GB2157685A - Piperazine derivatives - Google Patents

Abstract

Compounds of the general formula <IMAGE> wherein X is C1-C6, straight chain saturaged or unsaturated hydrocarbyl group, the group R<4> and the group Y are situated in any position in this chain and wherein at least one of the hydrogen atoms in X can be a heavy isotope of hydrogen; R<4> is hydrogen or an alkyl, alkoxy, hydroxy, aryl, aryloxy, aralkyl, aralkoxy, aralkylamino, or morpholino group wherein the alkyl or aryl part of any one of said groups may be substituted by one or more halogeno groups; or R<4>, together with at least one carbon atom of the group X, forms a carbocyclic or heterocyclic ring of 5 to 6 ring atoms; Y is an acidic or related group giving rise to one or more electronegative sites in the group; or R<4>-X-Y represents a carboxylic acyl group; R is hydrogen or an alkyl, haloalkyl, aryl, haloaryl, aralkyl or haloaralkyl; R<1> is hydrogen or an alkyl, haloalkyl, aryl, haloaryl, aralkyl or haloaralkyl group; R<2>, R<3> and R<5> which may be the same or different is each hydrogen or an alkyl, hydroxy, alkoxy, carboxy, alkyloxycarbonyl, halo, aryl, haloaryl or aryloxycarbonyl group; or R<2> and R<3> together with the carbon atoms to which they are attached form a ring system or R<3> and R<4> together and/or R<3> and X together form one or more than one ring system, and physiologically acceptable salts thereof have activity in the central nervous system.

Description

1 GB 2 157 685 A 1

SPECIFICATION

Organic compounds This invention relates to new organic compounds and more particularly, new 4-substituted piperazine-2carboxylic acids of interest as agents influencing the central nervous system, their preparation, pharmaceutical compositions containing them and the compounds for use in methods of therapy practised on the human or animal body.

Various amino acids have recently become of interest following the discovery that they are able to influence the activity of certain receptor sites in the central nervous system and attention has been directed 10 to the identification of materials that will have specific action in relation to these receptor sites with a view of identifying compounds that can be used to control various involuntary muscular activity andlor mental and/or affective disorders resulting from central nervous system malfunction.

We have now found that certain 4-substituted piperazine-2-carboxylic acids, which is a type of structure not previously investigated in relation to such activity, do act as depressants of electrical activity at certain receptor sites of the central nervous system.

Accordingly, the present invention provides compounds of the general formula:

4 X Y 3 2 COOR 1 wherein X is a Cl-C6, preferably a Cl-C4 straight chain saturated or unsaturated hydrocarbyl group, the group R 4 and the group Y are situated in any position in this chain and wherein at least one of the hydrogen atoms 30 in X can be a heavy isotope of hydrogen.

The group R 4 is.hydrogen or an alkyl, alkoxy, hydroxy, aryl, aryloxy, aralkyl, aralkoxy, aralkylamino, or morpholino group wherein the alkyl or aryl part of any one of said groups may be substituted by one or mor 4 halogeno groups; or wherein R, together with at least one carbon atom of the group X forms a carbocyclic or heterocyclic ring of 5 to 6 ring atoms; Y is an acidic or related group giving rise to one or more electronegative sites in the group, usually:

0 11 -P-OR 6 Ila 40 1 Uhl or 0 45 Url- lib U or 50 0 11 - 2 - un- or lic 0 11 - 11 - un- lid 2 GB 2 157 685 A or 0 Hi - B - OW3 1 U lie 7 where R' and R, which may be the same or different, each is hydrogen or an alkyl, haloalkyl, aryl, haloary], aralkyl or haloaralkyl group; or wherein 2 R4-X-y 1 represents a carboxylic acyl group; R can represent hydrogen or an alkyl, haloalkyl, aryl, haloaryl, aralkyl or haloaralkyl residue; wherein R' is hydrogen or an alkyl, haloalky], ary], haloary], aralkyl or haloaralkyl group; wherein R', R' and R'which may be the same or different is each hydrogen or an alkyl, hydroxy, alkoxy, 20 carboxy, alkyloxycarbonyl, halo, ary], haloaryl or aryloxycarbonyl group; or wherein R 2 and R' together with the carbon atoms to which they are attached form a ring system or wherein R' and R 4 together andlor R 3 and X together form one or more than one ring systems.

In the compounds of the invention it is preferred that X represents a C3 chain as the indications are that 2 5 such compounds give rise to the more active compounds. However, compounds of interest can also be secured where X is a Cl, C2 C4, C5 or C6 straight chain of carbon atoms.

Other compounds of interest are those where X is an unsaturated residue and interest here centres particularly upon those compounds containing a chain of three carbon atoms with one site of carbon-to-carbon unsaturation. The synthetic methods thatwe adopt lend themselves most readily to the production of compounds containing one olefinic double bond and this may be located between the two carbon atoms nearest to the piperazine ring or between the two carbon atoms furthest from the piperazine ring.

Compounds in which at least one of the hydrogen atoms in the X residue represents a heavy isotope of hydrogen are of particular interest in tracer experiments. Such radio- active compounds will normally contain two heavy hydrogen atoms since such compounds are most easily prepared by hydrogenation of a compound of the invention containing an olefinic double bond in the group X using tritium.

Our previous investigations with acyclic amino acids have shown that the acidic group represented by the group Y is preferably a phosphonic acid or esterthereof and the same preference exists in the piperazine carboxylic acids of the present invention. Whether the phosphonic acid is present in the mono- or di-ester form or in the free acid form will be governed partly by the manner in which it is desired to use the compound since, while the indications are that it is the free acid form of the compound that exhibits the best activity, certain iipophilic residues are advantageous in the compound to secure passage of the compound through the blood brain barrier to direct the compound to its ultimate side of activity. The present indications therefore are that while in vitro activity is best demonstrated by compounds in which R' and R' are both hydrogen, for certain clinical uses it is preferrred that one or both of R' and R' represent an organic residue 45 of the type defined above. When R6 and/or R 7 represents an alkyl group, it is preferred that this contains 1 to 6 and particularly 1 to 4 carbon atoms and methyl, ethyl, n-propyl and n- butyl esters are of interest. When R 6 and/or R 7 is an aryl group, it is preferred that this is a phenyl group although, in certain circumstances, polynuclear aryl residues such as naphthyl residues are of interest because of their effect on the hydrophilic/lipophilic balance of the compound. The hydrophilic/lipophilic balance of the compound can also 50 be influenced by the presence or absence of any halogeno substituents present and here, mention may be made of fluoro, chloro or bromo substitution.

As an alternative to a phosphonic acid residue as the group Y, compounds of the present invention can contain a sulphonic, sulphinic, carboxylic or boronic acid residue and, as mentioned above, these acid residues can be present in free acid form or in an ester form, similar considerations applying to the presentation of the compound in free acid or ester form and, in the latter case, to the selection of the esterifying residue.

Further alternative groups for Y may include phenol or uracil, or hydantoin, or barbituric acid or isoxazole, or oxadiazolidindione residues, or other groups providing similar electronegative sites.

The residue R' in the compounds of the invention is also introduced to influence the hydrophilic/lipophilic 60 balance of the compound. In the simplest compounds of the present invention, R 4 will be hydrogen but alternative structures include compounds where R 4 represents an alkyl or alkoxy group normally containing up to 6 carbon atoms and preferably containing 1 to 4 carbon atoms such as a methyl, ethyl, n-propyl or n-butyl group. When R 4 represents an alkoxy group, the alkoxy group may contain 1 to 6 and preferably 1 to 4 carbon atoms such as methoxy, ethoxy, n-propoxy or n-butoxy. R 4 may also be a hydroxy group. When R 4 65 3 GB 2 157 685 A 3 is an aryl, aryloxy, aralkyl, aralkoxy or aralkylamino group, the aryl residue is preferably a phenyl residue although the aryl residue may also be a polynuclear residue such as naphthyl. Aralkyl, aralkoxy and aralkylamino residues may be residues in which the alkyl portion contains 1 to 6 and preferably 1 to 4 carbon atoms. The alkyl or aryl residue in these compounds may be substituted by at least one halogeno group such as a fluoro, chloro or bromo group. The hydrophilic/lipophilic balance of the compounds of the invention can also be favourably influenced by the presence of a morpholino substituent as the group R 4.

R can represent hydrogen or an alkyl, haloalkyl, aryl, haloaryl, aralkyl or haloaralkyl residue. When R represents an alkyl group, it may contain 1 to 6 and preferably 1 to 4 carbon atoms and the aryl residue may be phenyl or a polynuclear residue such as naphthyl. Alkyl or aryl residues may also be substituted by one or more halogeno groups such as fluoro, chloro or bromo groups. The group R may be identical to the group R 6 10 and/or R' and the synthetic methods adopted often will most easily give compounds in which the groups R, R6 and, when present, R 7 are identical.

R' may also represent hydrogen or an alky], haloalky], aryl, haloary], aralkyl or haloaralkyl group and, as for the group R, the alkyl groups may contain 1 to 6, preferably 1 to 4 carbon atoms and the aryl groups may be phenyl or polynuclear residues such as naphthyl. When halogeno substituents are present, they may be 15 one or more fluoro, chloro or bromo substituents.

The groups R', R 3 and R5 which may be the same or different, may each be hydrogen or an alkyl, hydroxy, alkoxy, carboxy, alkyloxycarbonVI, halo, aryl, haloaryl or aryloxycarbonyl group and once again, alkyl groups may contain 1 to 6 and preferably 1 to 4 carbon atoms and aryl groups may be phenyl or polynuclear residues such as naphthyl. When substituents are present, these may be one or more fluoro, chloro or bromo groups. Alternatively, R 2 and R' may, together with the carbon atoms to which they are attached on the piperazine ring, form a ring system which may be of aromatic character such as a benzene ring so that the whole ring system is a 1,2,3,4- tetrahydro-quinoxaline which may be substituted.

When the groups R, R', R 2 and R 3 represent alkyl or substituted alkyl groups, it is preferred that the alkyl groups be methyl, ethyl, n-propyl or n-butyl.

When the group 2 5 1 R4Xy 30 is a carboxylic acyl group, it may be derived from a carboxylic acid RICOOH where R' is a saturated or unsaturated aliphatic hydrocarbon residue containing up to 6 and preferably up to 4 carbon atoms or an aromatic ring, e.g. phenyl or naphthy], where the aliphatic residue or aromatic ring can be unsubstituted or 35 substituted by one or more halogeno, carboxy, hydroxy or Cl-C6 alkoxy groups. Preferably, the carboxylic acyi group is derived from benzoic acid or a benzoic acid substituted in the ring by one or more F, Cl or Br groups.

When the compounds of the invention contain both basic and acidic functions either or both of the basic and acidic functions can be prepared in the compounds of the invention in salt form. Thus, for formulation 40 reasons, it is often desirable to prepare the 2-carboxylic acid residue and/or the acid residue Y in the form of a physiologically acceptable water-soluble salt such as the sodium salt. Compounds of the invention in which the groups COOR and Y are in the form of the free acid or an ester thereof or a salt thereof can be prepared in the form of salts of the basic amino groups and here, salts of interest are physiologically acceptable acid addition salts, such as salts with hydrochloric acid, acetid acid, succinic acid, tartaric acid, or 45 citric acid.

The compounds of the invention will always contain a centre of asymmetry at C2 and possibly elsewhere.

The compounds of the present invention include both racemic mixtures and compounds in which C2 is substantially completely in the R or substantially completely in the S configuration.

The compounds of the invention can be prepared by reacting a piperazine-2carboxylic acid or ester of the 50 formula Ill:

with a compound of formula R R 3 F 5 R 2),: 11 R R4 1 Z-X-Y 1 i '_7 c 0 C) R 4 GB 2 157 685 A 4 in which formulae R, R', R 2, R 3, R 4, R 5, X and Y are as defined above and Z represents a reactive group such as a halogeno group or p-tosyl group. This condensation reaction will normally be carried out under basic conditions. Where R4-X-y together represents or contains an acyl group, the compounds can be prepared by reaction of the piperazine with the corresponding acyl halide or other activated acyi precursor, again under basic conditions.

More specifically, compounds of the formula IV that may be used include compounds in which the acidic residues in the group Y are in the form of an ester. For example, in the preferred compounds of the invention in which Y represents a phosphoric acid residue, Y in the compound [V can be a phosphonic acid dialkyl ester. Following the condensation reaction, one or both of the ester groupings can be hydrolysed under acidic conditions if desired to give a corresponding invention compound in the form of the free phosphonic 10 acid. When it is desired to prepare compounds in which the acidic residue Y is a sulphonic or sulphinic or carboxylic or boronic acid residue, the experimental methods we have adopted indicate the use of intermediates [V in which the group Y is in the free acid form. If the synthetic methods adopted result in the production of invention compounds in which the group Y is in free acid form, then these acidic groups can be subsequently esterified or converted into salts as desired. Alternatively, where phosphonic acid compounds 15 are to be prepared, these will normally be prepared in the ester form, as indicated above, and if desired, the esters can be subsequently converted into free acid or salts and reconverted into alternative ester forms if required.

When it is desired to prepare invention compounds in which X contains carbon-to-carbon unsaturation, the intermediate IV can be one in which the group X contains corresponding carbon-to-carbon unsaturation. 20 This will give rise to an invention compound having corresponding carbon-to-carbon unsaturation although occasionally it is found that migration of the carbon-to-carbon unsaturation occurs. Invention compounds containing carbon-to-carbon unsaturation in the group X can be used as such or can be regarded as intermediates forthe production of invention compounds in which X represents a saturated group. Thus, the sites of unsaturation can be hydrogenated catalytically under conventional conditions either using hydrogen 25 or using tritium to introduce sites in the molecule for tracer work.

It is usually convenient to use intermediates [V in which Z represents a reactive halogeno group, preferably chlorine or bromine but, as indicated above, other synthetic methods can be adopted for reaction at a basic nitrogen atom to introduce the group WY onto the piperazine ring.

Intermediates Ill can be obtained by hydrogenation of the corresponding pyrazine carboxylic acids. This 30 reduction will normally give rise to a compound that is racemic at C2 but where individual isomers are required, resolution of hydrogenation products will be carried out prior to reaction with intermediate IV, or the final condensation products will be resolved.

When it is desired to produce the invention compounds in the form of salts, salt formation will normally be effected subsequent to reaction of Ill with]V, but some condensation reactions may give rise to salt products 35 directly.

In accordance with a further feature of the invention, we provide a pharmaceutical composition comprising a compound of formula 1 in association with a pharmaceutically acceptable diluent or carrier. The compounds of the invention act on the central nervous system and may be administered parenterally or orally, e.g. intravenously for acute treatment, or subcutaneously or orally for chronic treatment. Compounds 40 of the invention will be formulated for clinical use in suitable vehicles, normally as a preparation of a water-soluble salt, though preparations of low water solubility, possibly in association with physiologically tolerable emulsifying agents, may be used for depot administration.

Since it is believed to be necessary for compounds of the invention to penetrate the blood brain barrier, it is frequently necessary to administer the compounds of the present invention in amounts significantly in excess of the amounts necessary to be achieved within the brain for the therapeutic effect desired and this will influence the concentration of the active compounds in the compositions of the present invention.

Considerations of this type suggest that compositions of the invention might contain the active compound in a concentration such that a conventional dosage volume would provide the subject with up to about 200 mg/kg body weight although, when the compounds are to be administered by the intravenous or subcutaneous route, dosages in the region of about 1-20 mg/kg body weight are to be expected for the more active compounds andlorfor those substances with a high lipophilicto hydrophilic balance.

In accordance with a furtherfeature of the invention, we provide compounds of formula 1 for use in a method of therapy practised on the human or animal body. More specifically, the compounds of the invention have been found to antagonise responses of mammalian central neurones to excitatory amino acids and also to depress spontaneous and evoked synaptic activity in the central nervous system. Amino acid receptors mediate or modulate synaptic excitation of many excitatory synapses in the brain. The compounds of the present invention can modify abnormal central nervous system activity involving amino acid receptors and consequently are of interest in providing beneficial intervention in cases where such abnormalities arise.

10 The following Examples are given to illustrate the invention. Temperatures are in 'C.

Example 1

Synthesis of 3- (-)-2-carboxypiperazin-4-yl)propyi-1 -phosphonic acid (CPP).

Br-CH=CH-CH 2_ PO(OC 2 H 5)2 + H 'I C1,z - COOH H (b) H 2 _ (c) H+ (a) OH / CH=CH-CH2-PO(OW0C 2H5 1 CI)""OOH H CH 2-CH2-CH 2-PO(OH) 2 COOH H GB 2 157 685 A 5 (a) Ethyl 3-((:i-)-2carboxypiperazin-4-yl)-prop-2-enyl1-phosphonate To a solution of piperazine-2-carboxylic acid (8g, 0.06 mole) in water (50 mi) containing sodium hydroxide 25 (7.2 g, 0.18 mole) was added diethyl 3-bromo-prop-2-enyi-l-phosphonate (15.75 g, 0.06 mole). The resulting solution was stirred and maintained at 65-700 for 12 h. The solution was allowed to cool, neutralized with dilute hydrochloric acid to pH 7, and applied to Dowex (R.T.M.) AG-50 H' resin. The ninhydrin-positive aqueous eluates were combined and evaporated under reduced pressure to yield 9 g ethyl 3-((i:)-2 carboxypiperazin-4-yl)-prop-2-enyl-1 -phosphonate as a white solid which was used in the next step without 30 further purification.

(b) Ethyl 3-(( )-2carboxypiperazin-4-yl)-propyl 1-phosphonate A solution of ethyl 3((+)-2-ca rboxyp i perazi n-4-yO pro p-2-enyM -p hosph o nate (5.0 g) in 7 M aqueous ammonia solution (50 mi) was hydrogenated over 5% palladium on charcoal (1 g) at room temperature and 35 atmospheric pressure until no more hydrogen was taken up. The resulting solution was evaporated under reduced pressure to yield ethyl 3((:-)-2-carboxypiperazin-4-yl)-propyl-l- phosphonate. (4.8 g). Recrystalliza tion from ethanol gave a white solid, m.p. 140-4.

Calculated for C101-121N205P: C 42.8; H, 7.5; N, 10.0% Found: C, 42.8; H, 7.6; N, 9.8% (c) 3-((.t (-2-Carboxypiperazin-4-yl)-propyl- 1-phosphonic acid A sol ution of ethyl 3-((-t)-2-carboxypiperazin-4-yl)-propyi-1 phosphonate (4.7 g) was taken up i nto 6 M hydrochloric acid (100 m 1) and the resu lting solution was boiled u nder reflux for 2 h. The solution was evaporated to dryness and the residue was taken up into minimum volume of water for application to a Dowex AG-1 -acetate resi n col umn. The product, 3-((.-t)-2- carboxypiperazin-4-yi)-propyi-1 -phosphonic acid, was eluted from the resin with 0.1 M acetic acid. Following evaporation of the eluate, the residue was recrystallized from aqueous ethanol yielding 3.9 g of a white solid, m.p. 174-5'.

Calculated for CBH17N205P. 1 H20: C, 35.5; H, 7.11; N, 10.4% Found: C, 35.9; H, 7.5; N, 10.0% Example 2

Synthesis of 3-(.t)-2-carboxypiperazine-4-yl)-propane-l-sulphonic acid. (CPS) H Br-CH 2_ CH 2-CH 2_ so 3 Na QX hane H COOH (a) OH-(b) ion exc (7H 2-CH 2 CH 2 so 3 H COOH Sodium 3-bromo-propane-1 -su 1 phonate (2.25 g, 0.01 mole) was added to a solution of piperazine-2 carboxylic acid (1.3 g, 0.01 mole) in aqueous sodium hydroxide (0.9 g NaOH130 mi H20). The resulting solution was maintained at 60-650 for 12 h. The product, 3(( )-2- carboxypiperazin-4-yi)-propane-1 -sulphonic65 6 GB 2 157 685 A 6 acid, was isolated by passage of the reaction mixture through Dowex-AG-1 acetate resin. Evaporation of the column filtrate and aqueous washings and recrystallization of the crude product from a 50% aqueous ethanol solution yielded 3-((.t)-2-carboxy-piperazin-4-yl)-propane-l-sulphonic acid (500 mg) as a white crystalline solid, m.p. 190-191% Calculated for C81-116N205S. 1 H20: C, 35.5; H, 63; N, 10.4% Found: C, 35.8; H, 6.8; N, 10.2% Example 3

Synthesis of 2-((-t)-2-carboxypiperazin-4-yi)-propionic acid.

H e:COOH H CH3 OOH H COOH CH -CH-COOH 3 1 cl OH 1,11 1 Piperazine-2-carboxylic acid (1.3 g, 0.01 mole) and 2-chloropropionic acid (1.1 g, 0.01 mole) were dissolved in aqueous sodium hydroxide solution (0.9 g NaOH120 mi H20) and the resulting solution was maintained at 20 60-65'for 12 h. The product was isolated by ion-exchange chromatography on Dowex AG-1-acetate resin with elution by 0.3 M acetic acid. Recrystallization from 50% aqueous ethanol yielded 2-((.t)-2 carboxypiperazin-4-yi)-propionic acid (520 mg) as a white solid, m.p. 1734.

Calculated for C8H14N2041/21-120: C, 45.9; H, 7.2; N, 13.3% Found: C, 45.7; H, 7.5; N, 13.6% Example 4 Synthesis of 4-(4-bromobenzoyi)-piperazine-2,3-dicarboxylic acid (BBP).

O=C--C-Br H 1 - OOH Bre- COC1 COOH C::CCOOH OH- C)COOH H H To an ice cold solution of piperazine-2,3-dicarboxylic acid (1.74 g/0.01 mole) in aqueous sodium hydroxide (1.2 g/20 mi) was added 4-bromobenzoyi chloride (2.2 g/0.01 mole) over 30 min. The resulting solution was stirred at 0'for 2 h, then allowed to warm to room temperature overnight. The solution was applied to a column of Dowex AG-1 -acetate resin and the ninhydrin positive fractions of the 3 M acetic acid eluate were combined and evaporated dryness. Recrystallization of the residue from a 50% aqueous ethanol solution 4 Table 1. Chemical shift 6 ( pm) values fo H 1 NMR spectraf Invention com ounds.

(H 2)3PO(OH)2 r N, 1 N- -COOH (Cl Hh S03T1 u)" COOH H CH3-CH-COOH IN cool 1 COoll 11 C0011 11 0 1 -nil-30-40 mg/ml D 2 0.

Spertra obtained on n Joel FX 200 R17 lnqtrurnent, qnmple concentrations in the" r 1 HN o0H COOH 1),200H Q d N ",H H 1 411 m V7-32 211 m 28-3.2 111 dd 3,14 CH 2-CH 2-C!!2-PO(ON)2 CH 2-T2-CH2- PO(Oll)2 C!!2-CH 2-CH 2-PO(ON) 2 I'S-17 m 1.74-2.0 3.2-3.6 4H m 32-36 2W m 41-4.2 1H dd 4.24 CH 2-CH 2-T2-SO311 CH 2-C92-CH2-SO3H T2- '2-CH2SOP m 2 96-3.04 m 2.16-2.32 3.13-3.9 411 m 2-6-33 2H m 308-3-28 111 dd 3.12 CH 3-CH CH 3-CII-COOH d POS m 3-96 4-CH 2-T2-M 4 Hz Ar 411 m 732-7.88 N-CH-CII-N cl s. dd 5. 10 j HH m 2.6-3.4 N-CH-CIT-N trans dd 3.92 J 13 11z -n n 0 0) (D 0 n n W z "0 ul 6p zn 11 P.

00 OR (D CL Cr 0 ::i i 0 w- (D N 0 CD Cl) N :3,p 00 C C 3 CD U) 0 N) 00 1 i i i co W 3 = CD CL 0 CL 0 0 m X CD CD 0 (n Z cr = 0 (D CD CD 1 X 0 m 0 0 0 ct 0 0:3 0 CD (D Cl 0 (h 0 CD C) = 0 < CD CD R -6 0 0:3 :3: =r < =r < Cr (D cn Cr CD (D:3 CD CD CL M (D cc r (D:3 (D R 4 1 X - y 3 1 R N R 2 'N):c0OR 1 1 R 1 1 t 1 Method as in Example No.

1 1 R, R 1 R 2, R 3 R 4 1 -X-Y Formula Calc.

N Found M.P. (c) HVE a H H H H H H H H H -(CH 2)3_ PO(OH) 2 -(CH 2)3_ PO(OH)OC 2 H 5 -(CH 2)2-PO(O1-1) 2 -(CH 2)2- PO(O1-1)0C 2 H 5 -(CH 2)2_ PO(OH) 2 -(CH 2)3-SO 3 H -(CH 2)2 so 3 H -CH 2- COOH CH CH-COOH 3-1 -(CH 2)2-COOH -(Cif 2YCOOH 0 -Cif 2 \N 11 H H H H COOH 11 H H H c 8 H 17 N 2 0 5 P.(1H 2 0) c 10 H 21 N 2 0 5 p c 7 H 15 N 2 0 5 P.(2H 2 0) c 9 H 19 N 2 0 5 P(11,1 2 0) c 8 H 15 N 2 0 7 M1H 2 0) c 8 H 16 N 2 0 5 SM 2 0) c 7 H 14 N 2 0 5 S(IH 2 0) c 7 H 12 N 2 0 4 QH 2 0) c 8 H14 N 2 0 4(P,,H20) c 8 H 14 N 2 0 4 (;,-H 20) c 9 11 16 N 2 0 4 10.4 10.0 10.2 9.9 9.3 10.4 10.9 14.2 13.3 10.1 174-5 9.8 140-4 10.1 197-8 10.0 8.7 10.2 10.9 14.0 1J.6 0.2 0.1 0.6 0.5 2.6 0.8 1b 1b 224-6 242-4 226-7 178-9 173-4 2 2 3 3 3 3 0.48 0.1 H H H H 13.3 13.0 13.3 172-3 13.1 0.1 0.37 3 H H C10H 14N4 0 4 22.0 21.9 285-7 0 3 11 -rll)- (70011 cool 1 C8111 2N2 0 6 12.0 11.7 260-1 2.1 i 0 -r- -rl W W N rli -1 1 C C) Cn a Method R, R R 4 R 5 Formula N In.p. HVE as in 2 3 Calc. Founj (c) Example No. R R -X-Y 3 H - (CH2) 3 COOH COOH c 10 H 16 N 2 0 6 10.8 11.3 1 1 97-9 2.0 3 H -CH 2 COOH c 11 H 14 N 4 0 6 18.8 18.4 91-3 1.7 H 4d H -CO-(CH 2)2-COOH H c 9 H 14 N 2 0 5 12.2 11.8 217-8 0.35 4 H COOH C 13 H 14 N 2 0 5 10.1 10.1. 185-6 1.9 4 H -CO-C- cl COOH C13 H 13 N 2 0 5 cl(SH 2 0) 8.7 8.6 216-7 1.6 4 H -CO-W- Br COOH C13 H 13 N 2 0 5 Br 7.8 7.8 218-220 1.9 HOOC 4 e H -CO COOH C14H14N 2 0 7 (1H 2 0) 8.2 8.1 227-9 2.5 4 H -CO COOH C13 H 13 N 2 0 5 cl cl 4 H -c COOH C13 H 13 N 2 05C1 4 H -CO-1 cl COOH C13 H 12 N 2 05C1 2 (a) Anionic mobility in high voltage paper electrophoresis (4000 V, 72V/cm, 0.2M NaOAc buffer, pH 4-0, 20 min.) relative to L-glutamate = 1.0 (b) Halogeno reactant IV saturaed: no hydrogenation step. (c) Reactants heated at reflux temperature for 2 hours instead of at 60-65 for 12 hours. (d) (e) Succinic anhydride used as reactant IV Phthalic anhydride used as reactant IV M W W D. P.

0 tn 0 m 0 W W K) fli tn 0 W 0 G; 2; (n i i 1 W 1 m GB 2 157 685 A The compounds of the invention have antagonist action at excitatory amino acid receptors in the central nervous system. There are several different types of these receptors, some or all of which are intimately involved in central nervous function. Three types of receptors that have been described in the neuroscientific literature are known as N-methy]-Daspartate (NIVIDA), kainate (K) and quisqualate (G) receptors. The compounds of the invention have differential actions at these receptors, some being more effective at NIVIDA receptors and others at K or Q receptors. Compounds which act at excitatory amino acid receptors can affect the action of natural amino acid transmitter substances and thereby influence the electrical activity of the central nervous system.

To evaluate actions of substances at amino acid receptors on nerve cells (neurones), the substances may jo be tested on spinal cord neurones, which have similar characteristics to nerve cells in the brain. Typically, the 10 isolated spinal cord of the frog or 4-8 day old rat is used, and compounds are tested for their ability to affect the activity of spinal neurones induced by excitatory amino acids or by electrical stimulation of afferent fibres, Table 2 shows the relative potencies of some invention compounds relevant to previously known excitatory amino acid antagonists.

The most potent NMIDA antagonists previously known were 2-amino-5phosphonopentanoic acid (AP5) and 2-amino-7-phosphonoheptanoic acid (AP7), and y-D-glutamyigiycine (yIDGG) was one of the most potent previously known antagonists of kainate and quisqualate. From Table 2 it can be seen that the invention compound 3-((-t)-2-carboxypiperazin-4-yi)-propy]-1-phosphonic acid (CPP) is more potent as an antagonist of NIVIDA and of polysynaptic spinal excitation than is either AP5 or AP7. The invention compound 4-(4-bromobenzoyi)-piperazine-2,3-dicarboxylic acid (BBP) is a more potent antagonist of kainate 20 and quisqualate-induced depolarizations than is yDGG, and is also more potent as a depressant of monosynaptic excitation.

NIVIDA receptor antagonists have been shown to have anticonvulsant activity. Amongst known excitatory amino acid antagonists, AP7 was previously the most potent anticonvulsant. Table 3 shows that CPP has significantly higher anticonvulsant activity than AP7 when tested against 3-mercaptopropionate-induced 25 convulsions in mice.

0) m -p c- u) r,,) o -n C) (D r CL 0 C =3 - r_ U) U) 0 - 3 C0 c) " CD Cn (D 2) 0 (D (D pr S - 2. c =r = 1 Cr 0_ CD (D 0 0 ID;W CD < 0 a -- -0 :3 (D CDCr 3 rj) C) 0 U) =r < (D (D 0 - CD (D (D 0 6) > 0 D- Cn:3 (D CD 0_ CD CD) U) (D 3 C, 0 CL - 0 (D, =r (D CD (D N) 0,2) W 0 0 m Z LO CD CD, 7;7, r 0 U) C"o=-OM CD:3Ct D. =r - - - 0 < 0 M 0 0 0 3 r CD U2 cl) < 2) U) (D CD CD - (D =F W D- c- (D 1 (D C) r C,) C7 -C - CJ:3 C7 0 01 to 0 CD U) a) (D:3 (D U);;:

(D = =r U) R' '= C) (D 0 0 m 0 D- CD CD = -' " = CD 0 CD < 0 CD = 0 0 = 0 -1 c- = r --h CD U) 0 0 m 0 0 Cc (D (D CD CD C) j 0 (D 0 10 = D- 110 D-:' = Cl) 0. (D 0 CD W c) C) 0 0 Cn XROMOM0 r W < CD (D C) D- M 0 (D :3 = m 0 U) c:

0 k :3 - C) (n ún - "c CD CD:3 O - CL.

:3 0 CD:3 0 - 0 0 -m (D Cl) - :3 < 0 (n 0 CD C) v 0 CD ", CD :3 U):3 U) C0(D : Z C) U) (D c) (D (D fj) 0 0 CL a) 0 0 0 1 0 0 Q- (D C) CD 0 ( =r (D D C0 0-0 0 (D 0 < CD 00 0 0 0 0) a) m al CD M C.n 0 Cf) Test Compound 0 W =3 M Cf) (D X 0 h 0:3 CD r 0:3 (D U) Synaptic Excitationi Conc.

(pm) MS yDGG 700 24 APS 2 AP7 3 CPP 015 CPS 500 6 BBP 100 24 Per cent depression PS 27 28 28 32 8 Amino Acid-Induced Depolarization 2 MA 1-0 a ' b 0-18 a 017 b 0.2 a 0.25 b 0.03 b K Q 1.0 alb. 1.0 a 1 b.

19. 5a 6.5a 19. a 7. a 4.7 b 5,1 b 4.3 b 0.62 b 0,47 b =r -1 (D a) 3 2:

(D (D CD 0- m CD 0 0 0 CL U) CD W m C) CD X 0 (D D- 3 0 CD c: 0 CL CD,0 0 N 0 CD CL 00 Cn 1 12 GB 2 157 685 A Abbreviations: -yDGG, y-D-glutamyiglycine; AP5 (t)-2-amino-5- phosphonopentanoic acid; AP7,(-)-2-amino-7phosphonoheptanoic acid; CPP, 3(( )-2-carboxypiperazin-4-yi)-propyi-l-phosphonic acid; CPS, 3-(( )2carboxypi perazi n-4-yl)-pro pan e-1 -su 1 p ho nic acid; B13P, 4-(4bromobenzoyi)-piperazine-2,3-dicarboxylic acid.

Table 3. Relative potencies of phosphono compounds as antagonists at neuronal NIVIDA receptors and as anticonvulsants.

12 Depression of NMDA-induced and Anti-convulsant Compound synaptic exTitation in rat Activity (miceP 10 spinal cord NMDA Synaptic AP5 1.0 1.0 0.1 15 AP7 0.75 0.75 1.0 CPP 6 4 2.5-5.0 1 Relative potencies of substances as antagonists of NIVIDA-induced motoneuronal depolarization and as depressants of spontaneous and dorsal root-evoked ventral root synaptic potentials in spinal cord of 4-day-old rat; bath administration of drugs.

2 Relative anticonvulsant potencies of substances in mice injected with 3mercaptopropionic acid (3-MP), 100 mglkg; 3-MP and the phosphones injected subcutaneously. Abbreviations: NIVIDA = N-methyl-D-aspartic acid AP5 = DL-2-amino-5-phosphonopentanoic acid AP7 = DL-2-amino-7-phosphonoheptanoic acid CPP = 3-((.t)-2- carboxypiperazin-4-yl)-propy]-1-phosphonic acid (general formula 1, R=W=R 2 =R 3 =R 4 =R 5 =R 6 =R 7 =H; X=-CH2-CH2-CH7, Y=P031-12)

Claims (15)

1. A compound of the general formula 4 40. 1 40 X - Y R3 1 5 2 en R 11 C" 1 wherein X is a C,-Ce, straight chain saturated or unsaturated hydrocarbyl group, the group R 4 and the group Y are situated in any position in this chain and wherein one or more of the hydrogen atoms in X can be a 50 heavy isotope of hydrogen; R 4 is hydrogen or an alkyl, alkoxy, hydroxy, aryl, aryloxy, aralky], aralkoxy, aralkylamino, or morpholino group wherein the alkyl or aryl part of any one of said groups may be substituted by one or more halogeno groups; or R 4, together with at least one carbon atom of the group X, forms a carbocyclic or heterocyclic ring of 5 to 6 ring atoms; Y is an acidic or related group giving rise to one or more electronegative sites in the group; or R4-X-y represents a carboxylic acyl group; R is hydrogen oran alky], haloalkyl,a 1,haloaryl,aralkyl orhaioaralkyl group; R' is hydrogen or an alkyl, haloalkyl, ary], haloary], aralkyi or haloaralkyl group; R', R' and R5 which may be the same or different is each hydrogen or an alky], hydroxy, alkoxy, carboxy, 60 alkyloxycarbonVI, halo, ary], haloaryl or aryloxycarbonyl group; or R 2 and R 3 togetherwith the carbon atoms to which they are attached form a ring system or R' and R'together andlor R 3 and X together form one or more than one ring system; or a physiologically acceptable salt thereof.

2. A compound as claimed in claim 1 wherein Xis Cl-C4 hydrocarbyl group.

13 GB 2 157 685 A A compound as claimed in claim 2 wherein Xis a C3 straight chain saturated or unsaturated hydrocarbyl group.

4. A compound as claimed in claim 3 wherein Xis mono-unsaturated.

5. A compound as claimed in anyone of claims 1 to 4 wherein Y is selected from:

0 11 -P -OR

6 lia 1 OR 7 or 13 0 - S - OR 6 lib 15 11 U or 0 il -S OR 6 lic or 25 0 OR 6 lid 30 or 0 11 - B - OR 6 11 U lie where R'and R 7, which may be the same or different, each is hydrogen or an alkyl, haloalkyl, aryi, haloaryl, 40 aralkyl or haloaralkyl group; 6. A compound as claimed in claim 5 wherein Y is a phosphonic acid or ester thereof.

7. 3-((-)-2-carboxypiperazin-4-yi)propyi-l-phosphonic acid.

8. A process for producing a compound according to anyone of claims 1 to 7 comprising reacting a piperazine-2-carboxylic acid or ester of the formula Ill:

R 3 50 C 0 CD.R with a compound of formula W 55 R 4 1 Z-X-Y IV 60 in which formulae R, R', R 2, R 3, R 4, R', and Y are as defined in claim 1 and Z represents a reactive group.

9. A process for producing a compound according to claim 1 wherein Xis a saturated hydrocarbyl group comprising (a) reacting a piperazine-2carboxylic acid or ester of the formula Ill:

14 GB 2 157 685 A with a compound of formula IV R 4 1 Z-X-Y 11 COOR R 11 14 in which formulae R, R', R 2, R 3, R 4, R 5, and Y are as defined above and wherein X is an unsaturated hydrocarbyl group and Z represents a reactive group and (b) subsequently catalytically hydrogenating the product of step (a).

10. A process according to claim 8 or claim 9 wherein Z is a reactive halogeno or p-tosyl group.

11. A pharmaceutical composition comprising a compound according to anyone of claims 1 to 7 and a 20 pharmaceutically acceptable diluent or carrier therefor.

12. A compound according to anyone of claims 1 to 7 for use in a method of therapy practised on the human or animal body.

13. A compound according to claim land specifically named herein.

14. A compound according to claim land substantially as herein described with reference to anyone of 25 the Examples.

15. A process according to claim 8 and substantially as herein described with reference to anyone of the Examples.

Printed in the UK for HMSO, D8818935, 9185, 7102.

Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.