KYNURENIC ACID DERIVATIVES, THEIR PREPARATION AND PHARMACEUTICAL COMPOSITIONS CONTAINING THEM

Abstract: The compounds of formula (I) (R, R1, R2, R3 and R4 as defined in the specification) are useful as therapeutic agents for the treatment of pathologies of the Central Nervous System.

Description: KYNURENIC ACID DERIVATIVES, THEIR PREPARATION AND PHAR¬ MACEUTICAL COMPOSITIONS CONTAINING THEM The present invention refers to kynurenic acid de¬ rivatives useful as therapeutic agents, to a process and intermediates for their preparation and to pharma¬ ceutical compositions containing them. The compounds of the invention have the following general formula I wherein: R is hydroxy or a physiologically acceptable group which may be converted jLri vivo to OH group; R.. is hydrogen or a physiologically acceptable group which may be hydrolized _in vivo to give the free thio group; R_ , R 3 or R. , which are the same or different, are hy¬ drogen, halogen (chlorine, bromine, iodine or fluo- rine), C,-C 8 alkyl, C,-C 8 alkoxy, C,-C 8 alkylthio, ' tri- fluoromethyl, nitro, cyano, c - ι ~ c - haloalkoxy, C-,-C fi alkoxycarbonyl, C χ- 8 acyl, hydroxy, c ~ c - acyloxy groups. Physiologically acceptable groups for R and R, are widely known and used in medicinal chemistry: typical examples of R groups include ester groups such as methyl, ethyl, t-butyl, pivaloyloxymethyl, t-butoxy- methyl and the like and amides. Examples for R. groups include alkyl groups such as methyl or ethyl groups, benzyl groups, acyl groups such as acetyl, benzoyl, 2- or 2-tenoyl groups, or even disulfides obtained by oxydation of compounds I them¬ selves, in which case the R, group has the following formula: In the compounds of formula I, C. -C^. alkyl prefe- rably means methyl or ethyl; C--C-. alkoxy is preferably methoxy; C,-C β acyl is preferably acetyl; C--C 8 alkyl¬ thio is preferably methylthio; C.-C, alkoxycarbonyl is preferably methoxy or ethoxycarbonyl. Preferred meanings for R_ , R_ , R. are hydrogen, chlorine (chlorine, bromine, fluorine or iodine), C.-C,- alkoxy, trifluoromethyl. Preferred compounds of formula I are those wherein R and R. are hydrogen, at least one of R„ , R_, and R. is hydrogen and the other two have the above defined mea- nings; more preferably one of R_ , R, , R. is hydrogen and the other two are independently hydrogen, chlorine, trifluoromethyl or methoxy. When one or more R_ , R, or R. group are halogen, they are preferably chlorine in the position 5 and/or 6 and/or 7. The invention concerns also the pharmaceutically acceptable salts of compounds of formula I with non- toxic acids or bases. Typical compounds of the invention are: 4-thio-guinoline-2-carboxylic (thiokynurenic) acid 7-chloro-4-thio-guinoline-2-carboxylic acid 7-bromo-4-thio-quinoline-2-carboxylic acid 7-fluoro-4-thio-quinoline-2-carboxylic acid 6-chloro-4-thio-quinoline-2-carboxylic acid 6-bromo-4-thio-quinoline-2-carboxylic acid 6-fluoro-4-thio-quinoline-2-carboxylic acid 5-chloro-4-thio-quinoline-2-carboxylic acid 5,7-dichloro-4-thio-quinoline-2-carboxylic acid 5-chloro-4-thio-quinoline-2-carboxylic acid 7-trifluoromethyl-4-thio-quinoline-2-carboxylic acid 5-chloro-7-trifluoromethy1-4-thio-quinoline-2-carboxy- lie acid 7-methoxy-5-methyl-4-thio-quinoline-2-carboxylic acid 7-thiomethyl-4-thio-quinoline-2-carboxylic acid 6-chloro-7-thiomethy1-4-thio-quinoline-2-carboxylie acid 5-fluoro-6-chloro-4-thio-quinoline-2-carboxylic acid. The. compounds of the invention are able to counte¬ ract some of the effects of glutamate by interacting with the glycine recognition site present in the supra- molecular complex known as "NMDA receptor-ion channel complex" . The compounds I may be therefore used in human therapy for the treatment of many neurological disor¬ ders due to impaired excitatory glutamatergic tran¬ smission. In fact, an excessive presence of glutamate at the synaptic level may cause an abnormal stimulation and finally neuronal death. This death has been defined of excito-toxic type (Olney J. W. , Advances in βioche- mical Psyghopharmac. 27; 375-381; 1981). The pathology wherein an abnormal functioning of glutamatergic transmission is thought to play an important role is rather wide and it includes extremely different clinical conditions such as Chinese restaurant syndrome, some memory or learning impairments, hepatic coma, some degenerative diseases of CNS such as Huntington's chorea, olivoponto- cerebellar degeneration, lateral amyotrophic sclerosis, some retinal degenerative conditions and the like. An abnormal stimulation of the glutamate receptors causes also convulsion and is involved in hypoglycemic neuronal damage, lathyriεm and neurological disorders connected thereto (amyotrophic lateral sclerosis, Parkinson, dementia) affecting some oceanic populations eating food containing high amounts of aminoacids similar to glycine and glutamate (Science 237; 517-522; 1987) . Another field of the neurological pathology whe- rein glutamate is almost certainly involved is that of cerebral damages induced by hypoxia or ischemia. The compounds fo the invention, which may be used in the above enormous field of pathology, may be consi¬ dered derivatives of kynurenic acid, whose presence in low concentration in the brain of different animal spe¬ cies has been recognized as well as its antagonistic activity - of the glutamate effect in some classical pharmacological tests such as guinea-pig myenteric plexus (Moroni F. et al, Neuroscience Letters 68, 57- 63; 1986; Moroni F . et al, European J. Pharmacol. 163, 123-126;- JL989). It has been shown that the action of kynurenate is mainly due to its interaction with glycine: relatively low concentrations of glycine may in fact antagonise the inhibitory effect of kynurenate. Glycine should be therefore an agonist of a receptor modulating the glutamate activity, whereas kynurenate should be an an¬ tagonist of this receptor. Kynurenic acid derivatives are disclosed in EP-A-0303387 whereas the 2-chloro kynurenic acid has been already studied (Kemp J.A et al. Proc. Natl Acad. Sci Vol. 85 (17), 6547-50, 1988). The compounds of the invention proved to be en¬ dowed with more favourable pharmacological activities then the parent compound. In particular, the compounds I and thiokynurenic acid (R = OH, R_ , R_ and R. = H, R, = H) are competitive antagonists of the glycine recep¬ tors as shown by the following results: 1) they displace labelled glycine from cortical membranes with an ECou rι value 5-10 times lower than that of kynurenate; 2) they antagonise in non-competitive way the glu¬ tamate effect on NMDA receptors present on guinea-pig ileum: on this test their effect is competitively -anta¬ gonised by glycine. The introduction of an halogen atom on the benzene ring of thiokynurenate has enhanced its affinity for the glycine receptors. The compounds I were also active in mouse cerebral cortex slices according to Proc. Natl. Acad. Sci. " USA 85; 6547-6550 - 1988, in the prevention of glutamate toxicity in cultured cells and in the prevention of NMDA induced convulsions in mice. In this test the compounds I were from 3 to 50 ti¬ mes more active than the corresponding kynurenic acid derivatives. In particular 7-chloro-4-thiokynurenic acid at a concentration of 0.08 μM antagonises the glu¬ tamate neurotoxic-ity in cultured cells; at the concen¬ tration of 1 μM it displaces 50% of labelled glycine from its binding sites in cortical membranes and at a concentration of 5 μM it antagonises 50% of glutamate or NMDA actions on guinea-pig terminal ileum or on brain slices whereas 5,7-dichlorothiokynurenic acid an¬ tagonises NMDA induced convulsions in mice at doses of 5-20 mg/kg. From the above results, it is evident that 4- thiokynurenic acid and the derivatives I are competi¬ tive antagonists of a particular kind of glycine recep¬ tors. They are therefore useful for modulating the ami- noacidergic excitatory neuro-transmission, particularly for the treatment of pathological conditions cha- racterized by abnormal stimulation of NMDA receptors, such as: 1) cerebral hypoxic or ischemic syndromes where thiokynurenate could also act as radical scavenger. 2) Convulsions. 3) Hypoglycemia. 4) Cerebral and spinal thrauma. 5) Muscular spasms of central origin. 6) Neurodegenerative diseases (lateral amyotrophic sclerosis, olivopontocerebellar atrophy, ataxis etc. ) . 7) Cephalgias of different origin (the spreading depression, combined with some forms of cephal¬ gias, is antagonised by NMDA antagonists). 8) Painful syndromes difficult to treat or to dia- gnose (trigeminus neuralgia, pains due to "ghost limb" etc). 9) Encephalopathy connected with AIDS. 10) Hepatic encephalopathy. 11) Hydrocephalus. 12) Lathyrism and mussels poisoning. 13) Psycho-motor excitement. 14) Insomnia. 15) Psychiatric diseases (schizophrenia type 2; mania etc. ) For the considered therapeutic use, the compounds I will be formulated in suitable pharmaceutical compo¬ sitions using conventional excipients and methods. The compounds may be administerd orally or paren- terally at doses ranging from 0.1 to about 10 g/day. The compounds of the invention are prepared by a process comprising the reaction of compounds of formula II wherein R 2 , R 3 and , are as defined above and R' is OH or a group which may be converted in hydroxy group, with N,N-dimethylthiocarbamoyl chloride. The obtained compounds of formula III wherein R 2 , R 3 R4. and R' are as above defined, are transformed into compounds IV by treatment with acids wherein R„ , R 3 , R. and R 1 are as above defined, which are transformed into compounds I by hydrolysis and cleavage of the optional protective group. The compounds I so obtained may be transformed into "pro-drugs" by known methods of alkylation or acy- latioh of thio groups and/or esterification of the car- boxy group. The mild oxidation of compounds I yields the cor- responding symmetric disulfides. The compounds III and IV are new and are included within the scope of the invention as intermediates use¬ ful for the preparation of compounds I. The compounds II are known or they may be prepared according to known methods. For instance, easily available anilines V wherein R_ , R 3 and R 4, are as above defined , ' are reac- ted with acetylene dicarboxylate dimethyl ester to give compound II wherein R ' is -OCH., . EXAMPLE 1 a) Kynurenic acid methyl ester. An ether solution of diazomethane (100 ml, 1.5 g) was dropped during 15 min. to a suspension of kynurenic acid (3.0 g, 0.016 mmole) in distilled tetrahydrofuran (200 ml) at 0 β C and under magnetic stirring. Then the- reaction mixture is left to warm to room temperature and stirring is continued until complete dissolution of the starting product. Solvent is evaporated off to ob¬ tain a crude product which is subjected to flash chro- matography on SiO„ (d. 4 cm; h 16 cm) eluting with chloroform (800 ml) and 95:5 chloroform-methanol (800 ml). 2.2 g of the title compound are obtained (73% yield), m.p. 224-226°C. 1 H-NMR (CDC1 3 + CD 3 ) £ : 3.95 (s, 3H) ; 7.45 (m, 4H) ; 8.15 (d, 1H) ppm. b) N,N-dimethyl-thiocarbamoyl-kynurenic acid methyl ester (III). A solution of the product from step a) (700 mg, 13.4 mmoles) in distilled dimethylformamide (5 ml), -at 25°C and under magnetic stirring, is added with 1,4- diazabicyclooctane (1.35 g, 12.04 mmoles) and N,N'-di- methyl-thiocarbamoyl chloride (425 mg, 13.4 mmoles). The reaction mixture is stirred until complete disappe- aring of the starting compound, then it is diluted with water (20 ml) and cooled to =-5°C. The precipitated so¬ lid is filtered and dried under vacuum. 900 mg of (Illb) are obtained (92% yield), m.p. 131.134°C. 1 H-NMR (CDC1 3 ) rj : 3.5 (d, 6H) ; 4.05 (s, 3H) ; 7.8 (m, 4H) ; 8.4 (d,lH) ppm. IR (CDClg) : 1720, 1530 cm -1 . c) N,N-dimethyl-thiolcarbamoyl-kynurenic acid methyl ester (IV). A solution of (Illb) (200 mg, 0.70 mmole) in methanol (20 ml), under magnetic stirring, is added with 37% HCl (0.5 ml). The reaction mixture is stirred for 10 in. , the solvent is evaporated off under redu¬ ced pressure, heating to 40 C C. 200 mg of (IVc) are ob- tained, m.p. 121-124°C. 1 H-NMR (CDC1 3 ) ' 3 -l ( ε broad, 6H) ; 4.05 (s, 3H) ; 7.8 (m,2H); 8.2 (m, 1H) ; 8.6 (s, 1H) ; 9.1 (d, 1H) ppm. IR (CDC1 3 ) : 1720, 1680, 1625 cm -1 . d) thiokynurenic acid (Id). (IVc) (2.8 g, 9.0 mmoles) is suspended in 10% NaOH (30 ml) and magnetically stirred for 15 hours at room temperature. The reaction mixture is acidified with 10% HCl to pH = 4, then the precipitated solid is filtered and dried under vacuum. 2.1 g of (Id) (100% yield) are obtained, m.p. 230-233°C (dec). 1 H-NMR (CD 3 OD) δ : 7.5 (m, 1H) ; 7.75 (m, 1H) ; 7.90 (d, 1H); 8.05 (s, 1H) ; 8.75 (d, 1H) ppm. 13 C-NMR (CD 3 0D ) c5 : 121.09 , 125. 96 , 127 .16 , 129 .81 , 134 .23 , 165 , 51 ppm. MASS (m/ z ) : 205 . 6 (M + ) . EXAMPLE 2 a) 7-chloro-kynurenic acid methyl ester. A solution of 3-chloroaniline (16.6 ml, 0.15 mole) in methanol (156 ml), under magnetic stirring, is added with a solution of acetylene-dicarboxylate dimethyl ester (19.2 ml, 0.15 mole) in methanol (156 ml). The resulting solution is refluxed for 30 min. Solvent is evaporated off and the residue is taken up into 200 g of diphenyl ether. The solution is refluxed for 15 min. , then cooled and diluted with petroleum ether (400 ml). The formed precipitate is filtered, to obtain 37 g of a mixture of 5-chloro- and 7-chloro- kynurenate. This precipitate is heated to 70°C in 160 g of glacial acetic acid, then, after cooling, the insoluble 7- chloro-kynurenic acid methyl ester is filtered. 26.5 g of the product (72% yield) are obtained upon cooling; m.p. 291-292°C. b) 7-chloro-kynurenic acid. The methyl ester from step a) is added to a 10% sodium hydroxide solution (5 ml). The resulting suspension is magnetically stirred at room temperature for 30 min. , then washed with ethyl ether (2 x 3 ml) . The aqueous phases are acidified with 10% hydrochloric acid to ob¬ tain a precipitate which is filtered and dried, to ob- tain 0.170 g of the title product (76% yield); m.p. 285-287°C. " l-NMR (NaOD) 6 : 6.75 (s, 1H, H_); 6.85 (dd, 1H, J, . J o—i = 7.5 Hz; J g _ 8 = 1.5 Hz, H g ) ; 7.22 (d, 1H, Jg_ g = 1.5 Hz, H g ); 7.58 (d, 1H, J 5 _ g = 7.5 Hz, H 5 ) ppm. c) 7-chloro-kynurenic acid methyl ester N,N-di- methyl-thione-carbamate. A suspension of the ester from step a) (50 g, 0.21 mole) in anhydrous dimethylformamide is added with DABCO (82.5 g, 0.73 mole), then with N,N-dimethyl-thio- carba oyl chloride (25.9 g, 0.21 mole). The resulting suspension is magnetically stirred at room temperature for 3 hours, then it is diluted with water (800 ml) to precipitate a white solid which is filtered and dried, to obtain 65 g of the title compound (97% yield). 1 H-NMR (CDC1 3 ) & ' 3.52 (s, 6H, Me 2 ) ; 4.07 (ε, 3H, MeO) 7.5 (dd, 1H, J g _ 5 = 8.5 Hz; J g _ g = 1 Hz, H g ) ; 7.82 (d, 1H, J 5 _ g = 8.5 Hz, H 5 ); 7.97 (s, 1H, H 3 ) ; 8.27 (d, 1H, Jg_ g = 1 Hz, Hg) ppm. d) 7-chloro-kynurenic acid methyl ester N,N-di- methyl-thiol-carbamate. A suspension of the thionecarbamate (65 g, 0.2 mole) from step c) in methanol (1200 ml) is added with 16.7 ml of 37% hydrochloric acid. The suspension, the colour of which turns to yellow, is magnetically stir¬ red at room temperature for 30 minutes. Then the solid is filtered and dried, solvent is partially evaporated to obtain a second precipitation of a solid which is also filtered and dried, to obtain 64.5 g of the title compound (99% yield). 1 H-NMR (CDC1 3 ) S : 3.11 (bs, 6H, Me 2 ) ; 4.06 (s,- 3H, MeO) 7.56 (dd, 1H, J g _ 5 = 7.5 Hz; J g _ g = 1.5 Hz, H g ) ; 8.2 (d, 1H, J 5 _ g = 7.5 Hz, H 5 ) ; 8.3 (d, 1H, J g _ g = 1.5 • Hz, Hg) S.38 (d, 1H, H 3 ) ppm. e) 7-chloro-thio-kynurenic acid. Thiol-carbamate from step d) (64.5 g, 0.2 mole) is added^to a 10% sodium hydroxide solution. The resulting suspension is magnetically stirred at room temperature for 16 hours, then it is washed with ethyl ether (3 x 150 ml) . The aqueous phases are acidified with 10% hy¬ drochloric acid to precipitate a red-orange solid which is filtered and dried, to obtain 47 g of the title com¬ pound (98% yield); m.p. 200-203°C. ^-H-NMR (NaOCD) 6 : 7.03 (dd, 1H, g _ 5 = 8.5 Hz; J g _ g = 1.5 Hz, H g ); 7.43 (d, 1H, J g _ g = 1.5 Hz, H g ) 7.7 (d, 1H, H 3 ); 8.15 (d, 1H, J 5 _ g = 8.5 Hz, H 5 ) ppm. EXAMPLE 3 According to the same method of Example 2, star- ting form the suitable anilines, the following com¬ pounds were prepared: Compound m.p. 1 H-NMR (NaOD< ) 6-chloro-thiokynurenic acid 215-217 (dec) °C 7.28 (dd, IH, J 7 _g=8.5 Hz; J ? _ 5 =l Hz, H_); 7.49 (d, IH, J g _ 7 =8.5 Hz, H g ); 7.61 (s, IH, H 3 ); 8.26 (d, IH, Jg _=1) ppm. 7-trifluoromethyl-thiokynu- 155-157°C 7.38 (dd, IH, J -_ 5 =9 Hz; J g _ g =1.5 Hz, H- g ); renic acid 7.7 (s, IH, H 3 ); 7.8 (bs, IH, Hg); 8.36 (d, IH, J 5 _ g = 9 Hz, H 5 ) ppm. 7-methoxy-thiokynurenic acid 134-137°C 3.62 (s, 3H, MeO-Ar); 6.88 (bs, IH, H g ); 7.6 (s, IH, H 3 ); 7.76 (d, IH, J 5 _ g = 9 Hz, H g ); 8.21 (d, IH, J 5 _ g = 9 Hz, H 5 ) ppm. 8-chloro-thiokynurenic acid 260-261°C 6.71 (s, IH, H 3 ); 6.97 (t, IH, J g _ 5 =8.4 Hz; J g __ 7 =8.4 Hz, H g ); 7.41 (dd, IH, J ? _ 6 =8.4 Hz; J 7 __ 5 =1.5 Hz, H7); 7.78 (dd, IH, J 5 _ g =8.4 Hz; J,- _=1.5 Hz, H5) ppm. 5-fluoro-thiokynurenic acid 275-277°C 6.53 (s, IH, H 3 ); 6.82 (t, IH, J ? _ g =9 Hz; J 7 _ 8 =9 Hz, H 7 ); 7.1 (dd, IH, J 8 _ 7 = Hz; Jg_ g =2 Hz, H8); 7.81 (dd, IH, J g _ 7 =9 Hz; J g _ 8 =2 Hz, H g ) ppm. 5,7-dichloro-thiokynurenic acid 210-212°C 7.05 (d, IH, J 6 _ 8 =l Hz, H g ) ; 7.38 (d, IH, J g _g=l Hz, H8); 7.75 (s, IH, H 3 ) ppm.

Claims: CLAIMS 1. Compounds of formula I wherein: R is hydroxy or a physiologically acceptable group which may be converted i_n vivo to OH group; R, is hydrogen or a physiologically acceptable group which may be hydrolized in_ vivo to give the free thio group; 2 , R 3 o R. , which are the same or different, are hy¬ drogen, halogen (chlorine, bromine, iodine or fluo¬ rine), £■■ < -£ - alkyl, C,-C 8 alkoxy, C,-C 8 alkylthio, tri- fluoromethyl, nitro, cyano, c - ι - 8 haloalkoxy, c ι ~ c c alkoxycarbonyl, c χ _C 6 ac y hydroxy, c ~ \ ~ c - acyloxy groups. 2. Compounds according to claim 1 wherein R. is hydro¬ gen and R is hydroxy. 3. Compounds according to claim 1 or 2 wherein R_, R, and R 4 are independently selected from hydrogen, halo¬ gen, C,-C 8 alkoxy, trifluoromethyl. 4. A compound according to claim 1 selected from thiokynurenic acid , 7-chloro-thio-kynurenic acid, 6-chloro-thiokynurenic acid, 7-trifluoromethyl-thioky- nurenic acid, 7-methoxy-thiokynurenic acid, 8-chloro- thiokynurenic acid, 5-fluoro-thiokynurenic acid, 5,7- dichloro-thiokynurenic acid. Compounds of formula III as intermediates wherein R 1 , R 2 , R 3 and R. are as defined above. 6. Compounds of formula IV as intermediates wherein R 1 .R 2„, R., and R Λ are as defined above. 7. Pharmaceutical compositions containing as the active principle a compound of formula I in admixture with a suitable excipient. 8. A process form the preparation of compounds I comprising the reaction of compounds of formula II wherein R 2 , R 3 and R. are as defined above and R' is OH or a group which may be converted in hydroxy group, with N,N-dimethylthiocarbamoyl chloride, the subsequent treatment with acids, hydrolysis and optional removal of protective groups. 9 * The use of compounds of claims 1-4 for the prepara- tion of a medicament for the treatment "of neurological disorders.

Inventors: MORONI FLAVIO, PELLICCIARI ROBERTO, MORONI, FLAVIO, PELLICCIARI, ROBERTO
Applicants: MORONI FLAVIO, PELLICCIARI ROBERTO, MORONI, FLAVIO, PELLICCIARI, ROBERTO
Application year: 1990
Main classification: A61K31
IPC codes: A61K31, A61P25, C07D215