Hexahydrodibenzo[a,g]quinolizine compound, preparation method thereof, pharmaceutical composition and use thereof

Abstract

The present invention relates to a novel hexahydrodibenzo[a,g]quinoline compound represented by general formula (I) and its derivatives, enantiomer, diastereoisomer, raceme and mixtures thereof, as well as pharmaceutically acceptable salts thereof. The present invention further relates to a method for preparing the compound, and the compound has good prevention and treatment effect on neurological diseases, especially diseases associated with dopamine receptor and 5-hydroxytryptamine receptor. The bioactivity experiment demonstrates that, the compound is expected to be developed into a novel and potent chemical entity for treating diseases associated with dopamine receptor and 5-hydroxytryptamine receptor, especially schizophrenia, Parkinson's disease, drug addiction, migraine and so on.

1 . A hexahydrodibenzo[a,g]quinoline compound of general formula (I): 
       
         
           
           
               
               
           
         
         an enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof, 
         wherein R 2  is a hydroxy, a hydroxy-substituted C1-C6 alkyl, a substituted or unsubstituted C1-C6 alkoxy, a halogen, a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C2-C6 alkynyl, a substituted or unsubstituted C3-C6 cycloalkyl, a substituted or unsubstituted C1-C6 alkanoyl, a substituted or unsubstituted C6-C20 aryl, a substituted or unsubstituted benzyl, an amino acid or N-protected amino acid, or —(CO) R 9 ; 
         when R 2  is a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C1-C6 alkoxy, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C2-C6 alkynyl, or a substituted or unsubstituted C3-C6 cycloalkyl, a substituent for substitution can be a halogen or COOR 10 ; 
         when R 2  is a substituted or unsubstituted C1-C6 alkanoyl, a substituted or unsubstituted C6-C20 aryl, or a substituted or unsubstituted benzyl, a substituent for substitution is selected from the following group: C1-C6 alkyl, a halogen, C1-C6 alkoxy; 
         wherein R 9  is a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C2-C6 alkynyl, a substituted or unsubstituted C6-C20 aryl, or heteroaryl selected from thiazolyl, pyrazolyl, imidazolyl, thienyl, furyl, pyrrolyl, or pyridyl; 
         when R 9  is a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, or a substituted or unsubstituted C2-C6 alkynyl, a substituent for substitution is a carboxyl, a substituted or unsubstituted C6-C20 aryl, or heteroaryl selected from thiazolyl, pyrazolyl, imidazolyl, thienyl, furyl, pyrrolyl, or pyridy; 
         when R 9  is a substituted or unsubstituted C6-C20 aryl, a substituent for substitution is a C1-C6 alkyl, a halogen or a C1-C6 alkoxy; R 10  is H, a C6-C20 alkyl substituted or unsubstituted C1-C6 alkyl, a C2-C6 alkenyl, or a C2-C6 alkynyl; when R 2  is an amino acid or N-protected amino acid, the amino acid can be D-amino acid, L-amino acid or racemate; 
         each of R 3 , R 4  is independently H, a halogen substituted or unsubstituted C1-C6 alkyl, a halogen substituted or unsubstituted C1-C6 alkoxy, a C2-C6 alkenyl, a C2-C6 alkynyl, a halogen, COOR 11 , or CONR 12 R 13 , wherein R 11  is H, a substituted or unsubstituted C1-C6 alkyl, a C2-C6 alkenyl, a C2-C6 alkynyl, a substituted or unsubstituted C6-C20 aryl, or a substituted or unsubstituted benzyl; when R 11  is a substituted or unsubstituted C6-C20 aryl, or a substituted or unsubstituted benzyl, a substituent for substitution is a C1-C6 alkyl, a halogen or a C1-C6 alkoxy; when R 11  is a substituted or unsubstituted C1-C6 alkyl, a substituent for substitution is a halogen; each of R 13 , R 12  is independently H, a substituted or unsubstituted C1-C6 alkyl or they and nitrogen atom together form azetidine, pyrrolidinyl, piperazinyl, or morpholinyl, when R 13  or R 12  is a substituted or unsubstituted C1-C6 alkyl, a substituent for substitution is a halogen; 
         each of R 1 , R 5 , R 6 , R 7 , R 8  is independently H, a hydroxy, a hydroxy-substituted C1-C6 alkyl, a halogen-substituted or unsubstituted C1-C6 alkyl, a halogen substituted or unsubstituted C1-C6 alkoxy, a halogen, a C3-C6 cycloalkyl, a halogen substituted or unsubstituted C2-C6 alkenyloxy, a halogen-substituted or unsubstituted C3-C6 alkynyloxy, a substituted or unsubstituted benzyloxy, a substituted or unsubstituted C6-C20 aryl, R 14 COO—, R 15 R 16 N—; when R 1 , R 5 , R 6 , R 7 , or R 8  is a substituted or unsubstituted benzyloxy, or a substituted or unsubstituted C6-C20 aryl, a substituent for substitution is a C1-C6 alkyl, a halogen, or a C1-C6 alkoxy; wherein R 14  is H, a halogen-substituted or unsubstituted C1-C6 alkyl; each of R 15  and R 16  is independently selected from H, a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, or a substituted or unsubstituted C2-C6 alkynyl or they and nitrogen atom together form azetidine, pyrrolidinyl, piperazinyl, or morpholinyl, when R 15  or R 16  is a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C2-C6 alkynyl, a substituent for substitution is a C1-C6 alkyl, a halogen or a C1-C6 alkoxy; 
         R 1  and R 2  can together form a substituted or unsubstituted 5-7 membered heterocycle, a substituent for substitution is a halogen, or a halogen-substituted or unsubstituted C1-C6 alkyl, C2-C6 alkenyl, or C2-C6 alkynyl; and the heterocycle contains 1-3 heteroatom(s) selected from N, O or S; 
         any two adjacent substituents of R 5 , R 6 , R 7  and R 8  can together form a substituted or unsubstituted 5-7 membered heterocycle, a substituent for substitution is a halogen, or a halogen-substituted or unsubstituted C1-C6 alkyl, C2-C6 alkenyl, or C2-C6 alkynyl; and the heterocycle contains 1-3 heteroatom(s) selected from N, O or S; and 
         the configuration of chiral carbon atom in the compound of general formula (I) is R or S configuration, 
         provided that when the compound of general formula (I) is racemate: 
         (a) when R 2  is methoxyl, R 3  is H, R 4  is H or methyl, and at least one of R 5 , R 6 , R 7 , and R 8  is methoxyl or R 6  and R 7  together form —O—CH 2 —O—, then R 1  is not H, methoxyl or BnO; 
         (b) when R 1  and R 2  together form —O—CH 2 —O—, and R 7  or R 8  is methoxyl, then R 5  is not methoxyl; 
         (c) when R 6  and R 7  together form —O—CH 2 —O— and R 5  and R 8  are H, then R 2  is not methoxyl and R 1  and R 2  together do not form —O—CH 2 —O—; and 
         (d) the compound of general formula (I) is not DC037027, 
       
       
         
           
           
               
               
           
         
       
     
     
         2 . The hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 1 ,
 wherein R 1  is H, a halogen-substituted or unsubstituted C1-C6 alkyl, a halogen-substituted or unsubstituted C1-C6 alkoxy, a hydroxy, a hydroxy-substituted C1-C6 alkyl or a halogen-substituted or unsubstituted benzyloxy; R 2  is a hydroxy, a hydroxy-substituted C1-C6 alkyl, a halogen substituted or unsubstituted C1-C6 alkyl, a halogen substituted or unsubstituted C1-C6 alkoxy, or a halogen; R 3  is H, or a halogen substituted or unsubstituted C1-C6 alkyl; R 4  is H, a halogen substituted or unsubstituted C1-C6 alkyl, or a halogen substituted or unsubstituted C1-C6 alkoxy; R 5  is H, a halogen substituted or unsubstituted C1-C6 alkyl, a halogen substituted or unsubstituted C1-C6 alkoxy or a halogen; R 6  is H, a halogen-substituted or unsubstituted C1-C6 alkyl, a halogen-substituted or unsubstituted C1-C6 alkoxy, a hydroxy, or a hydroxy-substituted C1-C6 alkyl; R 7  is H, a halogen-substituted or unsubstituted C1-C6 alkyl, a halogen-substituted or unsubstituted C1-C6 alkoxy, a hydroxy, or a hydroxy-substituted C1-C6 alkyl; R 8  is H, a hydroxy, a hydroxy-substituted C1-C6 alkyl, a halogen-substituted or unsubstituted C1-C6 alkoxy, a halogen-substituted or unsubstituted C1-C6 alkyl or a halogen;   or R 1  and R 2  can together form a C1-C6 alkyl-substituted or unsubstituted 5-7 membered heterocycle, and the heterocycle contains 1-2 heteroatom(s) selected from N, O or S;   R 6  and R 7  can together form a fluoro-, chloro- or bromo-substituted 5-7 membered heterocycle, and the heterocycle contains 1-2 heteroatom(s) selected from N, O or S.   
     
     
         3 . The hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 2 ,
 wherein R 1  is H, a C1-C6 alkyl, a C1-C6 alkoxy, a hydroxy, a hydroxy-substituted C1-C6 alkyl or benzyloxy; R 2  is a hydroxy, a hydroxy-substituted C1-C6 alkyl, a C1-C6 alkyl, a C1-C6 alkoxy or a halogen; R 3  is H or a C1-C6 alkyl; R 4  is H, a C1-C6 alkyl, or a C1-C6 alkoxy; R 5  is H, a C1-C6 alkyl, a C1-C6 alkoxy or a halogen; R 6  is H, a C1-C6 alkyl, a C1-C6 alkoxy, a hydroxy, or a hydroxy-substituted C1-C6 alkyl; R 7  is H, a C1-C6 alkyl, a C1-C6 alkoxy, a hydroxy, or a hydroxy-substituted C1-C6 alkyl; R 8  is H, a hydroxy, a hydroxy-substituted C1-C6 alkyl, a C1-C6 alkoxy, a C1-C6 alkyl or a halogen; the halogen is F, Br or Cl;   R 1  and R 2  can together form a C1-C6 alkyl-substituted or unsubstituted 5- or 6-membered heterocycle and the heterocycle contains 1-2 heteroatom(s) selected from N, O or S;   R 6  and R 7  can together form a fluoro-, chloro- or bromo-substituted or unsubstituted 5- or 6-membered heterocycle and the heterocycle contains 1-2 heteroatom(s) selected from N, O or S.   
     
     
         4 . The hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 1 ,
 wherein, the configuration of chiral C atom which is not linked with R 3  or R 4  in the parent nucleus of compound of general formula (I) is S.   
     
     
         5 . The hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 1 ,
 wherein, the configuration of chiral C atom which is not linked with R 3  or R 4  in the parent nucleus of compound of general formula (I) is R.   
     
     
         6 . The hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 1 ,
 wherein, the compound of general formula (I) is chiral compound.   
     
     
         7 . The hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 1 ,
 wherein, R 5  is methoxyl, and R 6  is hydroxyl.   
     
     
         8 . The hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 1 ,
 wherein, R 3  is a halogen substituted or unsubstituted C1-C6 alkyl, a halogen substituted or unsubstituted C1-C6 alkoxy, a C2-C6 alkenyl, a C2-C6 alkynyl, a halogen, COOR 11 , or CONR 12 R 13 .   
     
     
         9 . The hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 1 ,
 wherein, R 8  is a hydroxy-substituted C1-C6 alkyl, or a halogen.   
     
     
         10 . The hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 1 ,
 wherein, one to four of R 5 , R 6 , R 7 , and R 8  is a hydroxy-substituted C1-C6 alkyl or C1-C6 alkyl.   
     
     
         11 . The hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 1 , wherein the compound is selected from the group consisting of: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
         12 . A pharmaceutical composition comprising a therapeutically effective amount of the hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, racemate, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 1 , and one or more pharmaceutically acceptable carriers. 
     
     
         13 . A method of treating a nervous system disease relating to dopamine receptors and serotonin receptors in a subject in need thereof, comprising administering to the subject the pharmaceutical composition according to  claim 12 . 
     
     
         14 . The method according to  claim 13 , wherein the nervous system disease is Parkinson's disease, schizophrenia, drug addiction, or migraine. 
     
     
         15 . A preparation method of hexahydro-dibenzo[a,g]quinoline compound according to  claim 1 , wherein the definitions of R1-R4 and R8 are described above, when each of R5 and R6 is independently a halogen-substituted or unsubstituted C1-C6 alkoxy, a substituted or unsubstituted benzyloxy, and R7 is H; or when R5 is a halogen-substituted or unsubstituted C1-C6 alkoxy, a substituted or unsubstituted benzyloxy, R6 is a hydroxy, and R7 is H, the compounds are prepared according to the second reaction route; other compounds are prepared according to the first reaction route; wherein, a substituent for substitution is a C1-C6 alkyl, a halogen or a C1-C6 alkoxy:
 the first reaction route:   
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         reagents and reaction conditions: a) acetic acid, nitromethane, ammonium acetate, 80° C.; b) lithium aluminum hydride, anhydrous tetrahydrofuran, reflux; c) ammonium formate, anhydrous methanol, palladium carbon, hydrogen, room temperature; d) 1-ethyl-3-(3-dimethylpropylamine) carbodiimide, anhydrous dichloromethane, triethylamine, room temperature; e) nitrogen protection, phosphorus oxychloride, acetonitrile, reflux; and f) catalyst (Noyori), N, N-dimethylformamide, triethylamine/formic acid or sodium borohydride; g) aldehyde, acid conditions; 
         the preparation of Compound 2a: a substrate is dissolved in an appropriate amount of glacial acetic acid, to which 1.2-2.0 equivalent of ammonium acetate is added to form a mixture, 5-10 equivalent of nitromethane is added to the mixture at room temperature and reacted in an oil bath, and then the reaction system is cooled to room temperature and a large amount of solid is precipitated, Compound 2a is obtained by suction filtration; 
         the preparation of Compound 3a: lithium aluminum hydride is suspended in an appropriate amount of anhydrous tetrahydrofuran and placed in an ice water bath; a solution of unsaturated nitro-compound 2a in anhydrous tetrahydrofuran is slowly added dropwise; after the addition is completed, the reaction solution is transferred into an oil bath, refluxed, and then cooled to room temperature, then the defined amount of water is added slowly and a clear solution is obtained by filtration, after dried over anhydrous sodium sulfate and evaporated to dryness, an oily Compound 3a is obtained; 
         the preparation of Compound 5a: a substrate 4a is dissolved in an appropriate amount of anhydrous methanol, and 1.5-3.0 equivalent of ammonium formate is added; 10% palladium carbon is added under stirring and hydrogen is ventilated at the same time; the reaction is carried out at room temperature overnight; after the palladium carbon is removed by filtration, the solution is evaporated to dryness to give an oily Compound 5a; 
         the preparation of Compound 6a: at room temperature, the substrate 3a or 5a is condensed with R5-, R6-, R7-, and R8-substituted phenylacetic acid in the presence of 1-ethyl-3(3-dimethyl-propylamine) carbodiimide or triethylamine, and anhydrous dichloromethane, then the product is purified by column chromatography or recrystallized by using ethanol to give Compound 6a; 
         the preparation of Compound 7a: under N 2 , the substrate 6a in acetonitrile used as solvent is refluxed under the action of phosphorus oxychloride to obtain Compound 7a; 
         the preparation of Compound 8a: Compound 7a is reduced by sodium borohydride to form racemic Compound 8a; or catalyst Noyori as the chiral reducing reagent, N,N-dimethylformamide, triethylamine/formic acid are used to carry out the asymmetric reduction reaction, thereby obtaining Compound 8a with a single configuration; 
         the preparation of Compound 9a: the intermediate Compound 8a is reacted with aldehyde under acidic condition to obtain Compound 9a; 
         the second reaction route: 
       
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         wherein R9′ is a C1-C6 alkyl, R5′ is a halogen-substituted or unsubstituted C1-C6 alkyl, or a substituted or unsubstituted benzyl, R6′ is a halogen-substituted or unsubstituted C1-C6 alkyl, or a substituted or unsubstituted benzyl, wherein a substituent for substitution is a C1-C6 alkyl, a halogen or a C1-C6 alkoxy; 
         reaction reagents and conditions: a) room temperature, acetic acid, liquid bromine; b) alkylating reagent/benzylating reagent, solvent, organic alkali/inorganic alkali; c) catalyst containing copper or copper ion, alkaline condition, water, 90° C. to 150° C. of reaction temperature, pH 1-3; d) phenylboronic acid, toluene, paraformaldehyde and water; e) solvent, alkylating reagent/benzylating reagent, organic alkali/inorganic alkali; f) nitrating reagent; g) phenethylamine containing at least one electron-donating substituent, ethanol, reflux; h) solvent, acylating reagent, inorganic/organic alkali; i) solvent, condensing agent; j) sodium borohydride, sodium cyanoborohydride or sodium acetoxy borohydride/catalyst (Noyori), N, N-dimethylbenzamide, triethylamine and formic acid; k) solvent, inorganic alkali; l) solvent, halogenating reagent, organic/inorganic alkali; m) reflux, concentrated hydrochloric acid, ethanol/BCl 3 , dichloromethane; 
         the preparation of Compound 10a: at room temperature, Compound 1b is reacted with liquid bromine to obtain product Compound 10a; 
         the preparation of Compound 11a: under the action of organic/inorganic alkali, Compound 10a is reacted with an alkylating reagent or a benzylating reagent in solvent to obtain Compound 11a, wherein said solvent can be selected from the following group: methanol, ethanol, acetone, N, N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, dichloromethane, chloroform, dioxane; said alkylating reagent is dimethyl sulfate, methyl iodide, diazomethane, or trifluoro methyl sulfonic acid methyl ester; said benzylating reagent is a alkoxy-, alkyl-, nitro- or halogen-substituted benzyl chloride or benzyl bromide; said inorganic alkali is selected from the following group: sodium hydroxide, potassium hydroxide, cesium hydroxide, barium hydroxide, potassium hydride, sodium hydride, sodium tert-butoxide, potassium tert-butoxide, potassium carbonate, sodium carbonate and calcium carbonate; and said organic alkali is selected from triethylamine, diisopropylethylamine, pyridine, N, N-dimethylaniline, N, N-dimethyl-pyridine; 
         the preparation of Compound 12a: a catalyst used in the reaction is one or two of the followings: copper sulfate, copper oxide, copper powder, copper chloride, copper bromide, copper iodide, copper carbonate, copper nitrate, copper hydroxide and the like; the reaction is conducted in the presence of alkali, such as sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium hydroxide, barium hydroxide or quaternary ammonium hydroxide; the reaction can be, but not necessarily, finished with the help of microwave, the reaction temperature is between 90° C. and 150° C.; and Compound 12a can be obtained by adjusting the pH value of reaction mixture to 1-3 after the reaction is finished; 
         the preparation of Compound 13a: 2.0-3.0 equivalent of phenylboronic acid is refluxed in toluene, and then paraformaldehyde is added and reacted in toluene; the solvent is evaporated and the reaction is conducted in water; the reaction mixture is extracted with dichloromethane; then the extract liquid is dried over sodium sulfate and the solvent is evaporated; after stirred in diethyl ether, Compound 13a is obtained by filtration; 
         the preparation of Compound 14a: Compound 13a is reacted with an alkylating reagent, an acylating reagent or a benzylating reagent in a solvent under the action of organic/inorganic alkali to obtain Compound 14a; said solvent is selected from the following group: methanol, ethanol, acetone, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, dichloromethane, chloroform, and dioxane; said alkylating reagent is dimethyl sulfate, methyl iodide, diazomethane, or methyl trifluoromethanesulfonate; said acylating reagent is acetyl chloride, acetic anhydride, benzoyl chloride, trifluoroacetic acid anhydride; said benzylating reagent is alkoxy-, alkyl-, nitro-, or halogen-substituted benzyl chloride or benzyl bromide; said inorganic alkali is selected from sodium hydroxide, potassium hydroxide, cesium hydroxide, barium hydroxide, potassium hydride, sodium hydride, sodium tert-butoxide, potassium tert-butoxide, potassium carbonate, sodium carbonate or calcium carbonate; and said organic alkali is selected from triethylamine, diisopropylethylamine, pyridine, N,N-dimethylaniline, or N, N-dimethyl-pyridine; 
         the preparation of Compound 15a: under the action of a nitrating reagent, Compound 15a, nitration product, is obtained from Compound 14a; the reaction temperature is between 0° C. and 25° C., and the reaction time is 10 minutes to 12 hours; said nitrating reagent is a mixture of concentrated sulfuric acid and nitric acid, a mixture of nitric acid, sodium nitrate and concentrated sulfuric acid, a mixture of concentrated sulfuric acid and potassium nitrate, a mixture of concentrated sulfuric acid and sodium nitrite, or a mixture of acetic acid and concentrated nitric acid; 
         the preparation of Compound 16a: Compound 15a with the same equivalent of phenylethylamine are added to an appropriate amount of ethanol and refluxed overnight; ethanol is evaporated and the crude product is recrystallized in a recrystallization solvent; said recrystallization solvent is selected from one or two of the followings: ethyl acetate, n-hexane, benzene, toluene, petroleum ether, ethanol, isopropanol, methanol, chloroform, and xylene; 
         the preparation of Compound 17a: Compound 16a is dissolved in solvent and organic/inorganic alkali is added; an acylating agent is slowly added at 0° C.; then the reaction proceeded at room temperature and water is added; the reaction mixture is extracted with dichloromethane and dichloromethane layer is washed with saturated saline solution; the extract liquid is dried over sodium sulfate and evaporated to dryness, thereby obtaining Compound 17a; wherein said acylating agent is acetic anhydride, acetyl chloride, trifluoroacetic anhydride, trichloroacetic anhydride, methyl chloroformate, or ethyl chloroformate; said organic alkali is triethylamine, diisopropyl ethylamine, pyridine, N,N-dimethylaniline, or N,N-dimethyl pyridine; and said inorganic alkali is potassium carbonate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, or potassium hydroxide; 
         the preparation of Compound 18a: Compound 17a is dissolved in a solvent and heated to reflux; a condensing reagent is added to the reaction solution; the reaction is monitored by TLC; most of solvent is evaporated, and the reaction solution is neutralized with saturated sodium bicarbonate, extracted for three times with dichloromethane, dried over sodium sulfate and evaporated to dryness; and the product is directly used in next reaction without further purification; wherein said solvent is anhydrous acetonitrile, anhydrous toluene, or benzene; and said condensing reagent is phosphorus oxychloride, phosphorus oxybromide, or phosphorus pentoxide; the preparation of Compound 19a: the imine Compound 18 obtained above is asymmetrically reduced by using Noyori catalyst in anhydrous N,N-dimethylformamide in the presence of triethylamine and formic acid to obtain chiral amine 19a; the reaction is carried out at room temperature for 7 to 12 hours; after the reaction is finished, the reaction solution is neutralized with saturated aqueous sodium bicarbonate solution, extracted with ethyl acetate, and dried over sodium sulfate; or the achirality reduction is conducted by using sodium borohydride, sodium cyanoborohydride or sodium acetoxy borohydride; 
         the preparation of Compound 20a: Compound 19a is dissolved in a solvent and an inorganic alkali is added to above solution, then the reaction is conducted at room temperature and solid precipitates, and the precipitate is filtered and dried, thereby obtaining the target Compound 20a, wherein said inorganic alkali is sodium hydroxide, potassium hydroxide, cesium hydroxide or potassium carbonate; said solvent may be a mixture of water and one of ethanol, methanol, N,N-dimethylformamide; 
         the preparation of Compound 21a: in a solvent, Compound 20a is halogenated with a halogenating agent under alkaline condition, and then product 21a is obtained through ring-closing reaction, wherein said halogenating agent is thionyl chloride, thionyl bromide, phosphorus trichloride, phosphorus tribromide, phosphorus pentachloride, or phosphorus pentabromide; said solvent is dichloromethane, tetrahydrofuran, diethyl ether, or chloroform; said alkaline condition is an organic alkali or an inorganic alkali, wherein the organic alkali is triethylamine, pyridine, diisopropylethylamine, or the inorganic alkali is potassium carbonate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, calcium carbonate, or ammonia; 
         the preparation of Compound 22a: Compound 21a is dissolved in ethanol and concentrated hydrochloric acid is added to reflux or BCl 3  and dichloromethane is added to reflux at low temperature in order to remove R6′ protective group to give Compound 22a. 
       
     
     
         16 . The preparation method according to  claim 15 , wherein, in the second reaction route:
 for the preparation of Compound 11a, said solvent is acetone, N, N-dimethylformamide, or tetrahydrofuran; and said organic alkali is benzyl chloride, benzyl bromide, methyl iodide, dimethyl sulfate or potassium carbonate;   for the preparation of Compound 12a, the catalyst is one or two of the followings: copper sulfate, copper oxide, copper powder; and said alkaline condition is sodium hydroxide, potassium hydroxide, or cesium hydroxide;   for the preparation of Compound 14a, the solvent is acetone, tetrahydrofuran, or N,N-dimethylformamide; said alkylating reagent is dimethyl sulfate, or methyl iodide; said acylating reagent is acetyl chloride, or acetic anhydride; and said inorganic alkali is potassium carbonate;   for the preparation of Compound 15a, said nitrating reagent is a mixture of acetic acid and concentrated nitric acid;   for the preparation of Compound 16a, said solvent for recrystallization is toluene, ethanol, or xylene;   for the preparation of Compound 17a, said acylating agent is acetic anhydride, or acetyl chloride; said organic alkali is triethylamine, diisopropyl ethylamine, or pyridine; and said solvent is dichloromethane, tetrahydrofuran, diethyl ether, or toluene;   for the preparation of Compound 18a, said condensing reagent is phosphorus oxychloride, and said solvent is anhydrous acetonitrile;   for the preparation of Compound 20a, said inorganic alkali is sodium hydroxide and said solvent is a mixture of water and ethanol or methanol; and   for the preparation of Compound 22a, ethanol or concentrated hydrochloric acid is used to remove R6′ protective group.   
     
     
         17 . A substantially optically pure hexahydrodibenzo[a,g]quinoline compound of general formula (I): 
       
         
           
           
               
               
           
         
         an enantiomer, diastereoisomer, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof, 
         wherein R 2  is a hydroxy, a hydroxy-substituted C1-C6 alkyl, a substituted or unsubstituted C1-C6 alkoxy, a halogen, a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C2-C6 alkynyl, a substituted or unsubstituted C3-C6 cycloalkyl, a substituted or unsubstituted C1-C6 alkanoyl, a substituted or unsubstituted C6-C20 aryl, a substituted or unsubstituted benzyl, an amino acid or N-protected amino acid, or —(CO) R 9 ; 
         when R 2  is a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C1-C6 alkoxy, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C2-C6 alkynyl, or a substituted or unsubstituted C3-C6 cycloalkyl, a substituent for substitution can be a halogen or COOR 10 ; 
         when R 2  is a substituted or unsubstituted C1-C6 alkanoyl, a substituted or unsubstituted C6-C20 aryl, or a substituted or unsubstituted benzyl, a substituent for substitution is selected from the following group: C1-C6 alkyl, a halogen, C1-C6 alkoxy; 
         wherein R 9  is a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C2-C6 alkynyl, a substituted or unsubstituted C6-C20 aryl, or heteroaryl selected from thiazolyl, pyrazolyl, imidazolyl, thienyl, furyl, pyrrolyl, or pyridyl; 
         when R 9  is a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, or a substituted or unsubstituted C2-C6 alkynyl, a substituent for substitution is a carboxyl, a substituted or unsubstituted C6-C20 aryl, or heteroaryl selected from thiazolyl, pyrazolyl, imidazolyl, thienyl, furyl, pyrrolyl, or pyridy; 
         when R 9  is a substituted or unsubstituted C6-C20 aryl, a substituent for substitution is a C1-C6 alkyl, a halogen or a C1-C6 alkoxy; R 10  is H, a C6-C20 alkyl substituted or unsubstituted C1-C6 alkyl, a C2-C6 alkenyl, or a C2-C6 alkynyl; when R 2  is an amino acid or N-protected amino acid, the amino acid can be D-amino acid, L-amino acid or racemate; 
         each of R 3 , R 4  is independently H, a halogen substituted or unsubstituted C1-C6 alkyl, a halogen substituted or unsubstituted C1-C6 alkoxy, a C2-C6 alkenyl, a C2-C6 alkynyl, a halogen, COOR 11 , or CONR 12 R 13 , wherein R 11  is H, a substituted or unsubstituted C1-C6 alkyl, a C2-C6 alkenyl, a C2-C6 alkynyl, a substituted or unsubstituted C6-C20 aryl, or a substituted or unsubstituted benzyl; when R 11  is a substituted or unsubstituted C6-C20 aryl, or a substituted or unsubstituted benzyl, a substituent for substitution is a C1-C6 alkyl, a halogen or a C1-C6 alkoxy; when R 11  is a substituted or unsubstituted C1-C6 alkyl, a substituent for substitution is a halogen; each of R 13 , R 12  is independently H, a substituted or unsubstituted C1-C6 alkyl or they and nitrogen atom together form azetidine, pyrrolidinyl, piperazinyl, or morpholinyl, when R 13  or R 12  is a substituted or unsubstituted C1-C6 alkyl, a substituent for substitution is a halogen; 
         each of R 1 , R 5 , R 6 , R 7 , R 8  is independently H, a hydroxy, a hydroxy-substituted C1-C6 alkyl, a halogen-substituted or unsubstituted C1-C6 alkyl, a halogen substituted or unsubstituted C1-C6 alkoxy, a halogen, a C3-C6 cycloalkyl, a halogen substituted or unsubstituted C2-C6 alkenyloxy, a halogen-substituted or unsubstituted C3-C6 alkynyloxy, a substituted or unsubstituted benzyloxy, a substituted or unsubstituted C6-C20 aryl, R 14 COO—, R 15 R 16 N—; when R 1 , R 5 , R 6 , R 7 , or R 8  is a substituted or unsubstituted benzyloxy, or a substituted or unsubstituted C6-C20 aryl, a substituent for substitution is a C1-C6 alkyl, a halogen, or a C1-C6 alkoxy; wherein R 14  is H, a halogen-substituted or unsubstituted C1-C6 alkyl; each of R 15  and R 16  is independently selected from H, a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, or a substituted or unsubstituted C2-C6 alkynyl or they and nitrogen atom together form azetidine, pyrrolidinyl, piperazinyl, or morpholinyl, when R 15  or R 16  is a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C2-C6 alkynyl, a substituent for substitution is a C1-C6 alkyl, a halogen or a C1-C6 alkoxy; 
         R 1  and R 2  can together form a substituted or unsubstituted 5-7 membered heterocycle, a substituent for substitution is a halogen, or a halogen-substituted or unsubstituted C1-C6 alkyl, C2-C6 alkenyl, or C2-C6 alkynyl; and the heterocycle contains 1-3 heteroatom(s) selected from N, O or S; 
         any two adjacent substituents of R 5 , R 6 , R 7  and R 8  can together form a substituted or unsubstituted 5-7 membered heterocycle, a substituent for substitution is a halogen, or a halogen-substituted or unsubstituted C1-C6 alkyl, C2-C6 alkenyl, or C2-C6 alkynyl; and the heterocycle contains 1-3 heteroatom(s) selected from N, O or S; and 
         the configuration of chiral carbon atom in the compound of general formula (I) is R or S configuration. 
       
     
     
         18 . A pharmaceutical composition comprising a therapeutically effective amount of the substantially optically pure hexahydrodibenzo[a,g]quinoline compound, the enantiomer, diastereoisomer, pharmaceutically acceptable organic salt or inorganic salt, crystalline hydrate or solvate thereof, or mixture thereof according to  claim 17 , and one or more pharmaceutically acceptable carriers. 
     
     
         19 . A method of treating a nervous system disease relating to dopamine receptors and serotonin receptors in a subject in need thereof, comprising administering to the subject the pharmaceutical composition according to  claim 18 . 
     
     
         20 . The method according to  claim 19 , wherein the nervous system disease is Parkinson's disease, schizophrenia, drug addiction, or migraine.