TETRAHYDROPYRIDO(1,2-A)INDOLE DERIVATIVES, PROCESS FOR THEIR PREPARATION AND PHARMACEUTICAL COMPOSITIONS CONTAINING THEM

Abstract: A pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof: wherein: R₁ is hydrogen, C 1-6 alkyl, C 1-6 alkoxy or halogen; R₂ and R₃ are both hydrogen or together represent a bond; R₄ is hydrogen and R₅ is hydrogen or R₄ and R₅ together represent an oxo group; R₆ is phenyl C 1-7 alkanoyl in which the phenyl moiety is optionally substituted by one or two of halogen, nitro, meta - or para -methoxy, methyl or NR₈R₉ wherein R₈ and R₉ are independently hydrogen or C 1-6 alkyl or R₈ and R₉ together are C 2-6 polymethylene, or 3,4-disubstituted by methylenedioxy or ethylenedioxy; or C 1-7 alkanoyl substituted by NR₁₀R₁₁ where R₁₀ and R₁₁ are independently hydrogen or C 1-4 alkyl or together are C 3-7 polymethylene optionally containing a further hetereoatom which is oxygen, sulphur or nitrogen substituted by R₁₂ where R₁₂ is hydrogen, C 1-4 alkyl or benzyl, and optionally substituted by one or two C 1-4 alkyl, C 2-5 alkanoyl, C 1-4 alkoxycarbonyl, aminocarbonyl optionally substituted by one or two C 1-6 alkyl groups or by a benzyl group, cyano, phenyl or benzyl and wherein any phenyl or benzyl group is optionally substituted in the phenyl ring by one or two halo, CF₃, C 1-4 alkyl, C 1-4 alkoxy, cyano or nitro groups; and R₇ is hydrogen or C 1-4 alkyl; and a pharmaceutically acceptable carrier.

Description: This invention relates to compounds having pharmacological activity, to a process for their preparation and their use as pharmaceuticals. EP-0167901 and EP-0213696 disclose certain secocanthine derivatives having anti-hypoxic activity and/or activity against cerebral oxygen deficiency. A further group of secocanthine derivatives have been discovered to have anti-ischaemic activity, in particular anti-hypoxic activity and/or activity against cerebral oxygen deficiency and to improve data acquisition or retrieval following transient forebrain ischaemia. Accordingly, the present invention provides a pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof: wherein: R₁ is hydrogen, C 1-6 alkyl, C 1-6 alkoxy or halogen; R₂ and R₃ are both hydrogen or together represent a bond; R₄ is hydrogen and R₅ is hydrogen or R₄ and R₅ together represent an oxo group; R₆ is phenyl C 1-7 alkanoyl in which the phenyl moiety is optionally substituted by one or two of halogen, nitro, meta - or para -methoxy, methyl or NR₈R₉ wherein R₈ and R₉ are independently hydrogen or C 1-6 alkyl or R₈ and R₉ together are C 2-6 polymethylene, or 3,4-disubstituted by methylenedioxy or ethylenedioxy; or C 1-7 alkanoyl substituted by NR₁₀R₁₁ where R₁₀ and R₁₁ are independently hydrogen or C 1-4 alkyl or together are C 3-7 polymethylene optionally containing a further hetereoatom which is oxygen, sulphur or nitrogen substituted by R₁₂ where R₁₂ is hydrogen, C 1-4 alkyl or benzyl, and optionally substituted by one or two C 1-4 alkyl, C 2-5 alkanoyl, C 1-4 alkoxycarbonyl, aminocarbonyl optionally substituted by one or two C 1-6 alkyl groups or by a benzyl group, cyano, phenyl or benzyl and wherein any phenyl or benzyl group is optionally substituted in the phenyl ring by one or two halo, CF₃, C 1-4 alkyl, C 1-4 alkoxy, cyano or nitro groups; and R₇ is hydrogen or C 1-4 alkyl; and a pharmaceutically acceptable carrier. The compounds of formula (I) have anti-ischaemic activity, in particular anti-hypoxic activity and/or activity against cerebral oxygen deficiency. The compounds of formula (I) also improve data acquisition or retrieval following transient forebrain ischaemia. The compounds are therefore useful in the treatment of cerebral vascular and neuronal degenerative disorders associated with learning, memory and cognitive dysfunctions including cerebral senility, multi-infarct dementia and senile dementia of the Alzheimer type. The compositions may be in the form of tablets, capsules, powders, granules, lozenges, suppositories, reconstitutable powders, or liquid preparations such as oral or sterile parenteral solutions or suspensions. In order to obtain consistency of administration it is preferred that a composition of the invention is in the form of a unit dose. Unit dose presentation forms for oral administration may be tablets and capsules 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; disintegrants, for example starch, polyvinylpyrrolidone, sodium starch glycollate or microcrystalline cellulose; or pharmaceutically acceptable wetting agents such as sodium lauryl sulphate. The solid oral compositions may be prepared by conventional methods of blending, filling, tabletting or the like. Repeated blending operations may be used to distribute the active agent throughout those compositions employing large quantities of fillers. Such operations are of course conventional in the art. The tablets may be coated according to methods well known in normal pharmaceutical practice, in particular with an enteric coating. Oral liquid preparations may be in the form of, for example, 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, syrup, methyl cellulose, gelatin, hydroxyethylcellulose, carboxymethylcellulose, aluminium stearate gel, hydrogenated edible fats; emulsifying agents, for example lecithin, sorbitan monooleate, or acacia; non-aqueous vehicles (which may include edible oils), for example almond oil, fractionated coconut oil, oily esters such as esters of 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. For parenteral administration, fluid unit dosage forms are prepared utilizing the compound and a sterile vehicle, and, depending on the 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 sterilized before filling into a suitable vial or ampoule and sealing. Advantageously, adjuvants such as a local anaesthetic, a preservative and buffering agents can 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. 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 sterilized by exposure to ethylene oxide before suspending in the sterile vehicle. Advantageously, a surfactant or wetting agent is included in the composition to facilitate uniform distribution of the compound. The compositions may contain from 0.1% to 99% by weight, preferably from 10-60% by weight, of the active material, depending on the method of administration. The invention also provides a method of treatment of cerebrovascular disorders and/or disorders associated with cerebral senility 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. The invention further provides a method of treatment in mammals including humans of cerebral vascular and neuronal degenerative disorders associated with learning, memory and cognitive dysfunctions including cerebral senility, multi-infarct dementia and senile dementia of the Alzheimer type, which comprises administering to the sufferer an effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof. The dose of the compound used in the treatment of such disorders will vary in the usual way with the seriousness of the disorders, the weight of the sufferer, and the relative efficacy of the compound. However, as a general guide suitable unit doses may be 0.05 to 100 mg. for example 0.2 to 50mg; and such unit doses may be administered more than once a day, for example two or three times a day, so that the total daily dosage is in the range of 0.1 to 100 mg/kg; and such therapy may extend for a number of weeks or months. In a further aspect the invention provides a compound of formula (I), including pharmaceutical salts thereof, for use as an active therapeutic substance. The invention further provides a compound of formula (I) or a pharmaceutically acceptable salt thereof, for use in the treatment of cerebrovascular disorders and/or disorders associated with cerebral senility. In another aspect the invention provides a compound of formula (I), including pharmaceutically acceptable salts thereof, for use in the treatment of cerebral vascular and neuronal degenerative disorders associated with learning, memory and cognitive dysfunctions including cerebral senility, multi-infarct dementia and senile dementia of the Alzheimer type. At the above described dosage range, no toxicological effects are indicated for the compounds of the invention. Suitable examples of R₁ include hydrogen, methyl, ethyl, n - and iso - propyl, n -, sec -, iso - and tert -butyl, methoxy, ethoxy, fluoro and chloro. R₁ is preferably hydrogen or methyl, most preferably hydrogen. R₂ and R₃ preferably together represent a bond. Suitable examples of R₆ include benzoyl, phenacetyl, 3-phenylpropionyl or 1-methyl-2-phenylacetyl in which the phenyl moiety is optionally substituted by one or two of fluoro, chloro, bromo, amino, methylamino, ethylamino, neo -pentylamino, dimethylamino, diethylamino, di-isopropylamino, 1-piperidyl, 1-pyrrolidyl, ortho - or meta -nitro, meta or para -methoxy, or methyl, or 3,4-disubstituted by methylenedioxy. Suitable examples of cyclic aminoalkanoyl R₆ include NR₁₀R₁₁C 1-7 alkanoyl where R₁₀ and R₁₁ together form a piperidine, pyrrolidine, piperazine or morpholine ring. Suitable examples of optional substituents on cyclic amino C 1-7 alkanoyl R₆ include one or two C 1-4 alkyl groups such as methyl, ethyl, n - and iso -propyl, and n -, sec -, iso - and t -butyl. Suitable examples of cyclic NR₁₀R₁₁ includes 1-piperidyl, 2-methyl-1-piperidyl, 3-methyl-1-piperidyl, 3,5-dimethyl-1-piperidyl, 2,6-dimethyl- 1-piperidyl, 2,5-dimethyl-1-pyrrolidyl, 2,4-dimethyl-1-pyrrolidyl and 1-morpholinyl. Suitable examples of acyclic amino alkanoyl R₆ include C 1-4 alkyl amino C 1-7 alkanoyl and di-C 1-4 alkylamino C 1-7 alkanoyl, such as methylamino-, ethylamino-, n - or iso -propylamino-, iso -butylamino-, dimethylamino-, diethylamino, di- n - or iso -propylamino- and di- iso -butylamino C 1-7 alkanoyl. Preferably R₆ is benzoyl or 1-methyl -2-phenylacetyl optionally monosubstituted in the phenyl moiety by NR₈R₉; or C 3-7 alkanoyl, such as C 4-6 or C 5-7 alkyl, substituted by NR₁₀ R₁₁, suitable carbon chain lengths in R₆ including C₃, C₄ and C₅. When NR₁₀ R₁₁ is a cyclic moiety, it preferably comprises 5 to 7 ring atoms, more preferably 5 or 6 ring atoms. Suitable examples of R₇ include hydrogen, methyl, ethyl, n - and iso -propyl, n -, sec -, iso - and tert -butyl, preferably hydrogen. The compounds of formula (I) can form acid addition salts with acids, such as the conventional pharmaceutically acceptable acids, for example hydrochloric, hydrobromic, phosphoric, acetic, fumaric, salicylic, citric, lactic, mandelic, tartaric, oxalic and methanesulphonic. There is a favourable group of compounds within formula (I) of formula (II): wherein R₁, R₂, R₃, R₄, R₅ and R₇ are as defined in formula (I) and R₆¹ is phenyl C 1-7 alkanoyl optionally monosubstituted by fluoro, chloro, bromo, NR₈R₉ where R₈ and R₉ are as defined in formula (I), methoxy or nitro; or NR₁₀¹ R₁₁¹ C 1-7 alkanoyl where R₁₀¹ and R₁₁¹ together are C 3-7 polymethylene optionally containing a further heteroatom as defined above for R₁₀ and R₁₁ and optionally substituted by one or two C 1-4 alkyl groups. Suitable and preferred values for R₁, R₂, R₃, R₆¹, R₇, R₈ and R₉ are as described under formula (I) for R₁, R₂, R₃, R₆, R₇, R₈ and R₉. There is a sub-group of compounds within formula (II) of formula (IIa): wherein R₁, R₂, R₃, R₆¹ and R₇ are as defined in formula (II). Suitable and preferred values for the variables are as described for the corresponding variables under formula (I). There is a sub-group of compounds within formula (IIa) of formula (IIb): wherein R₁, R₂, R₃ and R₇ are as defined in formula (I) and R₆² is phenyl C 1-4 alkanoyl optionally mono-substituted by NR₈R₉ where R₈ and R₉ are as defined in formula (I); or (1-piperidyl)C 1-7 alkanoyl substituted by one or two C 1-4 alkyl groups. Suitable and preferred values for the variables are as described for the corresponding variables under formula (I). Preferably R₆² is benzoyl or 1-methyl-2-phenylacetyl optionally meta - or para -substituted by amino optionally substituted by one or two methyl or ethyl groups; or 5-(3,5-dimethyl-1-piperidyl)-1-oxo-pentyl. There is another sub-group of compounds within formula (IIa) of formula (IIc): wherein R₁, R₂, R₃, and R₇ are as defined in formula (I) and R₆³ is -CO(CH₂)₄NR₁₀¹R₁₁¹ where R₁₀¹ and R₁₁¹ are as defined in formula (II). Preferably R₁ is hydrogen. Preferably R₂ and R₃ represent a bond. Preferably R₇ is hydrogen. There is a further group of compounds within formula (II) of formula (IId): wherein R₆¹ is as defined in formula (II) and the remaining variables are as defined in formula (I). Suitable and preferred values for R₆¹ and R₇ are as described under formulae (II) and (IIa). Another subgroup of compounds within formula (I) is of formula (III): wherein R₁, R₂, R₃, R₄, R₅, and R₇ are as defined in formula (I) and R₆⁴ is NR₁₀² R₁₁² C 1-7 alkanoyl where R₁₀² and R₁₁² are independently hydrogen or C 1-4 alkyl. Preferably R₆⁴ is -CO(CH₂)₄ NR₁₀² R₁₁² where R₁₀² and R₁₁² are as defined. The invention further provides novel compounds within formula (I). Where compounds of formula (I) can exist in more than one stereoisomeric form, the invention extends to each of these forms and to mixtures thereof. Compounds of formula (I) described in EP-0167901 and EP-0213696 useful in the invention include: 6-Oxo-10-[2-(3-nitrobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole 6-Oxo-10-[2-(3-aminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole 6-Oxo-10-[2-(5-[3,5-dimethyl-piperidyl-(1)]valeryl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole 10-[2-(5-[3,5-Dimethyl-piperidyl-(1)]valeryl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole 10-[2-(5-Dimethylaminovaleryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole 10-[2-(5-[Piperidyl-(1)]valeryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole 10-[2-(5-[Pyrrolidinyl-(1)]valeryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole 10-[2-(5-[Morpholinyl-(1)]valeryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole 6-Oxo-10-[2-(3-piperidinobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole 6-Oxo-10-[2-(3-diisopropylaminobenzoyl)aminoethyl]-6,7, 8,9-tetrahydropyrido[1,2-a]indole 6-Oxo-10-[2-(3-pyrrolidinobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole 6-Oxo-[2-benzoylaminoethyl]-6,7,8,9,-tetrahydropyrido [1,2-a]indole 6-Oxo-10-[2-(3-dimethylaminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole 2-Methyl-6-oxo-10-[2-benzoylaminoethyl]-6,7,8,9-tetrahydropyrido [1,2-a]indole. Compounds D1 and D2 described hereinafter are also useful in the present invention. A process for the preparation of a compound of formula (I), or a pharmaceutically acceptable salt thereof comprises the conversion of a compound of formula (V): wherein R₁, R₄ and R₅ are as defined in formula (I) and Y is a group convertible to CH₂NR₆′R₇′ where R₆′ is R₆ as defined in formula (I) or a group convertible thereto, and R₇′ is an amino protecting group or R₇ as defined in formula (I), into a compound formula (Va): and thereafter, optionally and as necessary, converting R₆′ when other than R₆ into R₆, removing any R₇′ amino protecting group, interconverting R₆ and/or R₇ to other R₆ or R₇, reducing the R₂/R₃ bond and/or, when R₄/R₅ is oxo, reducing the oxo group to give a compound wherein R₄ and R₅ are both hydrogen and/or forming a pharmaceutically acceptable salt. Y may be a conventional amine precursor. Suitable examples include CN, COQ where Q is H or a leaving group such as halo, C 1-4 alkoxy or carboxylic acyloxy, and CH₂L where L is CON₃, N₃, NO₂ or X where X is a leaving group such as hydroxy, halo, C 1-4 alkoxy, C 1-4 alkanoyloxy, C 1-4 alkoxycarbonyloxy, tosyloxy or mesyloxy. The reaction converting the compound of formula (V) into that of formula (Va) may be carried out under the conventional conditions appropriate to the particular group Y in formula (V). Thus, when Y is CH₂CON₃, the conversion is a Curtius degradation carried out conventionally, by heating in dry inert solvent, such as benzene, and then subsequent hydrolysis of the thus formed isocyanate under acid conditions. When Y is CN, the conversion is a reduction to the primary amine, for example with a reducing agent such as diborane or LiAlH₄ at elevated temperature and in an inert solvent such as tetrahydrofuran, or with hydrogen over Raney nickel in the presence of ammonia at ambient temperature in a polar solvent such as methanol. When Y is CHO, the conversion is a condensation with hydroxylamine followed by reduction of the thus formed oxime over a metallic catalyst, or is a reductive amination with a primary or secondary amine using a reducing agent such as NaBH₃CN in a polar solvent such as CH₂Cl₂/CH₃OH at elevated temperature. Alternatively the intermediate imine may be prepared in a non polar solvent such as benzene in the presence of an acid catalyst e.g. p-toluenesulphonic acid and reduced with a reducing agent such as NaBH₄. When Y is COQ where Q is a leaving group, the conversion is a nucleophilic substitution by ammonia or a primary or secondary amine under conventional conditions appropriate for leaving group Q, followed by reduction of the resulting amide with e.g. LiAlH₄ in an inert solvent such as tetrahydrofuran at elevated temperature followed by work up. For example, when Q is halo such as chloro, the nucleophilic substitution may be carried out at ambient or lower temperature in the presence of an acid acceptor such as triethylamine in a polar solvent such as CH₂Cl₂, followed by work up to give the amide which may be reduced as just described. When Y is CH₂N₃, the conversion is a reduction of the azide to the primary amine with e.g. hydrogen over a metallic catalyst. When Y is CH₂NO₂, the conversion is a reduction of the nitro group to the primary amine with a reducing agent such as LiAlH₄, or hydrogen over Raney nickel or Pd/C catalyst in a polar solvent such as ethanol. When Y is CH₂X, the conversion is a nucleophilic substitution by ammonia or a primary or secondary amine or azide ion, under conventional conditions appropriate for the leaving group X. Thus, when X is hydroxy, it is first converted into a good leaving group such as mesylate or tosylate (using mesyl or tosyl chloride respectively) or chloride (using SOCl₃). The nucleophilic substitution may be carried out at elevated temperature in a polar solvent such as acetonitrile in the presence of an acid acceptor such as diisopropyl ethylamine. Alternatively, the leaving group may be substituted by nitrile to yield a compound of formula (V) where Y=CH₂CN. Hydrolysis and conversion by conventional methods yields a compound where Y=CH₂CON₃ via the acid as described hereinafter. Suitable examples of R₆′ include hydrogen, an amino protecting group and R₆ with any amino substituent on a phenyl moiety protected. In the resulting compound of formula (Va) in the case where R₆′ or R₇′ is an amino protecting group such as C 1-6 alkoxy carbonyl, aryloxycarbonyl, C 1-6 alkanoyl or phenyl C 1-7 alkanoyl, the protecting group may be removed by conventional procedures. Alternatively, R₇′ alkanoyl may be converted directly to alkyl or phenyl alkyl R₇ (as appropriate) by reduction, e.g. with LiAlH₄ and AlCl₃. When R₆′ is an R₆ group with a protected amino moiety, again the protecting group may be removed conventionally or the protected R₆ be converted to the desired R₆ group by reduction as in the preceding paragraph The conversion of any R₆′ amino protecting group to R₆ via the R₆′ hydrogen intermediate or the conversion of R₆′ hydrogen to R₆, may be carried out by conventional amine acylation. The interconversion of an R₇ hydrogen atom may be carried out by conventional amine alkylation or, more preferably, by acylation followed by reduction of the amide, or by reductive alkylation. Acylation may be carried out using the appropriate acyl chloride or anhydride and, if necessary, the subsequent reduction of the resulting amide with LiAlH₄ in the presence of AlCl₃. The reductive alkylation procedure is preferably carried out by heating with the aldehyde or ketone in an organic acid, such as acetic acid, then reducing the product in situ using an alkaline borohydride such as sodium borohydride or cyanoborohydride. The reaction can also be carried out in an alcohol, in which case the reduction can be carried out either chemically, for example with a borane such as trimethylammoniumborane or an alkaline borohydride or with hydrogen in the presence of a catalyst such as Raney nickel. It is also possible to use an aprotic solvent, for example an aromatic solvent such as benzene or toluene, the water formed being eliminated either at room temperature by means of a drying-agent or under reflux heating of the solvent by means of a Dean-Stark water-separator; the reduction can then be expediently carried out with hydrogen in the presence of a catalyst such as palladiated carbon or platinum oxide. These methods may be subject to certain limitations, depending on the nature of the aldehyde or ketone used. It is also possible to use a more universal method. For example, the R₇ hydrogen compound and the aldehyde or ketone to be condensed are dissolved in a mixture of solvents which can advantageously be a methanol-dichloromethane mixture in the presence of a complex reducing agent such as quaternary ammonium cyanoborohydride or, more simply, an alkaline cyanoborohydride solubilised by a phase-transfer agent, for example sodium cyanoborohydride and aliquat® 336 (Cf. Hutchins, R.O. and Markowitz, M., Journal of Organic Chemistry 1981, 46 , pp.3571-3574). The acylation may introduce the required moiety NR₁₀R₁₁ in the alkanoyl substituent R₆ directly, or alternatively by way of an amine precursor Y¹ which is convertible to CH₂ NR₁₀′ R₁₁′ (where R₁₀′ and R₁₁′ are R₁₀ and R₁₁ or groups convertible thereto) analogously to the conversion of the group Y in the compound of formula (V). For example, the amine precursor Y¹ may be of the formula CH₂X¹ where X¹ is a leaving group as defined for X above, such as halo e.g chloro which can be subsequently displaced by a compound HNR₁₀R₁₁. It will be appreciated that compounds of formula (I) wherein R₆ is substituted phenyl C 1-7 alkanoyl may be interconverted by conventional procedures including aromatic substituents. For example a compound of formula (I) wherein R₆ is benzoyl substituted by amino may be prepared from a compound wherein R₆ is benzoyl substituted by nitro, by catalytic reduction, for example in the presence of Raney nickel, or Pd/C and trifluoroacetic acid. A compound of formula (I) wherein R₆ is benzoyl substituted by substituted amino may be prepared from the corresponding amine by conventional procedures. Thus when R₈ or R₉ is an alkyl group, conventional amine alkylation may be employed. The reduction of the R₂/R₃ bond may be carried out conventionally by the use of an alkaline borohydride in a polar aprotic solvent such as dimethylsulphoxide or by nitromethane in the presence of a strong organic acid such as methanesulphonic acid or in pure trifluoroacetic acid. Alternatively the bond may be reduced catalytically with hydrogen over platinum oxide catalyst in a solvent permitting protonation of the indolic nitrogen, such as ethanol containing fluoroboric acid or acetic acid containing trifluoroacetic acid. When R₄ and R₅ together form an oxo group, compounds wherein R₄ and R₅ are both hydrogen may be prepared by reduction of the R₄/R₅ oxo group in formula (I) using a mixed hydride complexed with a Lewis acid, for example, the complex aluminium lithium aluminium chloride hydride in an inert solvent such as diethyl ether. When an R₇ group other than hydrogen is introduced initially by acylation to give the amide, simultaneous reduction of the R₄/R₅ oxo group and the amide moiety may be effected by appropriate choice of reducing agent, for example the mixed hydride complexed with a Lewis acid just described. When R₂ and R₃ together form a bond and R₄ and R₅ together form an oxo group, simultaneous reduction of the double bond and the oxo group may be effected by the use of an alkaline borohydride as described above for the reduction of an R₂/R₃ bond. It will be appreciated that these conversions may take place in any desired or necessary order. It will also be appreciated that conversions involving reduction should, preferably be carried out prior to the introduction of R₆ so as to avoid reduction of the amide. Pharmaceutically acceptable salts of the compounds of formula (I) may be formed conventionally by reaction with the appropriate acid such as described above under formula (I). The invention also provides a process for the preparation of novel compounds of formula (I), or a pharmaceutically acceptable salt thereof which process comprises the conversion of the compound of formula (V) as hereinbefore defined to the compound of formula (Va) as hereinbefore defined and thereafter, optionally and as necessary, converting R₆′ when other than R₆ into R₆, removing any R₇′ amino protecting group, interconverting R₆ and/or R₇ to other R₆ or R₇, reducing the R₂/R₃ bond and/or, when R₄/R₅ is oxo, reducing the oxo group to give a compound wherein R₄ and R₅ are both hydrogen and/or forming a pharmaceutically acceptable salt. Compounds of formula (V) in which Y is CH₂CON₃ may be prepared by the formation of the acid chloride followed by reaction of azide ion on an acid of formula (VI): This method is described in J. Am. Chem. Soc. 1981, 103 , 6990-6992. Acids of formula (VI) are known or may be prepared by conventional methods. For example, a phenylhydrazine is condensed with 4-oxoazelaic acid (ref. Von Pechmann et. al. Berichte 1904, 37 , p 3816). The hydrazone thus obtained is subjected to a Fischer cyclisation to give the acid of formula (VI). Compounds of formula (V) in which R₄ and R₅ are both hydrogen may be prepared by the reaction of a compound of formula (VII): with (i) ClCOCOR₁₃, where R₁₃ is alkoxy such as ethoxy or halo such as chloro, followed by reduction with LiAlH₄ to give a compound of formula (V) where Y is -CH₂OH which may subsequently be reacted with azide ion to give the corresponding compound where Y is -CH₂ N₃; (ii) CH₂=CH-R₁₄, where R₁₄ is a 1-carbonyl containing group or cyano, under basic conditions, followed by hydrolysis and reaction on the resulting acid group by azide ion as described above, to give a compound of formula (V) where Y is -CH₂CON₃; (iii) formaldehyde in the presence of dimethylamine followed by reaction of cyanide ion on the resulting tertiary amine, if necessary after quaternization, to give a compound of formula (V) where Y is -CN; (iv) CH₂=CHNO₂ under basic conditions to give a compound of formula (V) where Y is CH₂NO₂. Compounds of formula (VII) can be prepared according to Hans Zimmer, J. Heterocylic Chemistry 21 , 623(1984). Compounds of formula (V) in which Y is CHO may be prepared from the corresponding compound in which Y is CN by a variety conventional procedures such as, for example, reaction with diisobutylaluminium hydride. Compounds of formula (V) in which Y is COQ where Q is a leaving group may be prepared from the corresponding compound in which Y is CN by, for example, hydrolysis under acid conditions of the nitrile to give the corresponding acid, followed by conversion of the hydroxyl group to a leaving group Q such as chloro with a chlorinating agent such as oxalyl chloride. Interconversion of leaving groups Q may be carried out conventionally. Compounds of formula (V) in which R₄ and R₅ are both hydrogen and Y is-CH₂CN, may alternatively be prepared by homologation and reduction of a compound of formula (VIII): prepared according to D.N. Reinhoudt et al., Tetrahedron Letters 26 (5) 1985, 685-8. The nitrile is first reduced to the amine which is quaternised and reacted with cyanide ion to give the relevant compound of formula (V). In the formulae (VI),(VII) and (VIII) above, R₁ is as defined in formula (I). The following examples and pharmacological data illustrate the invention and the following descriptions illustrate the preparation of intermediates thereto. Description 1 10-[2-(4-Nitrobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (D1) A solution of 10g p-nitrobenzoyl chloride in 50ml of chloroform was added dropwise to a suspension of 10-(2-aminoethyl)-6,7,8,9-tetrahydropyrido[1,2-a]indole hydrochloride (E19 of EP-0167901) and 25ml triethylamine in 300ml chloroform. The mixture was left to stand for 2 hours at room temperature, then shaken with citric acid solution, sodium carbonate solution and brine, dried and evaporated. Crystallisation from diisopropyl ether yielded 13.2g, m.p: 184 - 5°C. Description 2 10-[2-(4-Aminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole hydrochloride (D2) Compound D1 was hydrogenated at room temperature at a pressure of 4 bar for 24 hours in trifluoroacetic acid in the presence of 1g Pd/C. The catalyst was filtered off, the solution concentrated, taken up in methylene chloride, shaken with sodium carbonate solution, dried, evaporated and the amine acidified with ethanol/HCl giving 9.6g product. m.p: 210°C. dec. Nmr (DMSO D6) δ = 1.7-2.3 [4]m; 4 [2]tr, J=6Hz; 6.9-8 [8]m. Description 3 10-[2-(4-Chloro-1-oxobutyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole(D3) D3 was prepared analogously to D3 in EP-0213696 from 6-oxo-10-(2-aminoethyl)-6,7,8,9-tetrahydropyrido[1,2-a]indole (compound D4 of EP-0167901) and 4-chlorobutyric acid chloride. m.p: 127°C. NMR (CDCl₃) δ = 8.45 [1]m; 7.35 [3]m; 5.88 [1]m; 3.55 [4]m; 2.78 [6]m; 2.15 [6]m. Description 4 10-[2-(6-Bromo-1-oxohexyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole(D4) Compound D4 was prepared analogously to D3 from 6-oxo-10-(2-aminoethyl)-6,7,8,9-tetrahydropyrido [1,2-a]indole (compound D4 of EP-0167901) and 6-bromohexanoic acid chloride. Yield: 34% m.p: 110 - 111°C Description 5 10-[2-[6-Bromo-1-oxohexyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole(D5) To the cooled mixture of 42.8g (0.2 mole) 10-(2-aminoethyl)-6,7,8,9-tetrahydropyrido[1,2-a]indole (E19 of EP-0167901) and 20.2g (0.2 mole) triethylamine, a solution of 42.7g (0.2 mole) 6-bromohexanoic acid chloride in 400ml chloroform was added dropwise. The temperature was adjusted to be between -10°C and +5°C. After the addition was complete, the reaction mixture was stirred at the above temperature for ½ hour, and then poured into crushed ice. The layers were separated and the organic phase washed with water and dried. The solvent was evaporated and the residue crystallised from ethyl acetate. Yield: 46.2g, 59% m.p: 118 - 119°C. Description 6 to 8 The compounds were prepared by an analogous procedure to that of Description 5: 10-[2-(4-Chloro-1-oxobutyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole(D6) Yield: 80% m.p: 120°C. 10-[2-(3-Chloro-1-oxopropyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole(D7) Yield: 75%. 10-[2-(2-Chloro-1-oxoethyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole(D8) Description 9 10-[2-N-Methylaminoethyl)-6,7,8,9-tetrahydropyrido[1,2-a]indole(D9) A mixture of 8.6g (0.038mole)6-oxo-10-(2-aminoethyl)-6,7,8,9-tetrahydropyrido[1,2-a]indole (compound D4 of EP-0167901) and 9.0g (0.12mole) ethyl formate was refluxed over 2 hours. The excess of ethyl formate was evaporated. The residue was dissolved in ethyl acetate, shaken with sodium carbonate solution, dried and evaporated yielding 9.5g (97% of theory) 6-oxo-10-(2-N-formylaminoethyl)-6,7,8,9-tetrahydropyrido[1,2-a]indole, which was dissolved in 100ml THF and added dropwise to a cooled suspension of 4.9g LiAlH₄ and 6.4g AlCl₃ in 100ml diethylether at - 10°C. The reaction mixture was stirred 2 hours at room temperature until the reduction was complete. The excess LiAlH₄/AlCl₃ was hydrolyzed with NaOH solution at - 5°C. The precipitate was filtered off and washed with ether. The filtrate was shaken with water and dilute HCl. The acidic extract was made alkaline with sodium carbonate solution and extracted with ether. The ether extract was dried and evaporated yielding 6.0g (71% of theory) yellow oily D9 base. calc.: C 78.95 H 8.77 N 12.28 found: C 78.97 H 9.06 N 12.04 The compound was converted to the hydrochloride. m.p: 252-254°C (decomp) Description 10 10-[2-(4-Chloro-1-oxobutyl-N-methylaminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole(D10) To a cooled mixture of 5.0g (0.022mole) D9 in 30ml chloroform was dropped 2.12g (0.022mole) triethylamine and a solution of 3.7g 4-chlorobutyric acid chloride in 10ml chloroform. After the addition was complete the reaction mixture was stirred 30 min. at room temperature and then poured onto crushed ice. The layers were separated and the organic phase was dried, filtered and evaporated, yelding 7g (96% of theory) oily D10. The compound crystallized by standing at room temperature. m.p: 76°C. Example 1 10-[2-(3-Nitrobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole semihydrate (E1) The synthesis is analogous to Description 1 4g m-nitrobenzoyl chloride. 4g amine hydrochloride E19 of EP-0167901. 8ml triethylamine. 140ml methylene chloride. Yield: 5.1g orange crystals containing 0.5mol water. m.p: 156°C. NMR (CDCl₃) δ = 1.7-2.3 [4]m; 2.7-3.2 [4]m; 3.5-3.9 [2]m; 4.15 [2]tr, J=6Hz; 6.3 [1]s broad exchange; 7.0-8.5 [8]m. Example 2 10-[2-(3-Aminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole hydrochloride (E2) 2.7g E1 was shaken in a hydrogenator overnight in 90ml methanol and 10ml trifluoroacetic acid and 0.3g 10% Pd on charcoal. The solution was filtered, made alkaline with sodium carbonate solution, extracted with methylene chloride and evaporated. The product was isolated as the hydrochloride. Yield: 2.8g. m.p: 174°C. NMR (DMSO d6) δ = 1.5-2.2 [4]m; 2.7-3.1 [4]m; 3.2-3.7 [2]m; 4.0 [2]tr, J=6Hz; 6.8-7.7 [8]m; 8.6 [1]tr, J=7Hz (exchange); 8.9 [3]s broad (exchange). Example 3 10-[2-(5-Dimethylamino-1-oxopentyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole (E3) 15g 6-Oxo-10-[2-(5-chlorovaleryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (D 3 of EP-0213696), 14.6ml diisopropylethylamine, 1g KI and 3.5g dimethylamine hydrochloride were dissolved in 100ml DMF and stirred for 48 hours at room-temperature. After further stirring for 7 hours at 40°C the reaction mixture was dissolved with water and extracted with ethyl acetate. After acid-base separation the product was crystallised from diisopropylether. Yield: 4g m.p: 115 - 116°C; NMR (CDCl₃) δ = 8.45 [1]m; 7.35 [3]m; 6.10 [1]m, broad; 3.50 [2]q, J=6.4Hz; 2.82 [6]m; 2.20 [12]m; 1.55 [4]m. Example 4 . 10-[2-(5-Piperidinyl-(1)-1-oxopentyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole hemihydrate (E4) 10g D3 of EP-0213696, 7.8ml piperidine, 1.5g KI and 5.1ml diisopropylethylamine were dissolved in 100ml acetonitrile and stirred for 17 hours at room temperature. After further stirring at 60°C for 12 hours the reaction mixture was diluted with 300ml water and extracted with CH₂Cl₂. After acid-base separation the product was crystallised from ethyl acetate. Yield: 8g m.p: 112°C NMR (CDCl₃) δ = 8.42 [1]m; 7.35 [3]m; 6.08 [1]m, broad; 3.50 [2]q, J=6.5Hz; 2.85 [6]m; 2.25 [10]m; 1.55 [10]m. calc.: C 71.26 H 8.47 N 10.39 found: C 70.84 H 8.30 N 10.42. Example 5 10-[2-(5-[3-Methylpiperidinyl-(1)]-1-oxopentyl) aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[l,2-a]indole (E5) 7g 6-Oxo-10-[2-(5-chlorovaleryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (D3 of EP-0213696), 4.5g 3-methylpiperidine, 0.5g KI and 5.1ml diisopropylethylamine were dissolved in 100ml DMF and heated for 12 hours at 55°C. After the addition of 300ml water and extraction with ethylacetate, the organic layer was extracted with citric acid. The acidic phase was made alkaline with sodium carbonate and extracted with CH₂Cl₂. The crude product was purified by column chromatography (CH₂Cl₂) and crystallised from ethyl acetate/ether. Yield: 5.2g m.p: 103-104°C NMR (CDCl₃) δ = 8.47 [1]m; 7.30 [3]m; 6.00 [1]m; 3.48 [2]q, J=6.3Hz; 2.80 [8]m; 2.15 [7]m; 1.55 [10]m; 0.80 [3]d, J=6Hz. calc.: C 73.31 H 8.61 N 10.26 found: C 73.76 H 8.64 N 10.26. Example 6 10-[2-(4-[3,5-Dimethylpiperidinyl-(1)]-1-oxobutyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido [1,2-a]indole hydrochloride hydrate (E6) 10g D3, 0.5g KI and 16ml 3,5-dimethylpiperidine were dissolved in 100ml acetonitrile and stirred for 28 hours at room temperature. Then the solvent was evaporated and the product purified by column chromatography (CH₂Cl₂). The compound was converted to the hydrochloride and crystallised from ethyl acetate. Yield: 3.7g m.p: 126°C. NMR (d₆-DMSO) δ = 10.85 [1]s, broad; 8.25 [2]m; 7.60 [1]m; 7.30 [2] m; 3.55-1.50 [24]m; 0.90 [6]d, J=6Hz. calc.: C 64.71 H 8.25 N 9.05 Cl 7.64 found: C 64.67 H 8.10 N 9.25 Cl 7.72. Example 7 10-[2-(4-[3,5-Dimethylpiperidinyl-(1)]-1-oxobutyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole hydrochloride (E7) 1g LiAlH₄ were suspended in 100ml ether/THF, cooled to -15°C and 2.1g AlCl₃ were added in small portions. 6.5g E6 were dissolved in 50ml THF and added dropwise to the reaction mixture. After 30 minutes 2.5M NaOH was added with caution until the solution was alkaline. The precipitate was filtered off and carefully washed with methanol. The filtrate was evaporated and the crude product purified by column chromatography (CH₂Cl₂/5%CH₃OH). The product crystallised as a hydrochloride from ethyl acetate. m.p: 183°C. NMR (d₆-DMSO) δ = 11.05 [1]s, broad; 8.28 [1]tr, broad; 7.55-6.85 [4]m; 4.00 [2]tr, J=4.5Hz; 3.40-1.50 [24]m; 0.85 [6]d, J=6Hz. Example 8 10-[2-(2-Phenylacetyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E8) 10.5g E19 of EP-0167901 were dissolved in 200ml CH₂Cl₂ and 10ml triethylamine were added. Then 7.73g phenylacetic acid chloride were added dropwise to the mixture. After stirring for 2 hr the reaction mixture was washed with dilute HCl-solution, with sodium carbonate and with brine. The organic layer was dried and evaporated. The product crystallised from diisopropylether. Yield: 8.9g m.p: 126°C NMR (DMSO-d₆) δ = 7.24 [9]m; 5.42 [1]s, broad; 4.00 [2]tr, J=6.3Hz; 4.47 [4]m; 2.75 [4]m; 1.92 [4]m. calc.: C 79.48 H 7.28 N 8.43 found: C 79.20 H 7.31 N 8.42. Example 9 10-[2-(4-Dimethylaminobenzylcarbonyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E9) (a) 4-Dimethylaminophenylacetic acid: 23g 4-Aminophenylacetic acid were dissolved in 250ml acetonitrile and 160ml formaldehyde (35% in water) were added. After cooling to 0°C, 40g NaBH₃CN were added to the mixture, followed by 20ml acetic acid added dropwise. After stirring for 2 hr at room temperature, again 20ml acetic acid were added dropwise to the reaction mixture. After 30 minutes it was poured into water and extracted with methylene chloride. The product was dried and the solvent evaporated. NMR (d₆-DMSO) δ = 8.99 [1]s; 7.20; 7.09; 6.79; 6.68 [4]-A-B-quartet; 3.53 [2]s; 2.92 [6]s. (b) The acid chloride of the product of (a) was prepared with SOCl₂ according to known methods. (c) Title Compound 7.2g E19 of EP-0167901 were dissolved in 100ml CH₂Cl₂. After addition of 14.6ml diisopropylethylamine, 5.15g 4-dimethylaminophenylacetic acid chloride from (b) in 20ml CH₂Cl₂ were added dropwise to the mixture. After 30 minutes the solution was washed with citric acid and with sodium carbonate. The solvent was evaporated and the compound purified by column chromatography (CH₂Cl₂). The product crystallised from ethyl acetate. m.p: 141°C NMR (CDCl₃) δ = 7.53-6.47 [8]m; 5.48 [1]s,broad; 3.98 [2]tr,J=6Hz; 3.45 [4]m; 2.80 [10]m; 1.90 [4]m. calc.: C 76.77 H 7.78 N 11.19 found: C 77.17 H 7.87 N 11.52. Example 10 10-[2-(4-Dimethylaminobenzoyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole (E10) E10 was prepared analogously to E9 from 7g D4 of EP-0167901, 11.2ml diisopropylethylamine and 4.5g 4-dimethylaminobenzoic acid chloride. The product was crystallised from isopropanol/ethyl acetate. Yield: 6.2g m.p: 200°C NMR (CDCl₃) δ = 8.45 [1]m; 7.45 [5]m; 6.62 [2]m; 6.13 [1]m; 3.66 [2]m; 2.80 [12]m; 2.00 [2]m. calc.: C 73.58 H 6.71 N 11.19 found: C 73.63 H 6.67 N 11.07. Example 11 10-[2-(4-Dimethylaminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole hydrochloride hemihydrate (E11) 5g E19 of EP-0167901 were dissolved in 100ml CH₂Cl₂ and 10ml diisopropylethylamine were added followed by 4g 4-dimethylaminobenzoic acid chloride added dropwise. After 2 hours the solution was poured into water, extracted with CH₂Cl₂ and the organic layer was washed with sodium carbonate. The product was purified by column chromatography (CH₂Cl₂) and converted to the hydrochloride. The product crystallised from ethyl acetate. Yield: 1.5g m.p: 207°C NMR (CDCl₃) (+D₂O - exchange) δ = 7.55 [3]m; 7.20 [3]m; 6.62 [2]m; 4.05 [2]m; 3.67 [2]tr, J=6.5Hz; 3.00 [10]m; 2.00 [4]m. Example 12 10-[2-(4-Aminobenzylcarbonyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole hydrochloride hemihydrate (E12) 6g E19 of EP-0167901 were dissolved in 100ml CH₂Cl₂. 12.2ml diisopropylethylamine and 4.3g aminophenylacetic acid chloride were added. The mixture was stirred for 1 hour and was worked up as in Example 11. The obtained hydrochloride crystallised from ethyl acetate. Yield: 1.3g m.p: 254°C NMR (d₆-DMSO) δ = 8.15 [1]m; 7.60-6.80 [8]; 4.00 [2]tr, J=6Hz; 3.42 [2]s; 3.20 [2]m; 2.75 [4]m; 1.88 [4]m. Example 13 10-[2-(4-Dimethylaminobenzylcarbonyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole (E13) a) 11g 4-Dimethylaminophenylacetic acid (see Example 9a) were dissolved in 100ml CH₂Cl₂. Then 10.8g carbonyldiimidazole were added. After 30 minutes the organic layer was washed with water, dried and evaporated. Yield: 12.5g (b) Title compound 15.7g (0.069 mol) D4 of EP-0167901 and 12.5g product of Example 13a were dissolved in CH₂Cl₂ and stirred for 3 hours at room temperature. The solvent was evaporated and the product purified by column chromatography (ether/2% CH₃OH). The product crystallised from ethyl acetate. Yield: 7.4g m.p: 146°C NMR (CDCl₃) δ = 8.45 [1]m; 7.30 [3]m; 6.78 [4], AB-quartet, J=8.8Hz, J=18Hz; 3.40 [4]m; 2.93 [6]s; 2.70 [6]tr, J=6.5Hz; 2.00 [2]m. Example 14 10-[2-(3-Phenylpropionyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]-indole (E14) Example 14 was prepared analogously to Example 8 from 15.3g E19 of EP-0167901, 15.4ml triethylamine and 12g 3-phenylpropionic acid chloride. The product crystallised from ether. m.p: 99°C NMR (DMSO-d₆) δ = 7.86 [1]m; 7.21 [9]m; 3.98 [2]tr; 3.20 [2]m; 3.00-2.20 [8]m; 1.90 [4]m. calc.: C 79.73 H 7.57 N 8.09 found: C 80.16 H 7.62 N 8.02. Example 15 10-[2-(5-[3-Methylpiperidinyl-(1)]-1-oxopentyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole hydrochloride hemihydrate (E15) 2g 10-[2-(5-Chlorovaleryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (D6 of EP-0213696), 1.2g 3-methylpiperidine and 0.2g KI in 20ml DMF were heated at 55°C for 14 hours. The reaction mixture was then diluted with 200ml water and extracted with ethyl acetate. After acid/base separation with citric acid/sodium carbonate, the crude product was converted into the hydrochloride and crystallized from isopropanol/diisopropylether. m.p: 118°C (dec.) NMR (d₆-DMSO) δ = 10.65 [1]s, broad; 8.00 [1]s, broad; 7.55-6.85 (4)m; 4.00 [2]tr, J=5.5Hz; 3.55-2.55 [11]m; 2.30-1.30 [16]m; 0.85 [3]d, J=6Hz. Example 16 10-[2-(6-[N,N-Dimethylamino]-1-oxohexyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole (E16) 8.9g (0.022 mole) D4, 3.2g (0.44 mole) dimethylammonium chloride and 6g triethylamine were dissolved in 150ml N,N-dimethylformamide and heated for 6h at 90°C. The solvent was evaporated in vacuo and the residue extracted with 100ml chloroform and 100ml water. The organic layer was separated and dried. The solvent was evaporated and the residue crystallised from ethyl acetate. Yield: 0.7g m.p: 103°C Example 17 10-[2-(6-[3,5-Dimethylpiperidinyl-(1)]-1-oxohexyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole hydrochloride (E17) 4.05g (0.01 mole) D4, 1.7g (0.015 mole) 3,5-dimethylpiperidine and 1.5g (0.015 mole) triethylamine were dissolved in 50ml DMF and heated under stirring at 75°C for 2h. The solvent was evaporated and the residue was taken up in water/methylene chloride (150ml/150ml). The layers were separated. The organic layer was extracted with Na₂CO₃ solution and dried. The solvent was evaporated in vacuo and the residue purified by column chromatography over silica gel (CH₂Cl₂) and crystallized from ethyl acetate. Yield: 2.2g (50%) m.p: 120-121°C calc.: C 74.14 H 8.92 N 9.61 found: C 73.94 H 8.85 N 9.49. The base was converted to the hydrochloride salt by the addition of an equivalent amount of isopropanolic solution of HCl (0.1N). The product was crystallized from ethyl acetate. Yield: 2.1g m.p: 157-158°C (decomp.). Example 18 10-[2-(4-[2,4-Dimethylpyrrolidinyl-(1)]-1-oxobutyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole(E18) 2.2g (0.007 mole) D6 and 3.1g (0.028 mole) 2,4-dimethylpyrrolidine were heated to 60-70°C for 3 hours. The reaction mixture was thereafter diluted with 100ml ethyl acetate and extracted with water and a solution of citric acid. The layers were separated. The aqueous phase was made alkaline with Na₂CO₃ and extracted with ethyl acetate. The organic layer was separated, dried and evaporated. The residue was purified by column chromatography (SiO₂/CH₂Cl₂). Yield: 1.4g (52%) oily product. calc.: C 75.59 H 9.19 N 11.02 found: C 75.53 H 9.20 N 11.40 The compounds of Examples 19 and 20 were prepared by an analogous procedure to that of Example 18. Example 19 10-[2-(4-[2-Methylpiperidinyl-(1)]-1-oxobutyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E19) Example 20 10-[2-(4-[Morpholinyl-(1)]-1-oxobutyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E20) Yield: 43% m.p: 94°C calc.: C 71.5 H 8.40 N 11.38 found: C 71.4 H 8.40 N 11.85 Hydrochloride m.p: 177-179°C. Example 21 10-[2-(6-[N,N-Dimethylamino]-1-oxohexyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole hydrochloride hydrate (E21) 5.9g (0.015 mole) D5, 2.4g (0.03 mole) dimethylamine hydrochloride and 1.2g (0.03 mole) NaOH were dissolved in 80ml DMF and 3ml water. The reaction mixture was heated to 75°C for 2 hours. The solvent was evaporated and the residue purified by column chromatography on silica gel (CH₂Cl₂). Yield: 2.5g (33.5%) The compound was converted to the hydrochloride and crystallised from ethyl acetate/ethyl alcohol. Yield: 1.7g m.p: 116-118°C calc.: C 64.47 H 8.79 N 10.26 Cl 8.67 found: C 64.88 H 8.47 N 9.94 Cl 8.39. The compounds of Examples 22 to 25 were prepared by an analogous procedure to that of Example 21. Example 22 10-[2-(6-[3,5-Dimethylpiperidinyl-(1)]-1-oxohexyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E22) Yield: 69% m.p: 88-90°C calc.: C 76.60 H 9.69 N 9.93 found: C 76.55 H 9.67 N 9.87. Example 23 10-[2-(6-[2,6-Dimethylpiperidinyl-(1)-1-oxohexyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E23) Yield: 26% calc.: C 76.60 H 9.69 N 9.93 found: C 76.50 H 8.70 N 9.88. Example 24 10-[2-(6-[3-Methylpiperidinyl-(1)]-1-oxohexyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E24) Yield: 75% m.p: 99-100°C calc.: C 76.28 H 9.54 N 10.27 found: C 76.28 H 9.57 N 10.21. Example 25 10-[2-(6-Piperidinyl-(1)-1-oxohexyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole hydrochloride hydrate (E25) Yield: 70% m.p: 160-165% calc.: C 66.74 H 9.90 N 9.34 Cl 7.90 found: C 65.74 H 8.63 N 9.22 Cl 8.42. Example 26 10-[2-(3-[3,5-Dimethylpiperidinyl-(1)]-1-oxopropyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E26) Compound E26 was prepared from intermediate D7 and 3,5-dimethylpiperidine by an analogous procedure to that of Example 21. m.p: 136°C calc.: C 75.55 H 9.25 N 11.01 O 4.19 found: C 75.43 H 9.23 N 10.92 O 4.18 Hydrogensulphate m.p: 208°C Example 27 10-[2-(2-[3,5-Dimethylpiperidinyl-(1)]-1-oxoethyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E27) Compound E27 gas prepared from intermediate D8 and 3,5-dimethylpiperidine by an analogous procedure to that of Example 21. Yield: 67%, oil calc.: C 72.51 H 9.05 N 11.43 O 4.35 found: C 72.88 H 8.88 N 10.98 O 6.63 NMR (CDCl₃) δ = 8.2 [1]s broad (exch.); 7.4-7.6 [1]m; 6.9-9.3[3]m; 3.9-4.1 [2]t; 3.3-3.7 [2]q; 2.8-3.0 [4]t; 0.9-2.7 [16]m; 0.7-0.8 [6]d. Example 28 10-[2-(4-[2,5-Dimethylpyrrolidyl-(1)]-1-oxobutyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E28) The compound E28 was prepared from intermediate D6 and 2,5-dimethylpyrrolidine by an analogous procedure to that of Example 18. Yield 55% of theory. The compound was converted to hydrochloride which is amorphous and hygroscopic. calc.: C 66.13 H 8.73 N 9.64 Cl 8.15 found: C 66.04 H 8.66 N 9.40 Cl 7.92 Example 29 10-[2-(4-[3,5-Dimethylpiperidinyl-(1)]-1-oxobutyl)-N-methylaminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E29) 1.9g D10 and 2.6g 3,5-dimethylpiperidine was heated for 2 hours at 70°C. The reaction mixture was taken up in ethyl acetate and shaken with water and citric acid solution. The water phase was made alkaline with sodium carbonate solution and extracted with ethyl acetate. The organic extract was dried and evaporated yielding 1.4g (60% of theory) oily E29 base. calc.: C 76.28 H 9.54 N 10.27 found: C 75.05 H 9.59 N 10.44 Example 30 10-[2-(4-[2,4-Dimethylpyrrolidinyl-(1)]-1-oxobutyl)-N-methylaminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole (E30) The compound E 30 was prepared from intermediate D10 and 2,4-dimethylpyrrolidine by an analogous procedure to that of Example 29. Yield 44% of theory. calc.: C 75.94 H 9.37 N 10.63 found: C 75.79 H 9.16 N 10.65 Example 31 10-[2-(3-Phenylpropionyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole (E31) 10.6g (409mM) D 4 (EP 0167901) HCl were suspended in 200ml CH₂Cl₂ and, at 0°C, 10ml 3-phenylpropionylchloride were added. Thereafter, the mixture was cooled to -20°C and 20ml diisopropylethylamine were added dropwise. The mixture was allowed to warm to room temperature and shaken three times, each with a 10% solution of citric acid and sodium carbonate. The organic phase was dried with Na₂SO₄, filtered and evaporated. The residue was heated with charcoal in 400ml methanol and concentrated to about 150ml and, after cooling, 10.8g of white crystals were obtained. m.p: 109°C NMR (CDCl₃) δ= 1.8 - 2.2 [2] m; 2.3 - 2.6 [2] m; 2.6 -3.1 [8] m; 3.39 [2] q J = 7 Hz (after exchange tr.); 5.55 [1] s broad, exchange; 7.0 - 7.6 [8] m; 8.4 - 8.6 [1] m. Pharmacological Data 1. Triethyltin-induced cerebral oedema in the rat. The cerebral oedema is induced by oral administrations repeated for 5 consecutive days - one administration per day - of triethyltin chloride at a dose of 2 mg/kg. The study substances are also administered orally twice daily as aqueous solution or suspension at a dose of 1ml/100g body-weight; these administrations are given during the 5 days of intoxication with tin. Three groups of 10 male specific pathogen-free (SPF) Wistar rats of 280 ± 10g body-weight are used for each compound studied: 1 control group 1 group intoxicated with triethyltin 1 group intoxicated with triethyltin and treated with the studied compound. The rats are killed on the evening of the fifth day; the brain is removed, weighed fresh and after desiccation to constant weight and the water content of each brain is calculated: [H₂O] = fresh weight - dry weight. The following are then calculated: the mean water content (M ± Sm%) of each group; the protection index P due to the administered compound: The results are shown in Table 1. Compound No. Triethyltin-induced cerebral oedema % protection at dose administered (mg/kg p.o.) 2 x 5 2 x 12.5 2 x 25 Significance E7 65 b E8 50 c E9 77 95 a E10 35.5 c E17 47.3 b E18 41.4 c Significance: a: p<0.01 b: p<0.05 c: p = 0.05 2. The Gerbil Ischaemic Deficit Passive Avoidance Test . Mongolian gerbils were conditioned to avoid entering a dark compartment by means of a footshock (maximally 50V, 2s duration) received when entering from the light section of a two compartment box. Recollection of the footshock was examined 24h later by replacing the gerbils in the two compartment box and measuring the recall latency, the time taken to re-enter the dark compartment. Effect of test compound on recall latency in the gerbil following transient forebrain ischaemia. (a) Animal Preparation A learning or memory deficit was induced in the gerbils by a transient (5min) bilateral carotid artery ligation, performed 24h prior to conditioning, under light hexobarbital anaesthesia. (b) Measurement Compounds, being examined for an effect on learning or memory in gerbils which had undergone carotid occlusion, were administered seven times during the experiment. The initial administration was during the period of forebrain ischaemia, the third and seventh administrations were 10min prior to conditioning and recall testing, respectively, and the remainder were given at intermediate time points. Results were expressed as percentage of animals which had a long recall latency (>60s). A long recall latency indicates good information acquisition or retrival. (c) Results The results for test compounds are shown in Table 2. As can be seen in Table 2, transient cerebral ischaemia impairs the recollection of the footstock in gerbils. The test compounds significantly increased the percentage of animals with long recall latencies. The above results show that the test compounds improve data acquisition or retrieval in the gerbil following transient forebrain ischaemia and demonstrate that the compounds of the invention are of potential use in the treatment of cerebral vascular and neuronal degenerative disorders associated with learning, memory and cognitive dysfunctions including cerebral senility, multi-infarct dementia and senile dementia of the Alzheimer type.

Claims: Claims for the following Contracting States : AT, BE, CH, DE, FR, GB, GR, IT, LI, LU, NL, SE A pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof: wherein: R₁ is hydrogen, C 1-6 alkyl, C 1-6 alkoxy or halogen; R₂ and R₃ are both hydrogen or together represent a bond; R₄ is hydrogen and R₅ is hydrogen or R₄ and R₅ together represent an oxo group; R₆ is phenyl C 1-7 alkanoyl in which the phenyl moiety is optionally substituted by one or two of halogen, nitro, meta - or para -methoxy, methyl or NR₈R₉ wherein R₈ and R₉ are independently hydrogen or C 1-6 alkyl or R₈ and R₉ together are C 2-6 polymethylene, or 3,4-disubstituted by methylenedioxy or ethylenedioxy; or C 1-7 alkanoyl substituted by NR₁₀R₁₁ where R₁₀ and R₁₁ are independently hydrogen or C 1-4 alkyl or together are C 3-7 polymethylene optionally containing a further hetereoatom which is oxygen, sulphur or nitrogen substituted by R₁₂ where R₁₂ is hydrogen, C 1-4 alkyl or benzyl, and optionally substituted by one or two C 1-4 alkyl, C 2-5 alkanoyl, C 1-4 alkoxycarbonyl, aminocarbonyl optionally substituted by one or two C 1-6 alkyl groups or by a benzyl group, cyano, phenyl or benzyl and wherein any phenyl or benzyl group is optionally substituted in the phenyl ring by one or two halo, CF₃, C 1-4 alkyl, C 1-4 alkoxy, cyano or nitro groups; and R₇ is hydrogen or C 1-4 alkyl; and a pharmaceutically acceptable carrier. A pharmaceutical composition according to claim 1, wherein R₁ is hydrogen and R₂ and R₃ represent a bond. A pharmaceutical composition according to claim 1 or 2, wherein R₄ and R₅ represent hydrogen. A pharmaceutical composition according to any preceding claim, wherein R₇ represents hydrogen. A pharmaceutical composition according to any preceding claim, wherein R₆ is benzoyl, phenacetyl, 3-phenylpropionyl, or 2-methyl-2-phenylacetyl optionally monosubstituted in the phenyl moiety by NR₈R₉, or C₃₋₇ alkanoyl substituted by NR₁₀R₁₁; wherein R₈, R₉, R₁₀ and R₁₁ are as defined in claim 1. A pharmaceutical composition according to claim 5 wherein R₁₀ and R₁₁ together are C 3-7 polymethylene optionally containing a further heteroatom which is oxygen, sulphur or nitrogen substituted by R₁₂ where R₁₂ is hydrogen, C 1-4 alkyl or benzyl, and optionally substituted by one one or two C 1-4 alkyl groups. A pharmaceutical composition according to claim 6, wherein NR₁₀R₁₁ comprises 5 to 7 ring atoms. A pharmaceutical composition according to claim 7, wherein NR₁₀R₁₁ is selected from 1-piperidyl, 2-methyl-1-piperidyl, 3-methyl-1-piperidyl, 3,5-dimethyl-1-piperidyl, 2,6-dimethyl-1-piperidyl, 2,5-dimethyl-1-pyrrolidyl, 2,4-dimethyl-1-pyrrolidyl and 1-morpholinyl. A pharmaceutical composition according to any of claims 5 to 8, wherein R₆ is C₃₋₅ alkanoyl substituted by NR₁₀R₁₁, wherein R₁₀ and R₁₁ are as defined in any one of claims 5 to 8. A compound of formula (I) as defined in any of claims 1 to 9, other than: 6-oxo-10-[2-(3-nitrobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-10-[2-(3-aminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-10-[2-(5-[3,5-dimethyl-piperidyl-(1)]valeryl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-[3,5-dimethyl-piperidyl-(1)]valeryl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-dimethylaminovaleryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-[piperidyl-(1)]valeryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-[pyrrolidinyl-(1)]valeryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-[morpholinyl-(1)]valeryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-10-[2-(3-piperidinobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-10-[2-(3-diisopropylaminobenzoyl)aminoethyl]-6,7, 8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-10-[2-(3-pyrrolidinobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-[2-benzoylaminoethyl]-6,7,8,9,-tetrahydropyrido [1,2-a]indole, 6-oxo-10-[2-(3-dimethylaminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 2-methyl-6-oxo-10-[2-benzoylaminoethyl]-6,7,8,9-tetrahydropyrido [1,2-a]indole, 10-[2-(4-nitrobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole and 10-[2-(4-aminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole. 10-[2-(3-Nitrobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(3-aminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-dimethylamino-1-oxopentyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-piperidinyl-(1)-1-oxopentyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-[3-methylpiperidinyl-(1)]-1-oxopentyl) aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a] indole, 10-[2-(4-[3,5-dimethylpiperidinyl-(1)]-1-oxo-butyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido [1,2-a]indole, 10-[2-(4-[3,5-dimethylpiperidinyl-(1)]-1-oxobutyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(2-phenylacetyl)aminoethyl]-6,7,8,9-tetrahydro-py rido[1,2-a]indole, 10-[2-(4-dimethylaminobenzylcarbonyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(4-dimethylaminobenzoyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(4-dimethylaminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(4-aminobenzylcarbonyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(4-dimethylaminobenzylcarbonyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(3-phenylpropionyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]-indole, 10-[2-(5-[3-methylpiperidinyl-(1)]-1-oxopentyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(6-[N,N-dimethylamino]-1-oxohexyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(6-[3,5-dimethylpiperidinyl-(1)]-1-oxohexyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(4-[2,4-dimethylpyrrolidinyl-(1)]-1-oxobutyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(4-[2-methylpiperidinyl-(1)]-1-oxobutyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(4-[morpholinyl-(1)]-1-oxobutyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(6-[N,N-dimethylamino]-1-oxohexyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(6-[3,5-dimethylpiperidinyl-(1)]-1-oxohexyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(6-[2,6-dimethylpiperidinyl-(1)]-1-oxohexyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(6-[3-methylpiperidinyl-(1)]-1-oxohexyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(6-piperidinyl-(1)-1-oxohexyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(3-[3,5-dimethylpiperidinyl-(1)]-1-oxopropyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(2-[3,5-dimethylpiperidinyl-(1)]-1-oxoethyl)amino ethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(4-[2,5-dimethylpyrrolidyl-(1)]-1-oxobutyl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(4-[3,5-dimethylpiperidinyl-(1)]-1-oxobutyl)-N-methylaminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a] indole, 10-[2-(4-[2,4-dimethylpyrrolidinyl-(1)]-1-oxobutyl)-N-methylaminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole or 10-[2-(3-phenylpropionyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole, or a pharmaceutically acceptable salt of any of the foregoing compounds. A process for preparing a compound as defined in claim 10, which process comprises the conversion of a compound of formula (V): wherein R₁, R₄ and R₅ are as defined in claim 10 and Y is a group convertible to CH₂NR₆′R₇′ where R₆′ is R₆ as defined in claim 10 or a group convertible thereto, and R₇′ is an amino protecting group or R₇ as defined in claim 10, into a compound of formula (Va): and thereafter, optionally and as necessary, converting R₆′when other than R₆ into R₆, removing any R₇′amino protecting group, interconverting R₆ and/or R₇ to other R₆ or R₇, reducing the R₂/R₃ bond and/or, when R₄/R₅ is oxo, reducing the oxo group to give a compound wherein R₄ and R₅ are both hydrogen and/or forming a pharmaceutically acceptable salt. A compound of formula (I) as defined in claim 1 or a pharmaceutically acceptable salt thereof, for use as an active therapeutic substance. A compound of formula (I) as defined in claim 1 or a pharmaceutically acceptable salt thereof, for use in the treatment of cerebral vascular and neuronal degenerative disorders associated with learning, memory and cognitive dysfunctions including cerebral senility, multi-infarct dementia and senile dementia of the Alzheimer type. Use of a compound of formula (I) as defined in claim 1 or a pharmaceutically acceptable salt thereof, for the preparation of a medicament for the treatment of cerebral vascular and neuronal degenerative disorders associated with learning, memory and cognitive dysfunctions including cerebral senility, multi-infarct dementia and senile dementia of the Alzheimer type. Claims for the following Contracting State : ES A process for preparing a compound of formula (I) or a pharmaceutically acceptable salt thereof: wherein: R₁ is hydrogen, C 1-6 alkyl, C 1-6 alkoxy or halogen; R₂ and R₃ are both hydrogen or together represent a bond; R₄ is hydrogen and R₅ is hydrogen or R₄ and R₅ together represent an oxo group; R₆ is phenyl C 1-7 alkanoyl in which the phenyl moiety is optionally substituted by one or two of halogen, nitro, meta - or para -methoxy, methyl or NR₈R₉ wherein R₈ and R₉ are independently hydrogen or C 1-6 alkyl or R₈ and R₉ together are C 2-6 polymethylene, or 3,4-disubstituted by methylenedioxy or ethylenedioxy; or C 1-7 alkanoyl substituted by NR₁₀R₁₁ where R₁₀ and R₁₁ are independently hydrogen or C 1-4 alkyl or together are C 3-7 polymethylene optionally containing a further hetereoatom which is oxygen, sulphur or nitrogen substituted by R₁₂ where R₁₂ is hydrogen, C 1-4 alkyl or benzyl, and optionally substituted by one or two C 1-4 alkyl, C 2-5 alkanoyl, C 1-4 alkoxycarbonyl, aminocarbonyl optionally substituted by one or two C 1-6 alkyl groups or by a benzyl group, cyano, phenyl or benzyl and wherein any phenyl or benzyl group is optionally substituted in the phenyl ring by one or two halo, CF₃, C 1-4 alkyl, C 1-4 alkoxy, cyano or nitro groups; and R₇ is hydrogen or C 1-4 alkyl; other than 6-oxo-10-[2-(3-nitrobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-10-[2-(3-aminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-10-[2-(5-[3,5-dimethyl-piperidyl-(1)]valeryl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-[3,5-dimethyl-piperidyl-(1)]valeryl) aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-dimethylaminovaleryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-[piperidyl-(1)]valeryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-[pyrrolidinyl-(1)]valeryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-[morpholinyl-(1)]valeryl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-10-[2-(3-piperidinobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-10-[2-(3-diisopropylaminobenzoyl)aminoethyl]-6,7, 8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-10-[2-(3-pyrrolidinobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 6-oxo-[2-benzoylaminoethyl]-6,7,8,9,-tetrahydropyrido [1,2-a]indole, 6-oxo-10-[2-(3-dimethylaminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 2-methyl-6-oxo-10-[2-benzoylaminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(4-nitrobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole and 10-[2-(4-aminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, which process comprises the conversion of a compound of formula (V): wherein R₁, R₄ and R₅ are as defined in claim 10 and Y is a group convertible to CH₂NR₆′R₇′ where R₆′ is R₆ as defined in formula (I) or a group convertible thereto, and R₇′ is an amino protecting group or R₇ as defined in formula (I), into a compound of formula (Va): and thereafter, optionally and as necessary, converting R₆′ when other than R₆ into R₆, removing any R₇′ amino protecting group, interconverting R₆ and/or R₇ to other R₆ or R₇, reducing the R₂/R₃ bond and/or, when R₄/R₅ is oxo, reducing the oxo group to give a compound wherein R₄ and R₅ are both hydrogen and/or forming a pharmaceutically acceptable salt. A process according to claim 1, wherein R₁ is hydrogen and R₂ and R₃ represent a bond. A process according to claim 1 or 2, wherein R₄ and R₅ represent hydrogen. A process according to any preceding claim, wherein R₇ represents hydrogen. A process according to any preceding claim, wherein R₆ is benzoyl, phenacetyl, 3-phenylpropionyl or 2-methyl-2-phenylacetyl optionally monosubstituted in the phenyl moiety by NR₈R₉, or C₃₋₇ alkanoyl substituted by NR₁₀R₁₁, wherein R₈, R₉, R₁₀ and R₁₁ are as defined in claim 1. A process according to claim 5 wherein R₁₀ and R₁₁ together are C₃₋₇ polymethylene optionally containing a further heteroatom which is oxygen, sulphur or nitrogen substituted by R₁₂ where R₁₂ is hydrogen, C₁₋₄ alkyl or benzyl, and optionally substituted by one one or two C₁₋₄ alkyl groups. A process according to claim 6, wherein NR₁₀R₁₁ comprises 5 to 7 ring atoms. A process according to claim 7, wherein NR₁₀R₁₁ is selected from 1-piperidyl, 2-methyl-1-piperidyl, 3-methyl-1-piperidyl, 3,5-dimethyl-1-piperidyl, 2,6-dimethyl-1-piperidyl, 2,5-dimethyl-1-pyrrolidyl, 2,4-dimethyl-1-pyrrolidyl and 1-morpholinyl. A process according to any of claims 5 to 8, wherein R₆ is C₃₋₅ alkanoyl substituted by NR₁₀R₁₁, wherein R₁₀ and R₁₁ are as defined in any of claims 5 to 8. A process according to claim 1 for preparing 10-[2-(3-nitrobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(3-aminobenzoyl)aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-dimethylamino-1-oxopentyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-piperidinyl-(1)-1-oxopentyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(5-[3-methylpiperidinyl-(1)]-1-oxopentyl) aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a] indole, 10-[2-(4-[3,5-dimethylpiperidinyl-(1)]-1-oxo-butyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido [1,2-a]indole, 10-[2-(4-[3,5-dimethylpiperidinyl-(1)]-1-oxobutyl)-aminoethyl]-6,7,8,9-tetrahydropyrido[1,2-a]indole, 10-[2-(3-phenylpropionyl)aminoethyl]-6-oxo-6,7,8,9-tetrahydropyrido[1,2-a]indole, or a pharmaceutically acceptable salt of any of the foregoing compounds. Use of a compound of formula (I) as defined in claim 1 or a pharmaceutically acceptable salt thereof, for the preparation of a medicament for the treatment of cerebral vascular and neuronal degenerative disorders associated with learning, memory and cognitive dysfunctions including cerebral senility, multi-infarct dementia and senile dementia of the Alzheimer type.

Inventors: HOELTJE, DAGMAR BEECHAM-WUELFING GMBH & CO KG., JOZIC, LJERKA BEECHAM-WUELFING GMBH & CO KG., THIELKE, DIETRICH BEECHAM-WUELFING GMBH & CO KG., Hoeltje, Dagmar Beecham-Wuelfing GmbH &amp; Co KG., Jozic, Ljerka Beecham-Wuelfing GmbH &amp; Co KG., Thielke, Dietrich Beecham-Wuelfing GmbH &amp; Co KG.
Applicants: BEECHAM - WUELFING GMBH & CO. KG
Application year: 1987
Main classification: A61K31
IPC codes: C07D471, A61K31