COMPOUNDS HAVING PERIPHERAL CALCIUM ANTAGONIST, ANTICONVULSIVE AND EUMETABOLIC ACTIVITY, PROCESSES FOR THE PREPARATION THEREOF AND PHARMACEUTICAL COMPOSITIONS CONTAINING THEM

Abstract: 1-(4,4′-Difluorobenzhydryl)-4(-3,4-dimethoxycinna­ myl)piperazine, processes for the preparation thereof by react­ ing a reactive derivative of 3,4-dimethoxycinnamic acid with 1-(4,4′-difluorobenzhydryl)-piperazine and subsequently re­ ducing the carbo-amido bond formed, or by directly conden­ sing cinnamyl halide on 1-benzhydrylpiperazine.

Description: Compounds having peripheral calcium antagonist, anticonvulsive and eumetabolic activity, processes for the preparation thereof and pharmaceutical compositions containing them The present invention relates to 1-(4,4'-difluoro-benzhydryl)-4-(3,4-dimethoxycinnamyl)-piperazine of formula I EMI1.1 and pharmaceutically acceptable acid addition salts thereof. Compound I exhibits potent peripheral calcium an tagonist, anticonvulsive and eumetabolic activities, together with a very low toxicity, and therefore it may be employed in the treatment of circulatory diseases, convulsions and cerebral circulatory diseases. According to the present invention, compound I may be used in therapy in form of the free base as well as in form of pharmaceutically acceptable salts thereof with inorganic or organic acids. Among the salts, particularly preferred is the dihydrochloride which will be hereinafter called, for sake of shortness, also with the abbreviation PU 122. The present invention also relates to pharmaceutical compositions containing as the active ingredient the compounds of the invention, optionally in admixture with suitable conventional excipients. Said pharmaceutical compositions may be administered orally, parenterally or rectally,using conventionally employed carriers, excipients, lubricants, emulsifiers, flavouring and colouring agents, etc. Compound I may be prepared by reacting 1-(4,4'difluoro-benzhydryl)piperazine with a reactive derivative of 3,4-dimethoxycinnamic acid, such as its acyl halide, symmetric (homogenous) or mixed anhydri de; and subsequently treating the resulting amide with a suitable reducing agent. Alternatively, compound I may be prepared by condensing l-(4,4'-difluoro-benzhydryl)piperazine on the cinnamoyl halide in the presence of an organic or inorganic base. The following examples furtherillustratethe inven tion, without limiting in any way the scope thereof. EXAMPLE 1 a) 3,4-Dimethoxycinnamoyl chloride 3,4-Dimethoxycinnamic acid (9.85 g; 0.05 mole) was reacted with thionyl chloride (50 ml). The reaction mixture was boiled under stirring for 5 hours, then the excess thionyl chloride was evaporated under reduced pressure and a dark residue was obtained which was taken up in anhydrous benzene (50 ml) and evaporated under reduced pressure. Such a treatment was repeated one more time, and the resulting resi due was employed in the subsequent step, optional ly after crystallization from ligroine (7.0 g; 0.031 mole; 61.7% yield). M.p. 82-830C (not correct ed). b) l-(4,4'-Difluorobenzhydryl)-4-(3,4-dimethoxycin- namoyl)piperazine l-(4,4'-Difluorobenzhydryl)piperazine (7.1 g; 0.0247 mole) was dissolved in anhydrous toluene (75 ml); then anhydrous triethylamine (2.5 g; 3.5 ml; 0.0247 mole) was added and the reaction mixture was cooled to about 5"C, thereafter the previously prepared acyl chloride (5.6 g; 0.0247 mole) diluted in anhydrous toluene (30 ml) was added, under slow stirring. After completion of the addition, the temperature was left raise to the room temperature, then the reaction mixture was gradually heated to reflux, which was kept for about 4 hours. The course of the reaction, during which triethylamine hydrochloride and part of the desired amide separated, was checked by TLC. After cooling, the reaction mixture was evaporated and the residue was treated with water (200 ml). The resulting aqueous emulsion was extracted with dichloromethane (200 ml x 3), the organic layer was washed in turn with water, 5% aqueous sodium hydroxide, water, then it was dried over Na2S04, decolori zed with active carbon, filtered and evaporated, to obtain the desired amide, which was cristallyzed from ethanol (800 ml) to give the pure product (5.5 g; 0.01 mole; 46.5% yield), melting at 220-2220C (not corrected). Elemental analysis: for C28 28 2N2 3 (p.m. 478.55) Calc.% = C 70.28 H 5.90 N 5.85 Found % = C 70.12 H 5.88 N 5.90 TLC = silica gel plates; eluent absolute EtOH; U.V. light = unitary spot; Rf = 0.78. c) l-(4,4'-Difluorobenzhydryl)-4-(3,4-dimethoxycin- namyl)piperazine dihydrochloride To a suspension of aluminium-lithium hydride (1.3 g) in anhydrous tetrahydrofuran (300 ml) a solution of the amide from step b) (16.5 g; 0.034 mole) in anhydrous tetrahydrofuran (800 ml) was slowly added; after that the reaction mixture was stirred for about 8 hours, then it was treated in turn with ethyl ace tate, water, 20% aqueous sodium hydroxide, and water. The alkali hydrates were filtered off and the filtrate was evaporated under reduced pressure, to give an oily residue which was dissolved in dichlorometane. The resulting solution was washed in turn with water, 5% aqueous sodium hydroxide and water; dried on K2S04, filtered and evaporated to give an oily residue (17 g; 0.036 mole) which was salified in an ethanol-ether mixture by addition of hydrochloric acid dissolved in ethanol. The precipitated raw salt was crystallized from ethanol (300 ml) to chromathographic purity (5.0 g; 0.0093 mole; 27.5% yield). Elemental analysis for 32 H Cl F N 0 (p.m.537.49) L28n3 Calc.% = C 62.57 H 6.00 N 5.21 Found % = C 62.52 H 6.13 N 5.17 M.p. = 231-2330C (not corr.) TLC = silica gel plates-eluent absolute EtOH U.V. light - unitary spot Rf = 0.65. EXAMPLE 2 a) l-(4,4'-Difluorobenzhydryl)-4-(3,4-dimethoxycin- namoyl)piperazine 3,4-Dimethoxycinnamic acid (9.85 g; 0.05 mole) was dissolved in anhydrous acetone (100 ml), after that anhydrous triethylamine (5.56 g; 7.6 ml; 0.055 mole) was added. The reaction mixture was cooled to 0-50C, than ethyl chlorocarbonate was added. The mix ture was stirred at the same temperature, for about 20 minutes, during which time the triethylamine hydrochloride separated, the mixed anhydride forming in the solution. l-(4,4'-Difluorobenzhydryl)piperazine (14.4 g; 0.05 mole) was separately dissolved in anhydrous acetone (80 ml) and the resulting solution was added in one portion to the flask containing the mixed anhydride. The mixture was stirred for 60 minutes at about 0-5 , then for about 4 hours, allowing the temperature to raise to the room temperature. The reaction was checked by TLC (abs. EtOH). After completion of the reaction, the solution was filtered and the filtrate was evapora ted under reduced pressure, to give a residue which was treated with dichloromethane. The resulting solution was washed in turn with water, 5% aqueous sodium hydroxide, water, 1% aqueous hydrochloric acid and water. The organic solution was dried over K2S04, filtered and evaporated to give the de sired salt (18.9 g; 0.039 mole; 79% yield) which was crystallized from ethanol. The obtained product was the same as the one of example Ib) (m.p.; mixed m.p.; TLC). b) l-(4,4' -Difluorobenzhydryl)-4-(3,4-dimethoxycin- namyl)piperazine dihydrochloride The amide from step a) was reduced and worked out as described in Example Ic) to give the title compound, which was the same as the one obtained according to Example I (m.p.; mixed m.p.; TLC). EXAMPLE 3 1-(4,4'-Difluorobenzhydryl)-4-(3,4-dimethoxycinna- myl)piperazine dihydrochloride l-(4,4'-Difluorobenzhydryl)piperazine (32.3 g; 0.112 mole), 3,4-dimethoxycinnamoyl chloride (28.82 g; 0.112 mole) and potassium carbonate (15.5 g; 0.112 mole) were mixed in l-butanol (100 ml); the reaction mixture was boiled to reflux for 9 hours. The course of the reaction was checked by TLC (abs. EtOH). After cooling, the inorganic salts were filtered off and washed on the filter with l-butane; then filtrate and washings collected were evaporated to dryness under reduced pressure. The resulting oily residue was treated with dichloromethane, and the organic solution was washed in turn with water, 5% aqueous sodium hydroxide and water, dried over K2C03, filtered and evaporated under reduced pressure, to give an oily residue (19.2 g; 0.041 mo le; 36.9% yield) which was salified and crystallized, as described in Example lc). The bishydrochlo ric salt obtained was the same as in the above exam ples (m.p.; mixed m.p.; TLC). EXAMPLE 4 1-(4,4'-Difluorobenzhydryl)-4-(3,4-dimethoxycinna- myl)piperazine dihydrochloride 1-(4,4'-Difluorobenzhydryl)-4-(3,4-dimethoxycin- namoyl)piperazine (2.87 g; 0.006 mole) obtained as described in Example lb) was dissolved in tetrahydrofuran (20 ml) and the solution was treated with sodium borohydride (1.2 g; 0.031 mole). The reaction mixture was cooled to about 100C, then trifluo roacetic acid (2.3 ml; 0.031 mole) diluted with tetrahydrofuran (10 ml) was added dropwise during a hour. The mixture was refluxed for 48 hours under stirring, then,after cooling, the excess reactive was destroyed by acidification with 10% aqueous hydrochloric acid. The reaction mixture was filtered and the filtrate was evaporated under reduced pressure. The resulting residue was crystallized to purity from ethanol, obtaining the title compound (0.6 g; 19% yield) which was the same as the one obtained in Example lc). Compound PU 122 proved to have a vasodilating ac tivity higher than that of Flunarizine, a well known vasodilative agent, used as a comparison. Moreover, PU 122 shows an interesting calcium antagonist activity, and a platelet antiaggregating activity higher than that of the acetylsalicylic acid. Cerebral perfusion in the rabbit The cerebral vasodilative activity of PU 122 in comparison with Flunarizine was tested by the method of the cerebral perfusion in the rabbit according to the procedure of Von P. Vaupel e H. Hutten (1980), by measurement of the decrease of the peripheral resistances in the cerebral district. Said changement was determined by means of a transducer, by measuring the hematic pressure at the cerebral level and scoring the lasting of action of the compound under test. The two test compounds were administered by intraarterial route at the dosage of 0.9 pM, in a volume of 0.2 ml for each animal. The results are reported in the following Table 1, which shows how PU 122 has a marked vasodilative activity at the cerebral level, substantially higher than that of Flunarizine. TABLE 1 - Cerebral vasodilative activity in the rabbit of PU 122 and Flunarizine. Perfu sion of the cerebral district. EMI8.1 <tb> Treatrtent <SEP> Doses <SEP> NO <SEP> of <SEP> Difference <SEP> Lasting <SEP> Area <tb> <SEP> uM <SEP> ani- <SEP> in <SEP> A <SEP> of <SEP> the <SEP> 2 <tb> <SEP> i.a. <SEP> mals <SEP> pressure <SEP> effect <tb> <SEP> (min.) <tb> <SEP> 1 <tb> Flunarizi <SEP> 0.9 <SEP> 5 <SEP> 10.25 <SEP> 25.12 <SEP> 12.50 <SEP> 314.2 <tb> ne <tb> PU <SEP> 122 <SEP> 0.9 <SEP> 5 <SEP> 18.75 <SEP> 29.17 <SEP> 16.70 <SEP> 487.14 <tb> Rat hind quarters The vasodilative activity of PU 122 in comparison with Flunarizine was further evaluated according to the procedure described by F.N. Fastier and F.H. Smirk, (J. Pharm. Exp. Therap. 89, 256-270; 1974), by measuring the antagonist action of the test compound against hyperkaliemia induced vasoconstriction. The compounds under test were used at 5.10 5 M concentration. The results are reported in the following Table 2, which shows how both the test compounds have high vasodilative activity, PU 122 being markedly more active. TABLE 2 - Vasodilative activity of PU 122 and Flu narizine. Rat hind quarters perfused wi th hyperkaliemic tyrode. EMI9.1 <tb> treatment <SEP> Concentra- <SEP> NO <SEP> of <SEP> Perfusion <SEP> pressure <tb> <SEP> tion <SEP> ani- <SEP> basal <SEP> ter <SEP> 10' <SEP> A <SEP> A% <tb> <SEP> mals <tb> <SEP> -5 <tb> PU <SEP> 122 <SEP> 5 <SEP> x <SEP> 10 <SEP> M <SEP> 5 <SEP> 195.00 <SEP> 90.00 <SEP> 105.00 <SEP> 53.8 <tb> Flunari <SEP> 5 <SEP> x <SEP> 10 <SEP> M <SEP> 5 <SEP> 175.00 <SEP> 95.00 <SEP> 80.00 <SEP> 45.7 <tb> zine <tb> Ca ++ antagonist activity ++ The Ca antagonist activity of PU 122 in comparison with Nifedipine was evaluated by measurement ++ of the 45 Ca uptake, according to the procedure of Deana et al. (Biochem. J., 218, 899-905, 1984), in synaptosomial preparations of rat brain, obtained according to the method of Booth and Clark (Bio chem. J. 176, 365-370, 1978). The results are reported in Table 3, which shows how PU 122 has a remarka ++ ble inhibitory effect on the Ca uptake in rat brain synaptosomes, even though lower than that of Nifedipine as a standard control. ++ TABLE 3 - Ca antagonist activity EMI10.1 <tb> PU <SEP> 122 <SEP> -16.48 <SEP> <tb> Nifedipine <SEP> -50% <tb> Platelet antiaggregating activity The inhibitory effect on platelet aggregation induced BY ADP on human platelet rich plasma (PRP) was evaluated for PU 122 in comparison with acetylsalicy lic acid, according to the procedure described by G.V.R. Born (Nature, 194, 927; 1962). The obtained results proved how PU 122 has a strong platelet antiaggregating activity with a IC50 substan tially better than that of acetylsalicylic acid used as the reference drug. The present invention refers also to all the industrially applicable aspects connected with the therapeutic use of compound I or of its salts. An essential aspect of the invention is therefore provided by phar maceutical compositions containing, as active principle, predetermined and therapeutically effective amounts of compound I or of its salts, in addition with carriers conventionally used in pharmaceutical preparations. Examples of such pharmaceutical formulations comprise tablets, sugar coated tablets, syrups, suppo sitories, vials for intramuscolar or intravenous injection, containing from 1 to 250 mg of active principle and can be administered 1 or more times a day according to the diagnosis and weight and age of the patient.

Claims: CLAIMS for the Contracting States: BE, CH, DE, FR, GB, IT, LI, LU, NL, SE 1. l-(4,4'-Difluorobenzhydryl)-4-(3,4-dimethoxy- cinnamyl)piperazine of general formula EMI12.1 and its pharmaceutically acceptable salts with organic or inorganic acids. 2. As a compound according to claim 1, 1-(4,4'difluorobenzhydryl)-4-(3,4-dimethoxycinnamyl)pipera zine dihydrochloride. 3. A process for the preparation of compounds according to claims 1-2, characterized by reacting a reactive derivative of 3,4-dimethoxycinnamic acid with l-(4,4'-difluorobenzhydryl)piperazine and subsequently reducing the resulting compound by means of reducing agents such as metallic hydrides. 4. Pharmaceutical compositions having peripheral calcium antagonist, anticonvulsive and cerebral eu metabolic activity, containing as the active principle the compounds according to claims 1-2. 5. Pharmaceutical compositions according to claim 5, in form of capsules, tablets, dragees, syrups, solutions, granulates, lozenges, vials. CLAIMS for AT 1. Process for the preparation of 1-(4,4'-difluo robenzhydryl)-4-( 3, 4-dimethoxycinnamyl)piperazine of aeneral formula; EMI13.1 characterized by reacting a reactive derivative of 3,4-dimethoxycinnamic acid with l-( 4,4' -difluoro- benzhydryl)piperazine and subsequently reducing the resulting compound by means of reducing agents. 2. Process according to claim 1 characterized in that the reaction is carried out in the presence of a tertiary organic base. 3. Process according to claim 1 wherein the reduc tion is carried out by means of metal hydrides such as lithium aluminium hydride or sodium borohydride. 4. Process for the preparation of 1-(4,4'-difluorobenzhydryl)-4-(3,4-dimethoxycinnamyl)piperazine characterized by reacting a 3,4-dimethoxycinnamyl halide with l-(4,4'-difluorobenzhydryl)piperazine in the presence of a tertiary organic base.

Inventors: QUADRO, GIUSEPPE
Applicants: PULITZER ITALIANA S.P.A.
Application year: 1985
Main classification: C07D295
IPC codes: C07D295