Piperidine Compounds Useful to Treat Cerebrovascular Diseases

The present invention relates to a novel cyclic amine derivative which exhibits an excellent activity as a pharmaceutical.

Various attempts have been made to treat cerebrovascular diseases with a drug. For example, cerebrovasodilators and cerebral metabolism activators are used. So far, however, there has been no drug which is very useful for the treatment of the cerebrovascular diseases. In particular, with respect to cerebrovascular dementia, mental dysfunction, etc. among various symptoms accompanying cerebrovascular diseases, no effective drug has yet been developed.

However, in recent years, a theory that an excitatory amino acid liberated after ischemia seriously participates in the death of nerve cells has attracted worldwide attention. This theory was substantiated by the facts that ischemia brings about liberation of a glutamate and the cell injury derived from ischemia is antagonized by a glutamate antagonist.

The present inventors have paid their attention to the neurotoxic activity of the above-described glutamate in starting the search for a new agent for treating cerebrovascular diseases, particularly an agent for improving a mental symptom accompanying the cerebrovascular diseases and have repeated studies on various compounds for a long period of time. As a result, we have found that a cyclic amine derivative which will be described hereinbelow exhibits an excellent activity on the suppression of glutamate liberation, which have led to the completion of the present invention.

Accordingly, an object of the present invention is to provide a cyclic amine derivative or pharmacologically acceptable salts thereof effective as an agent for improving mental symptoms accompanying cerebrovascular diseases, such as cerebral apoplexy, cerebral hemorrhage, cerebral infarction and cerebral arteriosclerosis, and polyinfarctive dementia, and a process for preparing said compound and pharmacologically acceptable salts thereof. Another object of the present invention is to provide a pharmaceutical comprising as an effective ingredient said compound or pharmacologically acceptable salts thereof.

The object compound of the present invention is a cyclic amine and pharmacologically acceptable salts thereof represented by the following formula (1): ##STR2## wherein A is a naphthyl group or a naphthyl group substituted with a lower alkoxy or hydroxy; phenyl group or a phenyl group substituted with a lower alkyl group or a halogen; a quinolyl group; or a lower alkyl group,

n is an integer of 2 or 3,

X is a group represented by the formula ##STR3## a group of the formula ##STR4## a group represented by the formula ##STR5## or a group represented by the formula ##STR6## and

B is a lower alkyl group; a phenyl group which may be substituted with 1 to 3 of the same or different substituents selected from the group consisting of a halogen, a lower alkyl group, and a lower alkoxy group; or a group represented by the formula --Y--Z wherein Y is a group represented by the formula --O--, a group represented by the formula ##STR7## or a group represented by the formula --NH-- and

Z is a phenyl group which may be substituted with one or two same or different substituents selected from the group consisting of a halogen, a lower alkyl group, and a lower alkoxy group; a naphthyl group; a pyridyl group; a lower alkyl group; or a cycloalkyl group.

The term "lower alkyl group" used in the above definition of A, B, and Z with respect to the compound (I) of the present invention is intended to mean a straight-chain or branched alkyl group having 1 to 6 carbon atoms, and examples thereof include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert- butyl, pentyl (amyl), isopentyl, neopentyl, tert-pentyl, 1-methylbutyl, 2-methylbutyl, 1,2-dimethylpropyl, hexyl, isohexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 2,2-dimethylbutyl, 1,3-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethyl butyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, and 1-ethyl-2-methylpropyl groups. Among them, methyl, ethyl, propyl, isopropyl groups etc. are preferable. A methyl group is most preferable.

n is intended to mean an integer of 2 or 3. When n is 2, the compound is a piperidine derivative. When n is 3, the compound is homopiperidine derivative.

The term "lower alkoxy group" used in the definition of A, B, and Z is intended to mean an alkoxy group derived from the above-described lower alkyl group, and preferable examples thereof include methoxy, ethoxy, propoxy, isopropoxy, butoxy, and isobutoxy groups. Among them, a methoxy group is most preferable.

Examples of the halogen atom involved in the definition of A, B, and Z include chlorine, bromine, fluorine, and iodine.

The term "pharmacologically acceptable salt" is intended to mean a commonly used nontoxic salt, and examples thereof include those of inorganic acids, such as hydrochloride, hydrobromide, sulfate and phosphate, those of organic acids, such as acetate, maleate, tartrate, methanesulfonate, benzenesulfonate, and toluenesulfonate, and salts with amino acids such as arginine and aspartic acid.

In preferably embodiments of the cyclic amine and pharmacologically acceptable salts thereof as defined above, (1) B is a lower alkyl; (2) B is --Y--Z in which Y is --O--; (3) A is a naphthyl group or a naphthyl group having a substituent of a lower alkyl or hydroxy, X is --CO--CH2--, n is 2 and B is --Y--Z in which Y is --O--, --CO-- or --NH-- and Z is phenyl or phenyl having one to three substituents, either the same as or different from each other, selected from the group consisting of a halogen, a lower alkyl, and a lower alkoxyl; or naphthyl: or (4) n is 2, B is a lower alkyl or --YZ and Z is defined as above however to exclude cycloalkyl.

The invention provides a process for preparing a cyclic amine or a pharmacologically acceptable salt thereof as defined above, which comprises the step of reacting a halide compound having the formula: A--X--Hal in which Hal is a halogen and A and X each are defined above, with a compound having the formula: ##STR8## in which n and B each are defined above.

The invention also provides a pharmacological composition which comprises a pharmacologically effective amount of a cyclic amine or a pharmacologically acceptable salt thereof as defined above and a pharmacologically acceptable carrier and then a method for improving, treating or preventing a mental symptom associated with a cerebrovascular disease, which comprises administering a pharmacologically effective amount of a cyclic amine or a pharmacologically acceptable salt thereof as defined above to a subject suffering from the mental symptom associated with a cerebrovascular disease.

The compounds of the present invention may be prepared by various processes. A representative process for preparing the compounds of the present invention will now be described.

Specifically, a halide represented by the general formula (II) is reacted with a compound represented by the general formula (III) to prepare a compound (I) which is an object compound of the present invention.

This reaction is a dehydrohalogenation conducted by any ordinary method while heating in the absence of any solvent or in an organic solvent which does not participate in the reaction, i.e., one selected from among alcoholic solvents, such as methanol, ethanol, and butanol, benzene, toluene, xylene, tetrahydrofuran, chloroform, carbon tetrachloride, and dimethylformamide. In this case, favorable results can be attained by conducting the reaction in the presence of an inorganic salt, such as sodium hydrogencarbonate, potassium carbonate, sodium carbonate or caustic soda, or an organic base such as triethylamine, pyridine, pyrimidine or diethylaniline.

The effect of the present invention will now be described in more detail with reference to the following pharmacological experiment.

A male SD rat was decapitated, and cerebral cortices on both sides were then extirpated to prepare a slice having a thickness of 750 .mu.m (weight: 10 to 20 mg) with a McIlwain tissue chopper. The slice was incubated in a Krebs-Henseleit liquid containing a test compound in the form of a solution thereof for 30 minutes. Then the slice was incubated in one ml of a Krebs-Henseleit liquid containing 50 mM of KC1 and the test compound solution for 60 mins. For control, a solvent was added to a Krebs-Henseleit liquid containing only 50 mM of KC1.

The glutamate liberated in the solution was determined by HPLC, and the glutamate liberation inhibitory activity (%) in 10.sup.-4 M of each test compound solution was calculated by the following equation: ##EQU1##

It is apparent from the above-described pharmacological experiment that the compounds of the present invention have a remarkable glutamate liberation inhibitory activity and exhibit a cell injury protective action and a learning disturbance improving action after ischemia based on this activity. Therefore, the compounds of the present invention exhibit a useful pharmacological action, particularly a remarkable ischemic cerebrovascular disease improving action for the central nervous system and are useful as an agent for improving, treating or preventing mental symptoms associated with cerebrovascular diseases such as cerebral apoplexy, cerebral hemorrhage, cerebral infraction, cerebral arteriosclerosis, and various types of dementia such as polyinfarcted dementia.

Further, the compounds of the present invention exhibited high safety in toxicity tests on rats. Therefore, the present invention is valuable from this viewpoint as well.

When the compounds of the present invention are used as a pharmaceutical for the above-described diseases, they may be orally or parenterally administered. The dose will vary depending on the severity of symptoms, age, sex, weight and sensitivity of patients; method of administration; time and intervals of administration and properties, formulation, and kind of pharmaceutical preparations; kind of effective ingredients, etc., so that there is no particular limitation with respect to the dose. Normally, the compounds may be administered in a dose of about 0.1 to 300 mg, preferably about 1 to 100 mg, per day per adult, ordinarily in one to four portions.

The compounds of the present invention are converted into pharmaceutical preparations in the dosage form of, e.g., injections, suppositories, sublingual tablets, and capsules according to any method which is commonly accepted in the art.

In preparing injections, the effective ingredient is blended, if necessary, with a pH modifier, a buffer, a suspending agent, a solubilizing agent, a stabilizer, a tonicity agent, a preservative, etc., followed by preparation of an intravenous, subcutaneous, or intramuscular injection according to an ordinary method. In this case, if necessary, it is possible to lyophilize these preparations according to any ordinary method.

Examples of the suspending agent include methylcellulose, Polysorbate 80, hydroxyethylcellulose, gum arabic, powdered tragacanth, sodium carboxymethylcellulose, and polyoxyethylene sorbitan monolaurate.

Examples of the solubilizing agent include polyoxyethylene hydrogenated castor oil, Polysorbate 80, nicotinamide, polyoxyethylene sorbitan monolaurate, Macrogol, and ethyl esters of castor oil fatty acids.

Examples of the stabilizer include sodium sulfite, sodium metasulfite, and ether, and examples of the preservative include methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, sorbic acid, phenol, cresol, and chlorocresol.

Representative examples of the present invention will now be described for the purpose of aiding the understanding of the present invention. It is needless to say that the present invention will not be limited to these examples only.

2.5 g of 2-bromo-2'-acetonaphthone, 1 g of methylpiperdine, 0.1 g of potassium iodide, and 3.1 g of triethylamine were added to 100 ml of ethanol. The mixture was refluxed for 20 min. The solvent was distilled off, and dichloromethane was added to the residue. The mixture was washed with water and dried. The dichloromethane was distilled off, and the residue was purified by column chromatography (silica gel) to prepare an oleaginous and oily intended compound. The compound was converted into a hydrochloride by an oridinary method and then recrystallized to prepare 1.87 g of an intended hydrochloride.

melting point: 202.degree.-203.5.degree. C.

elementary analysis: C.sub.18 H.sub.21 NO.HCl

1.5 g of 2-bromo-1'-methoxy-2'-acetonaphthone, 1.3 g of 4-(p-fluorobenzoyl)piperidine hydrochloride, and 1.6 g of triethylamine were added to 60 ml of ethanol. The mixture was refluxed for 15 min. The solvent was distilled off, and dichloromethane was added to the residue. The mixture was washed with water and dried. The dichloromethane was distilled off, and the residue was purified by column chromatography (silica gel) to prepare an oleaginous intended compound. The compound was converted into a hydrochloride by an ordinary method and then recrystallized to prepare 1.38 g of an intended hydrochloride.

melting point: 195.5.degree.-196.2.degree. C.

elementary analysis: C.sub.25 H.sub.24 NO.sub.3 F.HCl

3.8 g of 2-naphthoyl chloride, 5.5 g of 4-(p-fluorobenzoyl)piperidine hydrochloride, and 5 g of triethylamine were added to 100 ml of tetrahydrofuran. The mixture was stirred at room temperature for 1 hr. The solvent was filtered off and then distilled off. Dichloromethane was added to the residue. The mixture was washed with water and dried. The dichloromethane was distilled off, and the residue was purified by column chromatography (silica gel) to prepare a crystal. The crystal was recrystallized to prepare 5 of an intended crystal.

melting point: 130.2.degree.-130.7.degree. C.

elementary analysis: C.sub.23 H.sub.20 NO.sub.2 F

0.63 g of 2-bromo-2'-acetonaphthone, 0.65 g of 4-(m-nitrophenoxy)piperidine hydrochloride, and 1 g of triethylamine were added to 100 ml of ethanol. The mixture was refluxed for 30 min. The solvent was distilled off, and dichloromethane was added to the residue. The mixture was washed with water and dried. The dichloromethane was distilled off, and the residue was purified by column chromatography (silica gel) to prepare an oleaginous intended compound. The compound was converted into a hydrochloride by an ordinary method and then recrystallized to prepare 0.15 g of an intended hydrochloride.

melting point: 214.degree.-215.degree. C.

elementary analysis: C.sub.23 H.sub.22 O.sub.4.HCl

Various compounds shown in Table 2 were synthesized in the same manner as that of Examples 1 to 4.