GENESERINE DERIVATIVES AS CHOLINESTERASE INHIBITORS

Abstract: Compounds of formula (I), wherein R is as defined in the disclosure, have useful therapeutical properties, particularly for the treatment of neurologic pathologies.

Description: GENESERINE DERIVATIVES AS CHOLINESTERASE INHIBITORS The present invention relates to geneserine deri¬ vatives , a process for the preparation thereof and pharmaceutical compositions containing them. The compounds of the invention have the following general formula I : wherein R is a straight or branched C_-C 2Q alkyl group, a C--C- cycloalkyl group, a phenyl or benzyl group, op- tionally substituted with C,-C. alkyl groups, halogen atoms, C,-C. alkoxy groups. Preferably R is an alkyl group having 4 to 12 car¬ bon atoms, most preferably 6 to 8 carbon atoms. Compound I, in which R is an n-heptyl group, is particularly preferred. The invention also comprises the salts of com¬ pounds I with pharmaceutically acceptable acids, parti¬ cularly hydrochloric, sulfuric, tartaric, succinic, ma- leic, citric, methanesulfonic, fumaric, acetic, lactic, salicylic acids. The compounds of formula I and the pharmaceuti¬ cally acceptable salts thereof have inhibiting activity against cholinesterase and they can usefully be admini- stered to patients suffering from Alzheimer disease or from various other conditions deriving from a neurolo¬ gic deficiency. Alzheimer disease is a form of progressive demen- tia clinically characterized by loss of memory and im¬ pairment of the intellective activities. The importance of the cholinergic system in Al¬ zheimer disease is well known and the loss of the cholinergic function has been found to be related to both the presence of neuropathologic lesions and a se¬ vere loss of the cognitive functions. On the basis of such evidences, one of the most studied therapeutical approaches is the cholino-mime ic one, intended to improve and increase the cholinergic activity. The most promising results were obtained using cholinesterase inhibitors, particularly physostigmine and tacrine. EP-A-0154864 and EP-A-0298202 disclose physostig- mine derivatives characterized by an increased lipophi- lia, due to the presence of long-chain alkyl or aryl residues on the carbamoyl group which is typical of this class of alkaloids. Geneserine, even though it has been known for many years as an anticholinergic agent and used in therapy as a gastrointestinal antispastic, has never been the object of studies in order to verify its capability to restore the cholinergic function at the level of cen¬ tral nervous system. Now it has been found that geneserine derivatives of formula I have pharmacological properties which are particularly interesting and advantageous compared with the prior art compounds. Compounds of formula I can be prepared by oxidi¬ zing compounds of formula II wherein R is as defined above. The oxidation is preferably carried out by means of organic peracids or peroxides, such as m-chloroper- benzoic acid, monoperphthalic acid, peracetic acid, hy¬ drogen peroxide, in inert solvents such as halogenated hydrocarbons, aromatic hydrocarbons, dimethylformamide, dimethylsulfoxide. The preparation of compounds of formula II from physostigmine is known from EP-A-0154864 and EP-A- 0298202, cited above. Alternatively, compounds I can be obtained star¬ ting from geneserine by hydrolysis of the methylamino- carbonyloxy group and subseguent O-acylation with rea¬ gents capable of introducing the desired function -C-NHR, wherein R is as defined above. II 0 Examples of acylating reagents which can conve¬ niently be used for this purpose comprise alkylisocyanates of formula R-NCO, wherein R is as in formula I, or in alternative substituted imidazolureas of formula III which can be prepared from carbonyldiimidazole and ami¬ nes of formula RNH 2 , wherein R is as defined above. Hydrolysis of geneserine can be carried out analo- gously to that of physostigmine, by reaction with alkali alkoxides, whereas the O-acylation with the sub¬ stituted imidazolureas is carried out in a strictly anhydrous medium, in the presence of metal sodium. The resulting compounds I can then be salified with organic or inorganic non-toxic acids, according to the conventional teσhnigues. Compounds I, for the envi¬ saged therapeutical uses, will be formulated according to conventional technigues and excipients, such as those described in Remington's Pharmaceutical Sciences Handbook, Mack Pub. Co., NY. U.S.A., 18 ma Ed.. The ave¬ rage daily dosage will depend, of course, on many fac¬ tors, but generally it will range from 10 to 1000 mg of compounds I or the salts thereof. The following examples further illustrate the in- vention. EXAMPLE 1 a) Eseroline. To a solution of 5 g of eserine (Sigma or Fluka) in degased anhydrous ethanol (600 ml), 0,4 g of sodium are added portionswise. After about half an hour, sol¬ vent is evaporated off under vacuum at 30 β C and the re- suiting oil is treated with a 10% HCl solution and extracted with 3 x 50 ml of CHC1,. The combined organic phases are then washed with NaCl-saturated water until the red coloration in the aqueous phase disappears. After drying over Na 2 SO. and evaporation under vacuum at 25 β C, an oil is obtained, which is recrystallized from 1/2 ethyl ace¬ tate/petroleum ether, to obtain a solid in a 64% yield (2,54 g). TLC: CHC1 3 /CH 3 0H = 4/1 Rf = 0,4 Developer: ϋV, phenol reactive M.p. = 126 β C (lit. 129 β C) The obtained solid is stored as the hydrochloride; the base is treated with an hydrochloric EtOH solution to acid pH and evaporated under vacuum at 35 β C. M.p. = 150-151°C (lit. 154°C) MS and NMR in conformity. b) N-heptyl-imidazole-urea. To a solution of 10 g of carbonyldiimidazole in 600 ml of anhydrous tetrahydrofuran, cooled at +5 β C and under strong stirring, a solution of 7,1 g of heptyla- mine in 40 ml of anhydrous tetrahydrofuran is added. After 45 minutes the solution is evaporated under va- cuum at 30°C and the obtained oil is treated with 2 x 70 ml of hexane, decanted and used directly for the subsequent reaction. TLC: ethyl acetate/hexane = 3/7 Rf = 0,3 Developer: phenol reactive (green spot) MS and NMR in conformity. c) N-heptyleserine. 0,1 g of sodium are added to a solution of the product obtained according to a) (5 g) in 150 ml of de¬ gased anhydrous ethyl ether, under stirring and nitro- gen atmosphere, and the mixture is left to react for 1 hour at room temperature. Then the product obtained in b) (4,5 g) is added to the reaction mixture, during half an hour. After a day at room temperature, the ether solution is washed with 50 ml of water, dried over Na 2 SO. and evaporated under vacuum at 30°C. The product is purified by P.C. (elueπt ethyl acetate: 3 = hexane: 1 = methanol : 1; Rf = 0,35; stationary phase: silica gel, 30-60 urn). An oily product is obtained, in a 53% yield (4,16 g). NMR in conformity. Purity .90% The product is stored as tartrate. MS, H- and C-NMR in conformity. d) N-heptyl-geneserine. To a solution of 0,52 g of the product obtained in c) in 50 ml of degased chloroform, cooled to about 0 β C, 0,7 g of m-chloroperbenzoic acid of 99% purity (by io- dometric titration, after treatment according to Schwarts and Blungers, J. Org. 29, 1976 (1964)) dissolved in 10 ml of chloroform, are dropped into the reaction mixture keeping the temperature from 0 to 5 β C. After that, the reaction is left at room temperature under stirring overnight. When the reaction is over, the chloroform solution is washed with 50 ml of a NaHCO. saturated solution, then with a NaCl saturated solution, dried over Na^SO. and finally evaporated under vacuum at room temperature. The product is purified by preparative TLC, elu- ting with ethyl ether/triethyla ine 40/1. Rf = 0,8. The product is extracted from silica with chloro- form/methanol = 9,5/0,5 and it is obtained evaporating the solution under vacuum at room temperature. A co¬ lourless oil is obtained in a 35% yield (200 mg). TLC: ethyl ether/triethylamine = 40/1 Rf = 0,8 M MSS;; 1H- and C-NMR; field desorption, mike in confor- mity. EXAMPLE 2 N-heptyl-geneserine. A solution of the product obtained in example 1(c) (1,24 g) in 10 ml of acetone is treated with 14,7 ml of 6% hydrogen peroxide and a tip of CaCO,. The reaction mixture is reacted shielded from light at room tempera¬ ture for 55 hours, until the starting product disappe- ars. Then acetone is evaporated off under nitrogen bub¬ bling and the agueous solution is extracted with 3 x 50 ml of ethyl ether. The separated ether solution is washed with 10% NaHCO,, then with a NaCl saturated aqueous solution, dried over a-SO, and evaporated under vacuum at room temperature to give a colourless oil which is the same as the product described in example 1(d) (TLC). Yield 45% (600 mg) EXAMPLE 3 N-heptyl-geneserine L-tartrate(CHF 2060). To a solution of 0,400 g of the product obtained in example 2 or in example 3 in 11,2 ml of anhydrous degased isopropyl ether, a previously prepared solution of 0,160 g of L-tartaric acid in anhydrous degased iso- propanol (3,2 ml) is added. The reaction mixture is re- acted until a clear solution is obtained, then 8 ml of anhydrous degased isopropyl ether are added and crystal formation starts. After other 2 hour stirring, the ob¬ tained solid is filtered, washing with some isopropyl ether. Yield = 60% (340 mg). EXAMPLE 4 N-heptyl-geneserine salicylate. A solution of 0,5 g of the product obtained in examples 1 and 2, in degased ethyl ether (15 ml) is ad- ded to a solution of salicylic acid (0,18 g) in 15 ml of degased ethyl ether, then the volume is left to de¬ crease upon slow evaporation. After 48 hours, a white solid forms which is filtered and dried under vacuum at 30 β C. Yield = 30% (200 g). EXAMPLE 5 a) Geneseroline. To a solution of 1 g of geneserine in 70 ml of anhydrous degased ethanol, 10 mg of sodium are added under nitrogen atmosphere. The reaction mixture is hea¬ ted to 40 β C and left under stirring at this temperature for 1 hour. When the reaction is over, solvent is eva¬ porated off under vacuum at 30 β C. The residue is trea¬ ted with 10% HCl (40 ml) and extracted with chloroform (3 x 50 ml). The combined organic solutions are washed with a NaCl saturated aqueous solution, dried over so- dium sulfate and evaporated under vacuum at room tempe¬ rature to give a red oil, in an about 60% yield. The oil is directly used for the subsequent reac¬ tion. TLC: Ethyl acetate/Chloroform/Hexane 3/1/1 Rf * __ 0,4. b) N-heptyl-geneserine. To a solution of 5 g of the product obtained in a) in 150 ml of anhydrous degased ethyl ether, 0,1 g of sodium are added and the reaction mixture is left to react for 1 hour at room temperature under nitrogen at¬ mosphere. Then N-heptyl-imidazol-urea, obtained accor¬ ding to the example 1(b) (4,85 g), dissolved in 10 ml of anhydrous degased ethyl ether is added, during about 30 minutes. After a day at room temperature, the ether solution is washed with 100 ml of water, dried over so¬ dium sulfate and evaporated under vacuum at 30°C. The obtained oil is purified by preparative TLC eluting with ethyl ether/triethylamine 40/1. The product is extracted from silica with chloro- form/ethanol 9,5/0,5, and it is obtained evaporating the solution under vacuum, at room temperature. A colourless oil is obtained in a 50% yield (4 g). TLC: Ethyl ether/Triethylamine 40/1 Rf = 0,8. EXAMPLE 6 a) Eseroline. A solution of 10 g of eserine in 40 ml of 37% HCl is refluxed under stirring. After 2 hours the greenish solution is evaporated off under vacuum at 70°C and the resulting oil is dissolved with 100 ml of water and treated with aq. ammonia to pH = 5. The solution is evaporated under vacuum at 70 β C to incipient precipitation, cooled and filtered. The obtained white solid is washed with acetone and ethyl ether, and dried under vacuum at 50°C. Yeld 86% (8.0 g) as hydrochloride. The base is obtained by addition of cone. aq. ammonia to an aqueous solution of the hydrochloride, saturation with NaCl and extraction with ethyl ether. The organic layer is dried over Na 2 S0., filtered and evaporated under vacuum at 25°C, to obtain a white crystalline solid in a 80% yield (5.5 g). b) N-Heptyleserine. 114 mg of sodium (50 wt % dispersion in paraffin) is added to a solution of 1.8 g of the product obtained according to a) in 100 ml of anhydrous ethyl ether, under nitrogen atmosphere. The mixture is allowed to stir to the complete dissolution, then a solution of 1.28 g of heptylisocianate in 30 ml of ethyl ether is added dropwise at room temperature. After one hour, NH.C1 (2 g) is added and the resulting mixture is stirred for half an hour, then washed with 30 ml of water; the organic layer is dried over Na 2 SO., filtered and evaporated under vacuum at 25 β C. The resulting orange oil is purified by F.C. (eluent chloroform : 90 = methanol : 10, stationary phase: silica gel, 30-60 urn) . An oily product is obtained, in a 85% yield (2.5 g). Purity 95%. c) N-Hepty1-geneserine. To a solution of 2.44 g of the product obtained in b) in 100 ml of methylene chloride a solution of 2.93 g of m-chloroperbenzoic acid (Fluka) in 40 ml of methylene chloride is added at room temperature. The solution is stirred for 30 min, then washed with 50 ml of a NaHCO, saturated solution and with 2 x 50 ml of a phosphate buffer (pH = 3), The organic layer is dried over Na 2 S0., filtered and evaporated under vacuum at room temperature. The resulting oil is extracted with 400 ml of n-hexane. The solvent is evaporated off under vacuum at 25°C to give a colourless oil, which solidifies on standing. Yield = 63% (1.6 g). d) N-Heptyl-geneserine hydrochloride. To a solution of 0.8 g of the product obtained in c) in 50 ml of ethyl ether a little excess of ethereal hydrochloric acid is added under stirring at 0°C. The resulting mixture is allowed to stir for an hour at 0 β C, then is decanted and the viscous oil is dissolved in methylene chloride. The solution is evaporated under vacuum at room temperature to give a solid foam, which is stored in freezer. Yield = 80% (0.7 g) TLC: Chloroform/methanol/formic acid 90/5/5 Rf = 0.8 PHARMACOLOGICAL ACTIVITY 1. Acetylcholinesterase inhibition The time course of inhibition of acetylcholinesterase (AchE) in the brain was assessed in male CrliCD (SD) BR rats (Charles River Italia), weighing between 150-250 g. The test substances were administered by s.c. route, dissolved in 2 ml/kg of sterile saline. 9 animals/group/time were used. Controls received the vehicle only. At various intervals (10 - 60 - 120 - 240 min) after administration the rats were sacrificed by decapitation and the brains were rapidly removed, weighed and immediately placed in 1 ml of phosphate buffer 0.1 M, pH 8.0, added with 1% Triton 100 (Merck). After homogenization and centrifugation at 19943 g for 15 min at 4 β C the surnatant was separated and used for the determination of AchE activity according to the acetyltiocholine method described by Ellmann (Ellman G.L. et al. , Biochem. Pharmacol. 7, 88, 1961). The activity concentrations obtained (ϋ/1 surnatant) were individually corrected for the brain weight. TABLE 1 Brain acetylcholinesterase in the rat after treatment with CHF 2060 and the reference compounds. Compounds were given by s.c. route, dissolved in 2 ml/kg of saline. Brains were homogenized in 2 ml of phosphate buffer 0.1 M, pH 8.0 added with 1% Triton 100. AchE activity was determined in the surnatant after centrifugation. Concentrations values were corrected for the brain weight. Statistical significance vs control ("t" Student's test): * P = 0.05; ** P < 0.01 Dose 10 min. 60 min. TREATMENT mg/kg s.c, U/l surn. % inhib, U/l surn. % inhib. Vehicle CHF 2060 - (continued) - TABLE 1 - (continued) - Dose 120 min. 240 min. TREATMENT mg/kg s.c, U/l surn. % inhib, U/l surn. % inhib. Vehicle CHF 2060 TABLE 2 Kinetic peirameters of the inhibition of brain acetylcholinesterase in the rat after s.c. administration. Dose Max AUC 0-4 h TREATMENT mg/kg T max % inhib. % inib. hr CHF 2060 9 _>240 min, 45 127 27 __240 min, 68 190 L Geneserine tartrate 10-60 min, 53-57 133 Physostigmine 0.4 10 min. 53 135 Hepthyl physostigmine tartrate 1 60 min. 54 178 0.3 94 Tmax = time of the maximal ihnibition 2. Results The brain AchE concentration values are shown in table 1, while the time course of the inhibition of the enzyme is depicted in fig. 1. A comparison between the kinetic parameters of the AchE inhibition is shown in table 2. The results obtained indicate that CHF 2060 is a long-lasting inhibitor of brain AchE. The effect appears to increase gradually during the 4 hrs following the treatment. A significant inhibition (29-45%; P< 0.001) is found 1 hr after administration. Within 4 hrs of treatment the effect is increased over a factor of 1.5-1.6 in respect to those observed at the first hour. Geneserine tartrate and physostigmine, at doses producing effects comparable (both in term of AUC and maximum inhibition) to those of 9 mg/kg CHF 2060, resulted in a more rapid effect, that peaks at 10-60 min., but it is reduced over a factor of 1.5-2 120 min. after the treatment. This effect disappears after 240 min. Comparing the kinetics of the effects produced by the new AchE inhibitor Hepthyl physostigmine tartrate (HPYS) with those obtained when administering CHF 2060 at a dose able to induce similar AUC "inhibition vs time" values (i.e. 1 vs 27 mg/kg), it is still evident that CHF 2060 exerts a more sustained action. In fact while the effect provoked by HPYS are reduced by a factor of 1.4 between 120 and 240 min, those observed after CHF 2060-treament are increased by the same factor in the same time interval.

Claims: CLAIMS 1. Compounds of formula I: wherein R is a straight or branched C 2 -C 2Q alkyl group, a C,-C 7 cycloalkyl group, a phenyl or benzyl group, op¬ tionally substituted with C.-C. alkyl groups, halogen atoms, C,-C 4 alkoxy groups. 2. Compounds according to claim 1 in which R is a straight or branched alkyl group having 4 to 12 carbon atoms. 3. A compound according to claim 1 or 2 in which R is n-heptyl. 4. The salts of the compounds of claims 1-3 with or¬ ganic or inorganic non-toxic salts. 5. The salts according to claim 4 in which the orga¬ nic acid is selected from tartaric acid and salicylic acid. 6. Pharmaceutical compositions containing as the ac¬ tive ingredient one compound of claims 1-5 in admixture with a compatible carrier. 7. The use of the compounds of claims 1-5 for the preparation of a medicament having cholinesterase-inhi- biting activity.

Inventors: CHIESI PAOLO, DEL CANALE MAURIZIO, GHIDINI ELEONORA, SERVADIO VITTORINO, CHIESI, PAOLO, DEL CANALE, MAURIZIO, GHIDINI, ELEONORA, SERVADIO, VITTORINO
Applicants: CHIESI FARMA SPA, CHIESI FARMACEUTICI S.P.A.
Application year: 1992
Main classification: C07D498
IPC codes: A61K31, A61P25, A61P43, C07D498