Indole derivatives and their use
This is a divisional application of co-pending application Ser. No. 07/645,381, filed Jan. 23, 1991, now U.S. Pat. No. 5,126,363. 
    
    
     This invention is in the field of pharmaceutical agents exhibiting central nervous system (CNS) activities. More specifically, the invention relates to novel indole derivatives, to a process for their preparation, to pharmaceutical compositions comprising the compounds, and to methods of treating therewith. The novel endole derivatives are potentially suitable for counteracting (including preventing, relieving and curing) certain CNS disorders. 
     It has long been known that serotonin (5-hydroxy-tryptamine, hereinafter referred to as 5-HT) is a neurotransmitter in the central nervous system. In particular, over the last decade intensive pharmacological research directed to serotonergic neurotransmitter functions has taken place. It is now generally accepted that in the CNS there are at least five different subtypes of 5-HT binding sites or receptors, which types are identifiable as 5-HT 1A , 5-HT 1B , 5-HT 1C , 5-HT 2  and 5-HT 3 , respectively. Differentiation of the 5-HT receptor subtypes is mainly based on their binding characteristics as characterized by specific radio ligands. For example, the ligand 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) binds with high affinity to 5-HT 1A  receptors, while another ligand, a 2,4(1 H,3 H) -quinazolinedione derivative (adopted name: ketanserin) exhibits high affinity for the 5-HT 2  receptor subtype. It is worth noting that none of these synthetic ligands have any chemical resemblance whatsoever to the physiological binding partner, i.e. 5-HT. For a recent review of 5-HT receptor- ligand interactions reference is made to J.R. Fozard: Trends in Pharmacol.Sci. 8 (1987), 501-506. 
     A variety of endole derivatives which are chemically closer related to 5-HT, such as RU 24969, which is a 3-(tetrahydropyridin-4-yl)-indole (Ann.Reports Med.Chem. 21 (1986), 42-43) have high affinity for 5-HT 1  recognition sites, but generally they show only limited capacity to discriminate between the 5-HT 1A  and 5-HT 1B  receptor subtypes. 
     It has now surprisingly been observed that compounds of the general formula (I) hereinafter bind with high affinity to 5-HT receptors and, furthermore, that some of the compounds exhibit substantially higher affinity the 5-HT 1A  subtype than many of the synthetic ligands known heretofore. Based on their binding specificity these compounds may be classified as extremely potent and specific 5-HT 1A  agonists and, as such, of potential utility for the treatment of disorders associated with serotonergic dysfunctions. Such dysfunctions may be involved in the impairment of thermoregulation, memory function, sleep and satiety control of the consumption of feed and/or beverage, which may include alcohol. They may also play a role in the development of hypertension, hyperemesis, and of such mental states as depression, anxiety or psychosis. 
     Thus the present invention provides novel endole derivatives of the general formula (I): ##STR2## wherein R 1 , R 2 , R 3  and R 4 , which may be the same or different, each is selected from the group consisting of hydrogen; lower alkyl containing from 1 to 4 carbon atoms, in which one or more hydrogen atoms may be substituted by halogen, e.g. CF 3  : OR 7  or --COOR 7  in which R 7  is hydrogen, C 1-4  -alkyl, aryl or aralkyl; halogen, e.g. chlorine; and the group ##STR3## wherein R 8  and R 9  may be the same or different, each representing hydrogen or lower alkyl containing from 1 to 4 carbon atoms; A 1  represents a straight or branched alkylene chain containing from 2 to 4 carbon atoms; R 5  is hydrogen or a straight or branched C 1-5  -alkyl group; A 2  is a straight or branched saturated or unsaturated hydrocarbon chain containing from 2 to 6 carbon atoms; and R 6  is selected from the group consisting of ##STR4## wherein R 10  and R 11 , which may be the same or different, each represents a C 1-3  -alkyl group, or R 10  and R 11  together represent a tetra- or pentamethylene chain, thereby forming together with the heterocyclic ring an azaspiro- decanedione/trione or -undecanedione/trione ring structure; ##STR5## wherein R 12  and R 13 , which may be the same or different, each represents a C 1-3  -alkyl group, or R 12  and R 13  together with their neighbouring carbon atoms form a 5- or 6-membered saturated or nonsaturated ring fused to the 5-membered ring; ##STR6## wherein E is --CH 2  --, --CH 2  --CH 2  --, --CH═CH--, --O-- or --S-- and the dotted line represents optional unsaturation; R 14  and R 15 , which may be the same or different, each represents hydrogen, a C 1-3  -alkyl group, or R 14  and R 15  together with their neighbouring carbon atoms form a cyclopropane, cyclobutane, cyclobutene, cyclohexane or cyclohexene ring fused to the bicyclic ring structure. 
     The compounds of formula I may be converted into any physiological acceptable salts thereof. 
     The invention includes within its scope all optical isomers of compounds of the general formula (I) and their mixtures including racemic mixtures thereof. 
     Compounds of the general formula (I) were tested for binding to 5-HT receptors and compared with known ligands by the following procedure: 
     Rat brain tissue (as specified in the table hereinafter) was homogenized using a Polytron homogenizer. The final pellet was resuspended in 125 vol (tissue wet weight) of buffer. 
     In all assays incubation was carried out for 10 min at 37° C. 
     Labelling of the 5-HT 1B  receptor was complicated by the fact that the available ligand  3  H-5-HT is nonselective. However, by inclusion of the 5-HT 1A  selective agent 8-OH-DPAT in the assay, labelling of the 5-HT 1A  receptor could be avoided and a relatively selective labelling of the 5-HT 1B  receptor could be accomplished. 
     Detailed conditions for the receptor binding assay in vitro are tabulated below. 
     
         __________________________________________________________________________
Receptor type                                                             
         5-HT.sub.1A                                                      
                   5-HT.sub.1B                                            
                              5-HT.sub.2                                  
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Ligand   .sup.3 H-8OH-DPAT                                                
                   .sup.3 H-5-HT                                          
                              .sup.3 H-ketanserin                         
Tissue   frontal cortex                                                   
                   frontal cortex                                         
                              frontal cortex                              
         Hippocampus                                                      
                   Hippocampus                                            
                   striatum                                               
Buffer   50 mM Tris-Citrate                                               
                   50 mM Tris-HCl                                         
                              50 mM Tris-Citrate                          
         (pH 7.4, 30° C.)                                          
                   (pH 7.4, 37° C.)                                
                              (pH 7.4, 30° C.)                     
         120 mM NaCl,                                                     
                   120 mM NaCl, 4 mM                                      
                              120 mM NaCl, 4 mM                           
         4 mM MgCl.sub.2                                                  
                   CaCl.sub.2, 4 mM MgCl.sub.2                            
                              MgCl.sub.2                                  
Centrifugation                                                            
         24,000 × g, twice                                          
                   24,000 × g, twice                                
                              24,000 × g, once                      
Preincubation                                                             
         10 min, 37° C.                                            
                   10 min, 37° C.                                  
                              --                                          
Hemogenization                                                            
         20 ml     20 ml      20 ml                                       
mg tissue/assay                                                           
         10        10         10                                          
Ligand conc.                                                              
         2 nM      1 nM       0.4 nM                                      
Addition to assay                                                         
         --        50 nM 8-OH-DPAT                                        
                              --                                          
Monspec. binding                                                          
         10 μM serotonin                                               
                   10 μM serotonin                                     
                              1 μM cyproheptadine                      
defined with                                                              
Level of nonspec.                                                         
         20-30%    20-25%     12-18%                                      
binding                                                                   
__________________________________________________________________________
 
    
     The following results were obtained: 
     
         ______________________________________                                    
Receptor binding IC.sub.50 (nM)                                           
Compound     5-HT.sub.1A   5-HT.sub.1B                                    
______________________________________                                    
Buspirone    20            above   1000                                   
Gepirone     248           above   1000                                   
Ipsapirone   25            above   1000                                   
8-OH-DPAT    3.4           above   1000                                   
Example 1    26                    480                                    
Example 2    375                   148                                    
Example 4    4             above   1000                                   
Example 5    2.5           above   1000                                   
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     The present invention also provides a process for preparing the compounds of the general formula (I) and physiologically acceptable salts thereof, which process is outlined hereinafter. 
     A compound of the general formula (II) ##STR7## wherein R 1 , R 2 , R 3 , R 4 , and A 1  are as defined for formula (I), and Z represents R 5  of formula (I) or a group convertible into hydrogen (during such an alkylation process the indole nitrogen and any free hydroxy groups in the benzene ring may be protected, e.g. by benzylation), e.g. benzyl, may be reacted with a compound of the general formula 
     
         L--A.sup.2 --R.sup.6                                       (iii) 
    
     wherein L represents a leaving group, of which halogen, in particular bromine, is preferred, and A 2  and R 6  are defined as in connection with formula (I). 
     Many representatives of compounds of formula (II) are commercially available or known from the literature. Other compounds falling within the scope of formula (II) may be prepared by methods, which are generally analogous to those of said literature. General methods for the preparation of compounds of formula 
     
         L--A.sup.2 --R.sup.6 
    
     are described in British Patent Publication 2,174,703A wherefrom by analogy alternative methods for establishing the ##STR8## chain can be derived. 
     The reaction may conveniently be effected in an organic solvent, such as an aprotic solvent, e.g. acetonitrile or dimethylformamide in the presence of a base, for example potassium carbonate. When the leaving group L is different from iodine, being e.g. bromine, the reaction can be conducted in the presence of a salt of hydrogen iodide, e.g. potassium iodide. Usually, the reaction is completed with stirring at a temperature above ambient. The reaction product obtained following, if necessary, after the conversion of Z into hydrogen, may be recovered by conventional means and, if desirable, subjected to purification, e.g. by suitable chromatographic procedures. 
     The purified reaction product may be converted into a physiologically acceptable salt. Such salts include acid addition salts formed with inorganic or organic acids, for example hydrochlorides, hydrobromides, sulphates, nitrates, oxalates, phosphates, tartrates, citrates, fumarates, maleates, succinates, and sulphonates e.g. mesylates. 
     If desirable, selected salts may be subjected to further purification by recrystallization. 
     The compound of the invention, together with a conventional adjuvant, carrier, or diluent, and if desired in the form of a pharmaceutically-acceptable acid addition salt thereof, may be placed into the form of pharmaceutical compositions and unit dosages thereof, and in such form may be employed as solids, such as tablets or filled capsules, or liquids, such as solutions, suspensions, emulsions, elixirs, or capsules filled with the same, all for oral use, in the form of suppositories for rectal administration; or in the form of sterile injectable solutions for parenteral (including subcutaneous) use. Such pharmaceutical compositions and unit dosage forms thereof may comprise conventional ingredients in conventional proportions, with or without additional active compounds or principles, and such unit dosage forms may contain any suitable effective central nervous system ailment alleviating amount of the active ingredient commensurate with the intended daily dosage range to be employed. Tablets containing one (1) milligram of active ingredient or, more broadly, one (1) to thirty (30) milligrams, per tablet, are accordingly suitable representative unit dosage forms. 
     The compounds of this invention can thus be used for the formulation of pharmaceutical preparations, e.g., for oral and parenteral administration to mammals including humans, in accordance with conventional methods of galenic pharmacy. 
     Conventional excipients are such pharmaceutically acceptable organic or inorganic carrier substances suitable for parenteral or oral application which do not deleteriously react with the active compound. 
     Examples-of such carriers are water, salt solutions, alcohols, polyethylene glycols, polyhydroxyethoxylated castor oil, gelatin, lactose, amylose, magnesium stearate, talc, silicic acid, fatty acid monoglycerides and diglycerides, pentaerythritol gatty acid esters, hydroxymethylcellulose and polyvinylpyrrolidone. 
     The pharmaceutical preparations can be sterilized and mixed, if desired, with auxilliary agents, such as lubricants, preservatives, stabilizers, wetting agents, emulsifiers, salt for influencing osmotic pressure, buffers and/or coloring substances and the like, which do not deleteriously react with the active compound. 
     For parenteral application, particularly suitable are injectable solutions or suspensions, preferably aqueous solutions with the active compound dissolved in polyhydroxylated castor oil. 
     Ampoules are convenient unit dosage forms. 
     For oral-application, particularly suitable are tablets, dragees, or capsules having talc and/or a carbohydrate carrier or binder or the like, the carrier preferably being lactose and/or corn starch and/or potato starch. A syrup, elixir or like can be used when a sweetened vehicle can be employed. Generally, as to broader ranges, the compound of the invention is dispensed in unit dosage form comprising 0.05-100 mg in a pharmaceutically-acceptable carrier per unit dosage. 
     A typical tablet which may be prepared by conventional tabletting techniques contains: 
     
         ______________________________________                                    
Active compound    1.0    mg                                              
Lactosum           67.8   mg Ph. Eur.                                     
Avicel             31.4   mg                                              
Amberlite IRP 88   1.0    mg                                              
Magnesii stearas   0.25   mg Ph. Eur.                                     
______________________________________                                    
 
    
     Due to their high degree of affinity for the 5-HT receptors, the compounds of the invention are extremely useful in the treatment of central nervous system ailments or disorders, when administered in an amount effective for the alleviation, amelioration, or elimination thereof. The important CNS activity of the compounds of the invention as mentioned above, along with a low toxicity, together presenting a most favorable therapeutic index. The compounds of the invention may accordingly be administered to a subject, e.g., a living animal body, including a human, in need of the same for the treatment, alleviation, amelioration, or elimination of an indication, associated with the central nervous system and the 5-HT receptors, which requires such psychopharmaceutical treatment, if desired in the form of a pharmaceutically acceptable acid addition salt thereof (such as the hydrobromide, hydrochloride, or sulfate, in any event prepared in the usual or conventional manner, e.g., evaporation to dryness of the free base in solution together with the acid), ordinarily concurrently, simultaneously, or together with a pharmaceutically-acceptable carrier or diluent, especially and preferably in the form of a pharmaceutical composition thereof, whether by oral, rectal, or parenteral (including subcutaneous) route, in an effective psychopharmaceutical central nervous system ailment alleviating amount, and in any event an amount which is effective for the alleviation of such a central nervous system ailment due to their 5-HT receptor affinity. Suitable dosage ranges are 1-200 milligrams daily, 1-100 milligrains daily, and especially 1-30 milligrams daily, depending as usual upon the exact mode of administration, form in which administered, the indication toward which the administration is directed, the subject involved and the body weight of the subject involved, and the preference and experience of the physician or veterinarian in charge. 
     The following examples serve to illustrate the present invention. 
    
    
     EXAMPLE 1 
     1-(4-(1,3-Dioxo-4,7-etheno-1,3,3a,4,4a,6a,7,7a-octahydro -2 H-cyclobut[f]isoindol-2-yl)butyl-1-amino)-2-(3-indolyl)-ethane, oxalate 
     A mixture of tryptamine (480 mg; 3.0 mmol), 2-(4-bromobutyl) -1,3-dioxo-4,7-etheno-1,3,3a,4,4a,6a,7,7a-octahydro- 2 H-cyclobut[f]isoindole (Abou-Gharbia et al., J. Med. Chem. 1988, 31, 1382-1392) (1.0 g; 3.0 mmol), potassium carbonate (830 mg; 6.0 mmol) in acetonitrile (20 ml) was stirred and heated at 60° C. for 40 h. The solvent was removed under reduced pressure. Ethyl acetate (30 ml) was added to the residue followed by water (30 ml) and the organic phase was separated. The aqueous phase was extracted with ethyl acetate (2×30 ml) and the combined organic phases were dried (MGSO 4 ), filtered and evaporated to give an oil, which was flash-chromatographed on silica gel 60 with ethyl acetate graduated to ethyl acetate/reethanol 4:1. The title compound was isolated as the oxalate. M.p. 209°-210° C. Ms (70 eV): m/z 416 (2%, M+1) 415 (2%, M + ), 285 (100), 256 (7), 214 (4), 130 (27). 
     EXAMPLE 2 
     1-(4-Phthalimidobutyl-1-amino)-2-(3-indolyl)-ethane, oxalate 
     A mixture of tryptamine (1.28 g; 8.0 mmol), N-(4-bromobutyl)phthalimide (2.25 g; 8.0 mmol), potassium carbonate (2.2 g; 16 mmol) in acetonitrile (60 ml) was stirred and heated at 60° C. for 40 h. The solvent was removed under reduced pressure. Ethyl acetate (75 ml) was added to the residue followed by water (75 ml) and the organic phase was separated. The aqueous phase was extracted with ethyl acetate (2×75 ml) and the combinlit ed organic phases were dried (MGSO 4 ), filtered and evaporated to give an oil, which was flashchromatographed on silica gel 60 with ethyl acetate. The title compound was isolated as the oxalate. M.p. 215°-218° C. MS (70 eV): m/z 362 (2%, M+1), 361 (1%, M + ), 231 (100), 202 (8), 160 (30), 130 (31). 
     EXAMPLE 3 
      1-(4-(Cis-4-cyclohexen-1,2-dicarboximido)butyl-1amino)-2-(3-indolyl)-ethane, oxalate 
     A mixture of tryptamine (620 mg; 3.9 mmol), N-(4-bromobutyl) -cis-4-cyclohexen-1,2-dicarboximide (1.1 g; 3.9 mmol), potassium carbonate (1.1 g; 8.0 mmol) in acetonitrile (30 ml) was stirred and heated at 60° C. for 40  h. The solvent was removed under reduced pressure. Ethyl acetate (50 ml) was added to the residue followed by water (50 ml) and the organic phase was separated. The aqueous phase was extracted with ethyl acetate (2×50 ml) and the combined organic phases were dried (MgSO 4 ), filtered and evaporated to give an oil, which was flashchromatographed on silica gel 60 with ethyl acetate. The title compound was isolated as the oxalate. M.p. 166°-167° C.  1  H NMR (DMSO+D 2  O, 400 MHz) 7.60-6.95 (m, 5 H), 5.85 (m, 2 H), 3.35 (m, 2 H), 3.20-3.10 (m, 4 H), 3.10-3.00 (m, 2 H), 3.00-2.90 (m, 2 H), 2.45-2.10 (m, 4 H), 1.50 (m, 4 H). 
     EXAMPLE 4 
     1-(4-(7,9-Dioxo-8-azaspiro[4,5]decan-8-yl)butyl-1-amino)-2-(5-methoxy-3-indolyl)-ethane, oxalate 
     A mixture of 5-methoxytryptamine, hydrochloride (500 mg; 2.2 mmol), 8-(4-bromobutyl)-8-azaspiro[4,5]decane7,9-dione (665 mg; 2.2 mmol), potassium carbonate (550 mg; 40 mmol) in acetonitrile (20 ml) was stirred and heated at 60° C. for 40 h. The solvent was removed under reduced pressure. Ethyl acetate (30 ml) was added to the residue followed by water (30 ml) and the organic phase was separated. The aqueous phase was extracted with ethyl acetate (2×30 ml) and the combined organic phases were dried (MGSO 4 ), filtered and evaporated to give an oil, which was flashchromatographed on silica gel 60 with ethyl acetate graduated to ethyl acetate/reethanol (4:1). The title compound was isolated the oxalate. M.p. 109.5°-110° C.  1  H NMR (DMSO+D 2  O, 400 MHz) 7.30-6.70 (m, 4 H), 3.75 (s, 3 H), 3.60 (m, 2 H), 3.15-3.05 (m, 2 H), 3.00-2.90 (m, 4 H), 2.60 (s, 4 H), 1.65-1.35 (m, 12 H). 
     EXAMPLE 5 
     1-(4-(1,3-Dioxo-4,7-etheno-1,3,3a,4,4a,6a,7,7a-octa-hydro -2 H-cyclobut(f]isoindol-2-yl)butyl-1-amino)-2(5-methoxy-3-indolyl)-ethand, oxalate 
     A mixture of 5-methoxytryptamine, hydrochloride (500 mg; 2.2 mmol), 2-(4-bromobutyl)-1,3-dioxo-4,7-etheno1,3,3a,4,4a,6a,7,7a-octahydro-2 H-cyclobut(f]isoindole (740 mg; 2.2 mmol), potassium carbonate (550 mg; 4.0 mmol) in acetonitrile (20 ml) was stirred and heated at 60° C. for 16 h. The solvent was removed under reduced pressure. Ethyl acetate (30 ml) was added to the residue followed by water (30 ml) and the organic phase was separated. The aqueous phase was extracted with ethyl acetate (2×30 ml) and the combined organic phases were dried (MgSo 4 ), filtered and evaporated to give an oil, which was flashchromatographed on silica gel 60 with ethyl acetate graduated to ethyl acetate/methanol (4:1). The title compound was isolated as the oxalate. M.p. 122°-123° C. MS (70 eV): m/z 445 (14, M + ), 285 (100), 256 (7), 174 (6), 160 (28), 146 (4). 
     EXAMPLE 6 
     4-(7,9-Dioxo-8-azaspiro[4,5]decan-8-yl)butyl-2-3-indolyl)ethyl-methylamine, oxalate 
     A mixture of 3-(2-methylaminoethyl)indole (1.0 g, 5.7 mmol), 8-(4-bromobutyl)-8-azaspiro[4,5]decane-7,9-dione (1.7 g, 5.7 mmol) and potassium carbonate (1.4 g, 10 mmol) was stirred and refluxed for 8 h and then concentrated in vacuo. The residue was dissolved in water and extracted with ethyl acetate (three times). The combined organic phases were dried over MgSO 4  and evaporated to give an oil, which was flash chromatographed on silica 60 with ethyl acetate. The product was dissolved in acetone and oxalic acid (500 mg in 5 ml acetone) added to precipitate the desired product. M.p. &gt;80° C., dec. MS (70 eV): m/z 396 (24, M+I), 395 (m + , 1%), 265 (100%), 222 (17%), 180 (5%), 130 (30%).