystals (1.06g; 71%). m.p. 149°

Found: C, 57.77; H, 5.89; N, 14.40%

C₁₄H₁₇N₃O₂ requires: C, 57.71; H, 5.88; N, 14.42%.

NMR (CDCl₃) δ: 1.42 (3H, t, J=7.5), 2.70 (3H, s), 3.00 (2H, br), 3.20 (2H, br), 4.02 (2H, s), 4.40 (2H, q, J=7.5), 6.52 (2H, s, br). Example 8

4-Amino-2,7-dimethyl-5,6,7,8-tetrahydrothieno[2,3-b:

5,4-c']dipyridine-3-carboxylic acid, ethyl ester (E8) A solution of E7 (2g; 6.8mM) in acetonitrile (3ml) and aqueous

formaldehyde (0.55ml; 6.8mM) at 0° was treated with sodium

cyanoborohydride (90mg; 1.4mM). The pH was adjusted to 5 with acetic acid and stirring continued for 2h. Work-up with ether was followed by chromatography on silica using dichloromethane. RecrystaUisation from ethyl acetate - petroleum ether gave the title compound (1g; 48%).

m.p. 125°.

Found: C, 58.84; H, 6.38; N, 13.69%

C₁₅H₁₉N₃O₂S requires C, 58.99; H, 6.27; N, 13.76% Example 9

7-Acetyl-4-amino-2-methyl-5,6,7,8-tetrahydrothieno

[2,3-b:5,4-c']dipyridine-3-carboxylic acid, ethyl ester (E9)

A solution of E7 (1.5g; 5.1 mM) in dichloromethane (20ml) containing triethylamine (0.75ml) was stirred at -30° and acetic anhydride (0.5ml) added. Stirring was continued for 10min and the mixture was washed with water, dried (Na₂SO₄) and evaporated in vacuo. Recrystallisation of the residue from ethyl acetate gave the title compound (1.37g; 75%).

m.p. 178°

Found: C, 57.56; H, 5.71; N, 12.59%

C₁₆H₁₉N₃O₃S requires: C, 57.64; H, 5.74; N, 12.60%

A portion was converted into a tartrate salt and recrystallised from ethanol. m,p. 118-21°.

Found: C, 47.70; H, 5.28; N, 8.13%

C₂₀H₂₅N₂O₉S.H₂O requires: C, 47.90; H, 5.43; N, 8.38%

Example 10

7-Acetyl-4-amino-2-phenyI-5,6,7,8-tetrahydrothieno[2,3-b:5,4-c'] dipyridine-3-carboxylic acid, ethyl ester (E10)

The title compound was prepared in 32% overall yield from the amino nitrile D5 and ethyl 3-ethoxycinnamate using a method similar to that of Example 1. m.p. 184-6° (from ethyl acetate)

Found: C, 63.47; H, 5.41; N, 10.43%

C₂₁H₂₁N₃O₃S requires: C, 63.78; H, 5.35; N, 10.63%

Example 11

4-Amino-2-methyl-5,6,7,8-tetrahydrothieno[2,3-b:5,4-c']

dipyridine-3-carboxylic acid, 2-propynyl ester (E11)

Treatment of E6 according to the method of Examples 3 and 7 gave the title compound in 26% overall yield. m.p. 159-60° (from ethanol) Found: C, 59.40; H, 5.07; N, 14.08%

C₁₅H₁₅N₃O₂S requires: C, 59.78; H, 5.02; N, 13.94%

Example 12

4-Amino-2-methyl-5,6,7,8-tetrahydrotbieno[2,3-b:5,4-c^,]dipyridine- 3,7-dicarboxylic acid, ethyl, methyl diester(E12)

Treatment of E7 (0.5g; 1.72mM) with methyl chloroformate (0.15ml;

1.89mM) according to the procedure of Example 9 gave the title compound (0.54g; 90%). m.p. 143-4°.

Found: C, 54.92; H, 5.46; N, 12.02%

C₁₆H₁₉N₃O₄S requires: C, 55.00; H, 5.48; N, 12.03% Example 13

4-Amino-2-methyl-5,6,7,8-tetrahydrothieno[2,3-b:5,4-c']

dipyridine-3,7-dicarboxylic acid, diethyl ester (E12) Treatment of E7 with ethyl chloroformate according to the procedure of Example 9 gave the title compound in 44% yield. m.p. 128° (from ethyl acetate-petroleum ether).

Found: C, 56.09; H, 5.75; N, 11.42%

C₁₇H₂₁N₃O₄S requires: C, 56.18; H, 5.82; N, 11.56%

Example 14

4-Amino-7-formyl-2-methyl-5,6,7,8-tetrahydrotbieno[2,3- b:5,4-c']dipyridine-3-carboxylic acid, ethyl ester (E14)

Formic acetic anhydride was prepared using the procedure of L.I. Krimen, Org. Syn; Vol. 50, 1 and then reaction with E7 according to the method of Example 9 gave the title compound in 61% yield. m.p. 182-3° (from ethyl acetate).

Found: C, 56.39; H, 5.31; N, 12.96%

C₁₅H₁₇N₃O₃S requires: C, 56.41; H, 5.37; N, 13.16% Example 15

4-Amino-2-methyl-7-propionyl-5,6,7,8-tetrahydrothieno[2,3-b:

5,4-c']dipyridine-3-carboxylic acid, ethyl ester (E15)

The title compound was prepared in 89% yield from E7 and propionyl chloride according to the method of Example 9. m.p. 171-2° (from ethyl acetate-petroleum ether).

Found: C, 58.90; H, 6.13; N, 11.95%

C₁₇H₂₁N₃O₃S requires: C, 58.77; H, 6.09; N, 12.09%

Example 16

4-Amino-2-methyl-5,6,7,8-tetrahydrothieno[2,3-b:5,4-b']

dipyridine-3,8-dicarboxylic acid, diethyl ester (E16)

A solution of D6 and ethyl 3-ethoxycrotonate in toluene was converted into the title compound, in 52% overall yield, using a method similar to that of Example 1. m.p. 185-70°.

Found: C, 56.10; H, 5.81; N, 11.47%

C₁₇H₂₁N₃O₄S requires: C, 56.18; H, 5.82; N, 11.56%

Example 17 4-Amino-2-methyl-5,6,7,8-tetrahydrothieno[2,3-b:5,4-b']

dipyridine-3,8-dicarboxylic acid, ethyl,methyl diester (E17)

A solution of ethyl 3-ethoxycrotonate and D7 in toluene was converted into the title compound, in 42% overall yield, using a method similar to that of Example 1. m.p. 195-7°.

Found: C, 55.13; H, 5.47; N, 11.97%

C₁₆H₁₉N₃O₄S requires: C, 55.00; H, 5.48; N, 12.03% Example 18

4-Amino-2-methyl-5,6,7,8-tetrahydrothieno[2,3-b:5,4-b']

dipyridine-3,8-dicarboxylic acid, ethyl, vinyl diester (E18)

The title compound was prepared from D8 in 25% yield using the method of Example 1 m.p. 198-200°.

Found: C, 56.46; H, 5.31; N, 11.51%

C₁₇H₁₉N₃O₄S requires: C, 56.50; H, 5.30; N, 11.63%

Example 19

7-Acetyl-4-amino-2-methyl-5,6,7,8-tetrahydrothieno[2,3-b:5,4-c'] dipyridine-3-carboxylic acid, 2-butynyl ester (E19).

The amino nitrile D4 and 2-butynyl-3-oxobutyrate were reacted, in 52% yield, according to the procedure of E1 using camphor sulphonic acid and copper (I) acetate to give 4-amino-7-tert-butyloxycarbonyl-2-methyl- 5,6,7,8-tetrahydrothieno[2,3-b:5,4-c']dipyridine-3-carboxylic acid, 2- butynyl ester (E19a). This was followed by deprotection using

trifluoroacetic acid as in Example 7 to give 4-amino-2-methyl-5,6,7,8- tetrahydrothieno[2,3-b:5,4-c']dipyridine-3-carboxylic acid, 2-butynyl ester (E19b). Acetylation of E 19b as in Example 9 gave the title compound in 60% overall yield. m.p. 200-1°

Found: C, 60.43; H, 5.32; N, 11.73%

C₁₈H₁₉N₃O₃S requires: C, 60.49; H, 5.36; N, 11.76%

Example 20 4-Amino-2-methyl-5,6,7,8-tetrahydrothieno[2,3-b:5,4-c'] dipyridine- 3,7-dicarboxylic acid, 2-butynyl, methyl diester (E20)

Treatment of D4 according to the method of Example 19, using methyl chloroformate for the acylation step, gave the title compound in 20% overall yield. m.p. 202-4°

Found: C, 58.01, H, 5.23; N, 11.23%

C₁₈H₁₉N₃O₄S requires: C, 57.90; H, 5.13; N, 11.25%. Example 21

5-Amino-3,4-dihydro-7-methyl-1H-tbiopyrano[4^,,3^,:4,5] thieno[2,3- blpyridine-6-carboxylic acid, ethyl ester (E21)

A solution of D9 in toluene was treated with sodium ethoxide according to the method of Example 5. Chromatography on Alumina using

dichloromethane elution followed by recrystallisation from ethyl acetate, gave the title compound in 69% overall yield, m.p. 167.5-169°

Found: C, 54.55; H, 5.22; N, 9.17%

C₁₄H₁₆N₂S₂O₂ requires: C, 54.52; H, 5.23; N, 9.08%

Example 22 5-Amino -3,4-dihydro-7-methyl-1H-thiopyrano[4^,,3^,:4,5]thieno[2,3- blpyridine-6-carboxylic acid, methyl ester (E22)

The title compound was prepared in a similar manner to that of E21 using sodium methoxide to effect the cyclisation of D9. m.p. 220-2°

Found: C, 53.17; H, 4.81; N, 9.60%

C₁₃H₁₄N₂S₂O₂ requires: C, 53.04; H, 4.79, N, 9.52%

Example 23 7-Methylsulfonyl-4-amino-2-phenyl-5,6,7,8-tetrahydrothieno[2,3- b:5,4-c'] dipyridine-3-carboxylic acid, ethyl ester (E23)

The title compound was prepared in 68% overall yield from the amine E7 and methanesulfonyl chloride using a method similar to that of Example 9. m.p. 185-6° (from ethyl acetate).

Found: C, 48.62; H, 5.11; N. 11.30%

C₁₅ H₁₉ N₃ O₄ S₂ requires C, 48.76; H, 5.18; N, 11.37%

NMR (CDCI₃) δ: 1.43 (3H, t, J = 10Hz), 2.72 (3H, s), 2.90 (3H, s), 3.21 (2H, m), 3.71 (2H, t, J=5Hz), 4.41 (2H, q, J=10,5Hz), 4.57 (2H, bs), 6.53 (2H, bs)

Examples 16-18

R₄

E16 CO₂C₂H₅

E17 CO₂CH₃

E18 CO₂CH=CH₂

Examples 21 and 22

R₁

E21 CH₃ C₂H₅ E22 CH₃ CH₃

Pharmacological Data

Geller-Seif ter Procedure

Potential anxiolytic properties are evaluated using the Geller-Seifter procedure based on that originally described by Geller and Seifter, (1960) Psychopharmacologia, 1, 482-492. This procedure has been shown to be selective for drugs with anxiolytic properties (Cook and Sepinwall, (1975) "Mechanism of Action of Benzodiazepines" ed. Costa, E. and Greengard, P., Raven Press, New York, pp. 1-28).

Rats are trained on a variable interval 30 sec schedule (VI30) to press a lever in order to obtain food reward. The 5 min sessions of the VI30 schedule alternate with 2-5 min of a schedule (FR5) in which every 5th lever press is followed by presentation of a food pellet paired with a 0.5 sec mild footshock. The total study lasts approximately 30 mins . Rats typically respond with high rates of lever pressing under the VI30 schedule and low response rates under the FR5 'conflict' session.

Anxiolytic drugs increase the suppressed response rates of rats in 'conflict' session.

Drugs are administered intraperitoneally or orally to groups of 3-8 rats 30 min before testing.

The results are expressed as the percentage increase in square root of the total number of lever presses in the FR5 'conflict' session. Square root transformation is necessary to normalise the data for statistical analysis using parametric methods (ANOVA).

Compounds E3, E4, E5, E9, E12, E14 and E17 showed an increase in responding in the 'conflict' session at a dose of 20 mg/kg p.o. Compounds E1, E2, E7, E8, E10, E11, E13, E15, E16 and E18-E23 showed no significant increase in responding at 20 mg/kg p.o. but would be expected to be active at higher dose or by other routes of administration. [³⁵S]-TBPS binding studies in vitro

[³⁵s]-TBPS labels a site on or near the Cl- channel portion of the

GABA_A/BDZ/CI- channel complex. Literature studies have shown that [³⁵S]-TBPS binding is directly related to the permeability of the Cl- channel (e.g. Concas et al, 1988). Anxiolytic agents such as

benzodiazepines and barbiturates aUostericaUy inhibit the binding, whilst anxiogenic agents (e.g. benzodiazepine inverse agonists) potentiate the binding.

Modulation of [³⁵s]-TBPS binding is measured by a method similar to that of Gee et al (1986), using well-washed rat cerebral cortex membranes. Specific binding using 2nM [³⁵S]-TBPS (in the presence of either 1μM or 5μM GABA) represents 70-80% of total binding. Non-specific binding is defined by using 100μM picrotoxin. IC₅₀ values are calculated from log concentration versus % inhibition curves.

Concas A. et al, (1988) J. Neurochem. 51(6), 1868-1876.

Gee K.W. et al, (1986) Mol. Pharmacol. 30, 218-225. Compounds E2-E5, E9, E10, E12, E13, E15, E16, E19-E21 and E23 showed an IC₅₀ of less than 20μM and E6-E8, E11, E14 greater than 20μM . Solubility problems prevented the determination of reHable IC₅₀ values for the remaining compounds. MES TEST

The maximal electroshock seizure (MES) test in rodents is one of the most widely used models of human grand mal epUepsy¹. In this model, anticonvulsant agents elevate the threshold to electrically-induced seizures whilst proconvulsants lower the seizure threshold.

Method

Mice (male, Charles River, U. K. CD-1 strain, 25-30g) are randomly assigned to groups of 10-20 and dosed oraUy or intraperitoneally at a dose volume of 10ml/kg with various doses of compound (1-100 mg/kg) or vehicle. Mice are then subjected at 30 or 60 min post dose to a variable voltage electroshock (0.1 sec, 50 Hz, sine wave form) via a buccal and a subcutaneous electrode. The mean voltage and standard error required to induce a tonic seizure in 50% (CV₅₀) of the mice in the group is

determined by the 'up and down' method of Dixon and Mood (1948)².

Statistical comparisons between vehicle- and drug-treated groups are made using the method of Litchfield and Wilcoxon (1949)³.

In control animals the CV₅₀ is usually 40 - 50V. Hence the first animal in the control group is subjected to a voltage of 45V. If a tonic seizure does not ensue, the voltage is increased for a subsequent mouse. If a tonic convulsion does occur, then the voltage is decreased, and so on until all the animals in the group have been tested.

The percentage increase or decrease in CV₅₀ for each group compared to the control is calculated.

Studies are carried out using a Heathkit shock generator with totally variable control of shock level from 0 to 200V and voltage steps of 5V are used. Drugs are suspended in 1% methyl cellulose.

Reference

1. Swinyard, E.A. (1972). Electrically-induced convulsions. In:

Experimental Models of Epilepsy ed. Purpura, D.P. et al., 433-458, Raven Press, New York.

2. Dixon, W.J. and Mood, A.M. (1948). J. Amer. Stat. Assn., 43, 109- 126.

3. Litchfield, J.T. and Wilcoxon, F. (1949). J. Pharmacol. Exp. Ther.

96, 99-113.

Results

Compound E12 was significantly active at 300 mg/kg p.o.

Claims

Claims

1. A compound of formula (I) or a pharmaceuticaUy acceptable salt

thereof:

wherein the variables are as defined in the description; for

pharmaceutical use.

2. A compound of formula (I) as defined in claim 1 or a pharmaceutically acceptable salt thereof with the proviso that, when A is -(CH₂)₃- or -

(CH₂)₅-, R₁ is methyl and R₂ and R₃ are hydrogen, R₆ is other than ethyl.

3. A compound according to claim 2 wherein A is selected from -(CH₂)₃-, -(CH₂)₅-, -(CH₂)n-O-(CH₂)_m-, -(CH₂)_n-S-(CH₂)_m- and

-(CH₂)_n-NR₄-(CH₂)_m- wherein n and m are independently zero or an integer of 1 to 4 such that (n+m) is an integer of 2 to 4, R₄ is hydrogen, C_1-4 alkyl, C_1-5 alkanoyl, C_1-4 alkylsulphonyl, C_1-4 alkoxycarbonyl or C_2-4 alkenyloxycarbonyl and any methylene group is optionally substituted by R₅ where R₅ is C_1-4 alkyl.

4. A compound according to claim 2 or 3 wherein R₁ is hydrogen, C_1-3 alkyl, phenyl or benzyl.

5. A compound according to any of claims 2 to 4 where R₂ and R₃ are independently hydrogen or C_1-6 alkyl.

6. A compound according to any of claims 2 to 6 where R₆ is C_1-6 alkyl optionally substituted by up to three halo atoms, C_2-6 alkenyl, C_2-6 alkynyl, C_3-4 cycloalkyl or C_3-4 cycloalkyl-C_1-4 alkyl.

7. A compound selected from E3 to E23 as defined in the description or a pharmaceutically acceptable salt thereof.

8. A process for the preparation of a compound according to claim 2, which process comprises cyclising the acyclic enamine intermediate or imine tautomer thereof obtainable by the condensation of compounds of formulae (III) and (IV) as defined in the description and thereafter, optionally or as necessary, when Y or M is a group COL₁ or COL₂, converting the resulting hydroxy group to a leaving group and reacting the latter with a compound HNR₂'R₃' wherein R₂' and R₃' are R₂ and R₃ as defined in formula (I) or N-protecting groups, removing any R2' or R₃' N-protecting group, removing any R₁₁ N-protecting group, converting A' when other than A to A, converting R₁' when other than R₁ to R₁, converting R₆' when other than -CO₂R₆ to -CO₂R₆, interconverting A, R₂, R₃ and/or R₆ and/or forming a pharmaceutically acceptable salt of the compound according to claim 2.

9. A pharmaceutical composition comprising a compound of formula (I) as defined in claim 1 or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

10. A compound of formula (I) as defined in claim 1 or a pharmaceutically acceptable salt thereof, for use in the treatment or prophylaxis of CNS disorders.

11. The use of a compound of formula (I) as defined in claim 1 or a

pharmaceutically acceptable salt thereof, in the manufacture of a medicament for the treatment or prophylaxis of CNS disorders.