2-OXOPYRROLIDINE PHARMACEUTICAL COMPOUNDS, SALTS THEREOF, AND THE PREPARATION THEREOF

Abstract: 2-oxopyrroldine compounds are represented by the for­ mula wherein R and R are hydrogen, alkyl or cycloalklyl, A is an alkylene or phenyl-substituted alkylene group, and B is an alkylene group, Synthesis is by condensation of the reactants having groups -COOR + HR² N- where R is alkyl, with equimolar amounts of reactants, with or without solvent at 80 - 150°C. An acid addition salt may then be formed. Pharmaceutical compositions in solid or liquid form con­ tain the compound or salt, for oral or injectable use in amount of 1-1000 mg/day, to prevent or cure cerebral dysfunction.

Description: The present invention relates to novel 2-oxopyrrolidine compounds, salts therof, a process for the preparation of the compounds or salts, as well as a pharmaceutical agent comprising at least one such compound or salt and useful to prevent or cure cerebral dysfunction. Hitherto, various studies have been made on γ₋ amino butyric acid (GABA) and its derivatives to seek an effective component for curing cerebral dysfunction. During these studies, 2-oxo-1-pyrrolidineacetamide (Piracetam, 2-(pyrrolidin-2-on-1-yl) acetamide) has been discovered and has been expected to be useful, but its pharmaceutical effects have been found to be inadequate. A primary object of the invention is to provide an effective agent for preventing or curing cerebral dysfunction, which can be substituted for the Piracetam. A secondary object of the invention is to provide an agent for preventing or curing cerebral dysfunction, which has a strong pharmaceutical action and no or quite low toxicity. According to the invention, a novel 2-oxopyrrolidine compound is represented by the general formula: wherein R¹ and R² are each a hydrogen atom or a straight-chain alkyl group having 1 to 10 carbon atoms, an isopropyl, iso-butyl, s -butyl, tert -butyl or isopentyl group or a cycloalkyl group having 3 to 6 carbon atoms, A is a straight-chain alkylene group having 1 to 3 carbon atoms or a branched-chain alkylene group having 2 to 10 carbon atoms which alkylene groups may be phenyl-substituted; and B is a straight-chain alkylene group having 1 to 3 carbon atoms or a branched-chain alkylene group having 2 to 10 carbon atoms. The invention also includes the pharmaceutically acceptable acid addition salts of these compounds. The compounds (I) and salts thereof have an excellent cerebral metabolic activating action and cerebral function protecting action, and have a quite low toxicity. In the compounds of Formula (I), the alkyl group may be a straight-chain alkyl radical, branched-chain alkyl radical or cycloalkyl radical. Examples for the straight-chain alkyl radicals, having 1 to 10 carbon atoms, are methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl and n-decyl. Examples of the branched-chain alkyl radicals are isopropyl, isobutyl, s -butyl, t -butyl and isopentyl. Examples of the cycloalkyl radicals are cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. The alkylene group may be straight-chain or branched chain. Examples of straight-chain alkylene radicals, having 1 to 3 carbon atoms, are methylene, ethylene and trimethylene. Examples of branched-chain alkylene radicals, having 2 to 10 carbon atoms, are ethylidene, propylidene, butylidene, pentylidene, hexylidene, decylidene, isopropylidene, isobutylidene, isopentylidene, isobutylidene, isopentylidene, propylene, ethylethylene and ethyltrimethylene. The salts of the compound (I) are acid addition salts having no toxicity. Suitable acids for forming a salt are hydrogen chloride, hydrogen bromide or the like hydrogen halide, sulfuric acid, phosphoric acid or the like mineral acid, acetic acid, propionic acid, gluconic acid, maleic acid, fumaric acid, tartaric acid, succinic acid, lactic acid, benzoic acid, cinnamic acid or the like organocarboxylic acid, methanesulfonic acid or the like alkylsulfonic acid, p-toluenesulfonic acid or the like arylsulfonic acid, cyclohexyl-sulfonic acid or the like cycloalkysulfonic acid, and asparaginic acid, glutamic acid, N-acetylasparaginic acid, N-acetylglutamic acid or the like amino acid. According to the process of the invention, the compounds (I) and salts thereof can be prepared by reacting a compound represented by the formula wherein R¹ and A have the meanings defined above, and R is an alkyl group, with a compound represented by the formula wherein R² and B are as defined above, and if necessary, converting the resulting compound into the salt. The reaction proceeds merely by stirring both reactants in equimolar amount in the presence or absence of a solvent. As the solvent, toluene, xylene, N,N-dimethylformamide, N, N-dimethylacetamide or the like may be employed. The reaction temperature depends on the kind and other factors of the raw materials and solvent and thus it is not always constant, but 80 to 150 o C is preferable. Each of the reactants can be prepared in a known manner. For instance, the compound of Formula (II) may be synthesized in accordance with the process disclosed in Jap. Unexamined Patent Application Gazette No. 130656/1978, and that of the Formula (III) may be synthesized in accordance with the process disclosed in Jap. Unexamined Patent Application Gazette No. 156283/1981. The invention also includes medicaments (pharmaceutical compositions) comprising a pharmaceutically effective amount of a compound or salt according to the invention. There is no limitation on the form of the medicine and thus it may be a tablet, pill, hard capsule, soft capsule, powder, granule, suppository or the like solid medicament, or solution, suspension, emulsion or the like liquid medicament. In the case of a solid medicament a starch, lactose, glucose, calcium phophate, magnesium stearate, gum arabic or the like forming agent if necessary, smoothening or greasing agent, binding agent, breaking agent, coating agent, coloring agent or the like may be added. In the case of a liquid medicament, a stabilizer, dissolving aid, suspending agent, emulsifying agent, buffering agent, storage improvement agent of the like may be added. The dosage amount of the compound or salt depends on various factors such as the particular compound, nature of the disease, and age and state of the patient, but for an adult, about 1 to 1000 mg/day and more particularly 5 to 30 mg/day is preferable. The present invention has the following advantages. By the process of the invention, the compounds and salts thereof can be prepared easily and with a relatively high yield by starting from raw materials which are known or can easily be synthesized with use of known materials. The compounds and salts thereof according to the invention are excellent in cerebral metabolic activating action and cerebral function protecting action and show a quite low toxicity, so that they are quite useful as effective components for a cerebral dysfunction curing or preventing agent. Therefore, the agent can be orally or non-orally dosed to patients with senile dementia due to a primary cerebral degeneration, cerebral vascular dementia based on a cerebral vascular dysfunction and particularly cereblosclerosis, or a combined type dementia based on both of these factors. The compound or salt may be dosed to a person without learning ability, amnesiac or patient with an impairment of consciousness due to injury to the head, for the purpose of appearance of activating action in the central nervous system, or preventing such diseases. The invention will now be further explained with reference to the following Examples of preparation of the compounds and salts, Pharmacological Test Examples thereof and Examples of making pharmaceutical preparations. Example 1 7a-(2-oxo-1-pyrrolidineacetamidomethyl)pyrrolizidine A mixture consisting of 14.1g (89.6 mmol) of methyl 2-oxo-1-pyrrolidineacetate and 11.4g (81.4 mmol) of 7a-(aminomethyl)pyrrolizidine was heated and stirred for 6 hours at 80°C under argon atmosphere. After cooling, the reaction mixture was then dissolved in a suitable amount of aqueous 1.ON-hydrochloric acid and extracted 3 times with dichloromethane. The aqueous layer was rendered alkaline by the addition of sodium hydroxide solution and extracted 3 times with dichloromethane followed by drying over anhydrous magnesium sulfate. After removal of the drying agent through filtration, the solvent was evaporated under reduced pressure to obtain a yellowish oil as a free base of the desired compound. The free base was converted to the terephthalate by usual manner. Yield : 32.0g (91.1%). Terephthalate Melting point : 193.2 °C Elementary analysis : C₁₄H₂₃N₃O₂·C₈H₆O₄ Cal. : C, 61.24; H, 6.77; N, 9.74 Found : C, 61.19; H, 6.91; N, 9.58 1665, 1535, 1400 Mass spectrum (EI/DI) m/z : 166, 149, 110 (base peak) Free base NMR spectrum (CDCl₃) δ ppm : 1.07 - 3.17 3.17 3.52 3.95 6.43 - 6.93 (1H, br, NH) Examples 2 to 4 Following products were prepared by the procedure described in Example 1. a) 7a-(2-oxo-1-pyrrolidineacetamidoethyl)pyrrolizidine Picrate Yield : 69.3% Melting point : 168 - 9°C Elementary analysis : C₁₅H₂₅N₃O₂·C₆H₃N₃O₇ Cal. : C, 49.60; H, 5.55; N, 16.53 Found : C, 49.51; H, 5.54; N, 16.53 1684, 1655, 1635, 1560, 1319 Mass spectrum (EI/DI) m/z: 279 (M⁺), 110 (base peak) Free base NMR spectrum (CDCl₃) δ ppm : 1.45 - 3.50 3.53 3.95 8.50 - 8.95 (1H, br, NH) b) 7a-[2-(2-oxo-1-pyrrolidine)butylamidomethyl]pyrrolizidine Telephthalate Yield : 69.3% Melting point : 195 - 7°C (dec.) Elementary analysis : C₁₆H₂₇N₃O₂·C₈H₆O₄ Cal. : C, 62.73; H, 7.24; N, 9.14 Found : C, 62.49; H, 7.41; N, 9.18 3262, 2890, 1671, 745 Mass spectrum (EI/DI) m/z: 166, 149, 110 (base peak) Free base NMR spectrum (CDCl₃) δ ppm : 0.90 (3H, t, J = 7.0Hz, -CH₃) 1.40 - 3.20 3.18 3.49 4.35 - 4.70 6.40 - 6.95 (1H, br, NH) c) 7a-[2-(2-oxo-1-pyrrolidinyl)-2-phenylacetamidomethyl]pyrrolizidine Telephthalate Yield : 83.0% Melting point : 227 - 9°C (dec.) Elementary analysis : C₂₀H₂₇N₃O₂·2/3 C₈H₆O₄ Cal. : C, 67.28; H, 6.91; N, 9.29 Found : C, 62.23; H, 7.11; N, 9.33 3228, 1676, 1572, 1381, 1288, 812, 746 Mass spectrum (EI/DI) m/z: 110 (base peak) Free base Melting point : 110 - 2°C NMR spectrum (CDCl₃) δ ppm : 1.30 - 4.05 3.25 5.89 6.20 - 6.65 (1H, br, NH) 7.43 (5H, s, aromatic protons) Example 5 7a-(5-methyl-2-oxo-1-pyrrolidineacetamidomethyl)pyrrolizidine This compound was obtained by use of the conditions described in Example 1 and starting from methyl 5-methyl-2-oxo-1-pyrrolidineacetate instead of methyl 2-oxo-1-pyrrolidineacetate. NMR spectrum (CDCl₃) δ ppm : 1.25 (3H, d, J = 6.0Hz, CH₃) 1.10 - 4.00 3.20 3.95 6.40 - 6.95 (1H, br, NH) Example 6 N-methyl-7a-(2-oxo-1-pyrrolidineacetamidomethyl)pyrrolizidine A mixture consisiting of 1.60g (10.2 mmol) of methyl 2-oxo-1-pyrrolidineacetate and 1.54g (10.0 mmol) of 7a-methylaminomethylpyrrolizidine was heated and stirred for 3 hours at 140 to 150°C under argon atmosphere and then the reaction mixture was treated in the manner as described in Example 1 to obtain the desired compound. Yield : 2.17g (77.8%) 2950, 2860, 1690, 1660, 1465, 1290 Mass spectrum : (EI/DI) m/z ; 110 (base peak) (CI/DI) m/z ; 270 [(M÷1)⁺, base peak] NMR spectrum (CDCl₃) δ ppm : 1.30 - 4.90 3.08 and 3.20 (3H, each s, N-CH₃) 3.55 4.13 and 4.40 Pharmacological Test Example 1 (Effect on cerebral energy metabolism) Cerebral metabolities were measured following bilateral common carotid artery occlusion in rats according to the method of Fujishima et al [ "Rinsho to Kenkyu" (translated as --Clinic and Study--), Vol. 51, page 3532, 1974, Japan. Spontaneously hypertensive male rats (SHR), each of which had a weight of 250 to 350g and a blood pressure above 150 mm Hg, were anesthetized with ether. The common carotid artery was exposed bilaterally and double ligated simultaneously. After 1 hour, a drug to be tested was orally administered and after having lapsed 5 hours from the administration, each of the animals was exposed to microwaves (5.0 KW, 1.5 seconds). The cortex portion of brain was isolated and homogenated. Adenosin-tri-phosphate (ATP), glucose-6-phosphate (G-6-P), glucose, lactate and pyruvate concentrations in the tissue homogenate were determined by standard enzymatic methods. As shown in the following Table 1, it is seen that the test compound (Example 1) improves cerebral energy metabolism in cerebral ischemia. Pharmaceutical Test Example 2 (Effect on gasping number after decapitation) Cerebral protective effects of the compound according to the invention were examined in the complete ischemic model using the number of gaspings of the decapitated head of mice, in accordance with the method of Holowach-Thurston J. et al ( "Pediatr.", Vol. 8, Page 238, 1974). Male ddY mice of 20 to 26g were used. After having lapsed 30 minutes from an oral administration of the test compound, mice were decapitated and the number of gaspings of the isolated heads were counted. As shown in following Table 2, it is seen that the test compound has cerebral protective actions. Pharmaceutical Test Example 3 (Effect on posttraumatic consciousness disturbance) Cerebral protection from posttraumatic consciousness distubance of mice was investigated by using the method of Manaka et al ("Igaku no Ayumi" (translated as --The Course of Medical Science--), Vol. 104, Page 253, 1978, Japan). Male ddY mice having weight of 20 to 26g were used. After a lapse of 30 minutes from oral administration of a test compound, the mice were put into a comatose state by dropping a stick (weight : 36g) on the head from the height of 40cm. The time of appearance of the righting reflex and spontaneous movement from this comatose state were measured. As shown in following Table 3, it is seen that the test compound has significant cerebral protective effects in consciousness disturbance. Pharmaceutical Test Example 4 (Acute toxicity) A test compound was given to male ddY mice having weight of 19 to 23g to observe acute toxicity and weight change. Results are shown in the following Table 4. There was found neither a death nor any inhibition of weight increase. This means that the toxicity of the compound according to the invention is quite low. Dose (mg/kg) Number of mice Weight 1st day 3rd day Control - 10 21.0 ± 0.3 24.4 ± 0.3 Product of Ex. 1 100 10 20.9 ± 0.3 24.6 ± 0.3 1000 10 21.0 ± 0.3 24.4 ± 0.5 Pharmaceutical Agent Preparation Example 1 (Tablet) 120g of the product according to Example 1 were mixed with 1000g of lactose and 48g of hydroxypropylcellulose. The mixture was granulated with use of aqueous solution of ethanol (ethanol : water = 50 : 50), dried and screened. The resulting granules were mixed with 34g of corn starch and punched in a conventional manner to obtain 6000 tablets, each containing 20mg of the compound. If necessary, the tablets can be coated with a film or sugar, in a conventional manner. Pharmacological Agent Preparation Example 2 (Capsules) Component Amount Product of Example 1 200 (g) Lactose 1470 Magnesium stearate 30 The components were mixed. The resulting powder mixture was charged into hard gelatin capsules, so as to contain 170mg of the mixture and to obtain 10000 capsules, each of which contains 20mg of the compound. Pharmaceutical Agent Preparation Example 3 (Granules) Component Amount Product of Example 1 400 (g) Hydroxypropylcellulose 200 Corn starch 3380 Lactose 6000 Magnesium stearate 20 The components were mixed and treated in a conventional manner to obtain 10kg of granules which were packed separately, each containing 0.5g of the granules (each package contains 20mg of the compound). Pharmaceutical Agent Preparation Example 4 (Injectable Solution) A solution was prepared in a conventional manner to the following prescription. Component Amount Product of Example 1 100 mg Polyethylene glycol 2 ml Distilled water remainder (total) 5 ml/vial Pharmaceutical Agent Preparation Example 5 (Injectable Solution) A solution was prepared in a conventional manner to the following prescription. Component Amount Product of Example 1 100 mg Sodium acetate 2 mg Acetic acid (to control pH to 5.8) suitable amount Distilled water remainder (total) 5 ml/vial

Claims: A 2-oxopyrrolidine compound represented by the formula wherein R¹ and R² are each a hydrogen atom or a straight-chain alkyl group having 1 to 10 carbon atoms, an isopropyl, iso-butyl, s -butyl, tert -butyl or isopentyl group or a cycloalkyl group having 3 to 6 carbon atoms, A is a straight-chain alkylene group having 1 to 3 carbon atoms or a branched-chain alkylene group having 2 to 10 carbon atoms which alkylene groups may be phenyl-substituted; and B is a straight-chain alkylene group having 1 to 3 carbon atoms or branched-chain alkylene group having 2 to 10 carbon atoms; or a salt thereof. A compound or salt as claimed in Claim 1, wherein said compound is 7a-(2-oxo-1-pyrrolidineacetamidomethyl)pyrrolizidine. A compound or salt as claimed in Claim 1, wherein said compound is 7a-(2-oxo-1-pyrrolidineacetamidoethyl)pyrrolizidine. A compound or salt as claimed in Claim 1, wherein said compound is 7a-[2-(2-oxo-1-pyrrolidine)butylamidomethyl]pyrrolizidine. A compound or salt as claimed in Claim 1, wherein said compound is 7a-[2-(2-oxo-1-pyrrolidine)-2-phenylacetamidomethyl]pyrrolizidine. A compound or salt as claimed in Claim 1, wherein said compound is 7a-(5-methyl-2-oxo-1-pyrrolidineacetamidomethyl)pyrrolizidine. A compound or salt as claimed in Claim 1, wherein said compound is N-methyl-7a-(2-oxo-1-pyrrolidineacetamidomethyl)pyrrolizidine. A process for the preparation of a 2-oxopyrrolidine compound as claimed in Claim 1, which comprises reacting a compound represented by the formula wherein R¹ and A are as defined in Claim 1, and R is an alkyl group, with a compound represented by the formula wherein R² and B are as defined in Claim 1, and if necessary, converting the resulting compound into a salt. A pharmaceutical composition for preventing or curing a cerebral dysfunction, which comprises as an effective component at least one 2-oxopyrrolidine compound as claimed in any of Claims 1 to 7.

Inventors: HAYASHI, MOTOHIDE, KUMAGAI, YOSHIHIRO, KURONO, MASAYASU, MATSUMOTO, YUKIHARU, MIURA, KENJI, MIYANO, SEIJI, SUMOTO, KUNIHIRO, SUZUKI, TSUNEMASA
Applicants: SANWA KAGAKU KENKYUSHO CO., LTD.
Application year: 1986
Main classification: C07D487
IPC codes: A61K31, A61P25, C07D487, C07D207