O-ALKANOYL DERIVATIVES OF 3-AMINO-2-HYDROXYPROPANESULFONIC ACID HAVING ANTICONVULSIVANT ACTIVITY AND PHARMACEUTICAL COMPOSITIONS CONTAINING SAME FOR THE THERAPEUTICAL TREATMENT OF EPILEPSY

Abstract: O-alkanoyl derivatives of 3-amino-2-hydroxy­ propanesulfonic acid having general formula H₃N CH₂ CH₂SO₃ wherein R is alkanoyl having 2-5 carbon atoms and the phar­ macologically acceptable salts thereof are endowed with po­ tent anticonvulsivant activity.

Description: The present invention relates to novel 3-APS (3-aminopropanesulfonic acid) derivatives having anticonvulsivant activity and the pharmaceutical compositions containing same for the therapeutical treatment of epilepsy. More specifically, the compounds of the present invention are O-alkanoyl derivatives of 3-amino-2-hydroxy propanesulfonic acid having general formula (I): wherein R is alkanoyl having 2-5 carbon atoms and the pharmacologically acceptable salts thereof. Preferably, R is acetyl, propionyl or butyryl. Clearly, the pharmacologically acceptable salts of the compound formula (I) have formula (Ia) wherein A⁻ is anion of the corresponding pharmacologically acceptable salt. For instance, A⁻ is Cl⁻. The potent antiepileptic activity of 3-APS in some test models has long been known. 3-APS is structurally related to both GABA (gamma-aminobutyric acid) and taurine and possesses chemical electrophysiological and biochemical properties strikingly similar to GABA and GABA-agonists. It has furthermore been shown that compounds capable of increasing GABA concentration in brain by blocking its enzyme degradation, possess antiepileptic activity. GABA itself has successfully been used in some epilepsy cases. However, neither GABA nor 3-APS easily cross the blood-brain barrier and consequently do not enter the central nervous system to any appreciable degree following oral or parenteral administration. It has been found that the 3-APS derivatives of the present invention are capable of inducing an anticonvulsive effect more potent than that of 3-APS when they are administered via the usual oral or parenteral routes. Compounds structurally similar to those of the present invention are known already. As the closest compound, L-3-amino-2-hydroxypropanesulfonic acid should be cited. This compound is a naturally-occuring substance and, in fact, it has been isolated from the red alga Polysiphonia fastigiata (Wickberg B., Acta Chem.Scand. 11 , 506 (1957). However, well before its isolation as a natural product, 3-amino-2-hydroxypropanesulfonic acid had been synthesized (Shigeru Tsunoo, Ber. 68, 1334-41,1935) from ammonia and 3-chloro-2-hydroxypropanesulfonic acid, that -in turn- had been obtained by reacting epichlorohydrin with sodium bisulfite. As disclosed by Shigeru Tsunoo et al. in Jap. J. Pharmacol. 14 , 393-400 (1964), thorough pharmacological searches were carried out in order to determine the activity of 3-amino-2-hydroxypropanesulfonic acid on the frog isolated heart as well as on the cardiac activity, blood pressure and breathing in dogs (Koizuka et al., Showa Med. J. 4, 91 (1942). Further searches were carried out with a view to studying the vasal action of this compound and its effects on adrenaline action (Tsuchida, Showa Med. J. 10 , 280-290 (1950). N-alkyl derivatives of the 3-amino-2-hydroxypropanesulfonic acid and salts thereof, e.g. with alkali metals, are also known. Thus, for example, the British patent 1,419,097 to Procter & Gamble Ltd., discloses a process for producing quaternary ammonium compounds containing a long-chain lipophilic group, wherein an organic chloride of the general formula R₁ Cl in which R₁ is a primary alkyl radical from 8 to 20 carbon atoms is reacted in the presence of iodide ions, with a substituted tertiary amine of the general formula in which R₂ and R₃, which may be identical or different, are each an alkyl group having 1 to 6 carbon atoms and M is a metal cation, preferably sodium or potassium. The resulting quaternary ammonium compounds are useful as surfactants. Further analogous compounds are e.g. disclosed in "Soap based detergent formulations: XII Alternate synthesis of surface active sulfobetaines", J.Am. Oil Chem.Soc. 53 , n.2 60-63 (1976). All such compounds are useful as surfactants in detergent compositions. The relevant prior art can, therefore, be summarized as follows: With regard to the compound which is the closest, from a structural viewpoint, to the compounds of the present invention, i.e. 3-amino-2-hydroxypropanesulfonic acid, its pharmacological properties in the cardiovascular field only have been examined, whilst its quaternary ammonium derivatives have been shown to possess utility as surfactants. The pharmacological properties on the central nervous system have not been investigated for anyone of these known compounds. On the other hand, it does not appear that the O-esters of the 3-amino-2-hydroxypropanesulfonic acid of the present invention have ever been disclosed. Consequently, the compound that is the structurally closest one to the compounds of the present invention and whose anticonvulsivant properties have been disclosed is 3-APS. The activity of the compounds of the present invention is, however, unexpectedly superior to that of 3-APS. The compounds of the present invention are prepared via known procedures: 3-amino-2-hydroxypropanesulfonic acid, prepared e.g. via the method disclosed in the above mentioned Ber. 68 , 1334-1341 (1935), is subjected to Schotten-Bauman acylation. The overall reaction scheme is as follows: The following non-limiting examples illustrate the preparation of some of the compounds of the invention. Example 1 Preparation of 3-amino-2-acetyloxy propanesulfonic acid (ST549). 13.5 g (0.146 moles) of epichlorohydrin were added to a solution of 15.26 g (0.08 moles) of sodium bisulfite in 45 milliliters of water. The reaction mixture was refluxed under stirring for 3 hours. Upon cooling first to room temperature and then to 0°C-5°C, a white solid (8 g) precipitated consisting of sodium 3-chloro-2-hydroxypropanesulfonate which was converted in the corresponding free acid with a strongly acidic resin (IR 120). Following concentration of the acid eluate, 7.5 g of 3-chloro-2-hydroxypropanesulfonic acid were obtained that were dissolved in 120 milliliters of conc.ammonia. The resulting solution was reacted at the reflux temperature overnight and then concentrated to dryness. The raw residue was purified with methanol. 5.3 g of 3-amino-2-hydroxypropanesulfonic acid were obtained. These 5.3 g of acid, dissolved in 9 milliliters of trifluoroacetic acid, were reacted with 24 milliliters of acetyl chloride under stirring at 50°C overnight. The reaction mixture was poured dropwise in 400 milliliters of ethyl ether. A white precipitate formed that, following decantation of the ether phase, was taken up with methanol and again precipitated with ether. 3 g of 3-amino-2-acetyloxy propanesulfonic acid were thus obtained. M.P.: 199-202°C TLC (CHCl₃, MeOH, NH₄OH, H₂O, 55:35:5:5) Example 2 Preparation of 3-amino-2-butanoyloxypropanesulfonic acid hydrochloride (ST 477). 10.3 g (0.054 moles) of sodium bisulfite were added to a solution of epichlorohydrin (10 g; 0.108 moles) in 30 milliliters of water. The reaction mixture was refluxed under mechanical stirring for 3 hours. Upon cooling, a precipitate formed that was shown to be the sodium salt of 3-chloro-2-hydroxypropanesulfonic acid (8.8 g; yield: about 46%). The product was chromatographed on IRC 50 resin (H⁺ form) by eluting with H₂O (column diameter: 2.5 cm). The ratio 1:14 (g/ml) was maintained. 7 g of 3-chloro-2-hydroxypropanesulfonic acid, m.p. 250-251°C, were obtained. A solution of 10 g (0.057 moles) of 3-chloro-2-hydroxypropanelsulfonic acid in 100 milliliters of conc. NH₄OH was reacted under magnetic stirring at 100°C overnight. Following evaporation of the solution, the residue was crystallized from H₂O -acetone, m.p.295-6°C. The compound, dissolved in H₂O and 6N HCl to convert it into its hydrochloride, was oven-dried in the presence of NaOH pellets and directly used in the subsequent reaction. 8.33 g (yield 76%) were obtained. To a suspension of 2.0 g of hydrochloride in 40 milliliters of trifluoroacetic acid, 73.8 g (0.7 moles) of butyl chloride were added. The reaction mixture was heated up to 50°C and kept under magnetic stirring for 18 hours. After it had been cooled to room temperature the mixtured was filtered and the filtrate added dropwise to an Erlenmeyer flask containing about 700 milliliters of ethyl ether. A white precipitate formed which was again dissolved in methanol, filtered and re-precipitated with ether. Upon drying 7.3 g of a white, hygroscopic solid product, stable at pH ≦6.3 were obtained; above this temperature deacylation of the compound takes place. Example 3 Preparation of 3-amino-2-propionyloxy-1-propanesulfonic acid hydrochloride (ST 473). 3-amino-2-hydroxypropanesulfonic acid (prepared as described in Example 1) (9.48 g; 0.038 moles) was dissolved in 11 milliliters of trifluoroacetic acid. Propionyl chloride (47 cc; 0.48 moles) was added to the resulting mixture. The mixture was kept under magnetic stirring at 50°C overnight. After cooling to room temperature the mixture was filtered. Ethyl eter was added to the filtrate till complete precipitation of a solid product. The solid thus formed was filtered off and crystallized from acetone-ethyl ether. 2.7 g of a white hygroscopic compound were obtained. It was, therefore, impossible to measure its melting point. TLC: silica gel Rf: 0.7 PHARMACOLOGICAL TESTS Toxicity The toxicity tests were carried out on male and female Sprague Dawley rats which were orally administered ST549 at the doses of 150-450-1350 mg/10 ml/kg for 15 consecutive days; the control animals were administered the same volume of vehicle as the test animals. The compound did not affect either general health or behaviour of the animals. In all treated animals blood and urine parameters were unchanged with respect to the controls. Autopsy was performed at the end of the test and did not reveal either alterations or lesions to the main organs. Tolerability The tolerability test was carried out on male albino swiss mice weighing 22-24 g. The compound ST 549, dissolved in sterile saline and intravenously administered at neutral pH, was well tolerated at the dose of 1.4 g/kg. Anticonvulsivant tests Anticonvulsivant tests were carried out using cardiazol, strychnine and bicuculline at doses of 100 mg/10 ml/kg i.p., 0.73 mg/10 ml/kg s.c. and 2.38 mg/10 ml/kg s.c., respectively, chosen in such a way as to provoke death in 50% of the control animals. The tests were carried out in male albino swiss (Charles River) mice weighing 22-24 g. The compound under examination, dissolved in water, was i.p. administered 30 minutes before the convulsivant agent administration. As reference substance, 3-APS (200-400-800 mg/10 ml/kg i.p.) was used. As activity parameters the following were considered: latency time of first convulsion, percentage of animals exhibiting convulsions, death latency time and death rate. The test results relating to 3-APS are illustrated in Table 1. 3-APS at doses of 200,400 and 800 mg/10 ml/kg i.p. did not preserve animals from cardiazole-, strychnine-and bicuculline-induced death. At 400 mg/10 ml/kg the latency time of bicuculline-induced death significantly increased, while at 800 mg/kg the latency time of the bicuculline-induced first convulsion significantly increased. The test results relating to the compound under examination are illustrated in Table 2. ST 549, at a dose equimolar to 400 mg/10 ml/kg i.p. of 3-APS, preserved 100% animals from cardiazol-induced death; the lower dose equimolar to 200 mg/10 ml/kg of 3-APS) did not affect the relevant parameters. At the doses equimolar to 400 and 200 mg/10 ml/kg i.p. of 3-APS, ST 549 decreased bicuculline-induced death rate by 30% and preserved from convulsions the same percentage of animals. The lower dose significantly increased the latency time of strychnine-induced first convulsion and death. Antiepileptic activity test (FeCl₃-induced epilepsy model). Male albino Wistar rats weighing 250-300 g were used. The animals, anaesthetized with Nembutal Na (30 mg/kg e.p.), were stereotactically injected in their left ventral hippocampus one microliter of 0.55 M FeCl₃ solution (AP =-3.2; L=5.0; H=5.5 Pellegrino and Cushman, 1971). Ten minutes following injection, recording electrodes were implanted: in both ventral hippocampi, two millimeters below the FeCl₃ injection site (bipolars), bilaterally on the frontoparietal cortex (monopolars). Recording of cerebral bioelectric activity, carried out with an EEG OTE-Biomedica PF 14e recorder, began about one hour following FeCl₃ injection (when the animal, after the anaesthetic effect had subsided, had regained the straightening reflex) and lasted more than three hours on end. The epilepsy degree was assessed by calculating for each animal the number and duration in seconds of the seizures at 5-minute intervals during the whole recording span both in the hippocampus where the injection had been performed and in the contralateral cortex. Moreover, an "index of epileptization" was calculated as the mean product of seizure number times the duration of the seizures in each time interval. 500, 250 and 125 mg/kg of the compound under examination, dissolved in sterile saline, were intravenously administered at neutral pH ninety minutes following FeCl₃ injection. Three groups of control animals received, at the same time and via the same administration route as the test animals, an identical volume of vehicle. The results thus obtained show the antiepileptic activity of the compound assessed by examining the whole phenomenon as it evolves in time via the measure (carried out with the trapezoidal rule) of the area under the curve wherein the average number of seizures and their duration is plotted versus time. By comparing the areas relating to the controls with the areas relating to the treated animals via Mann-Whitney's "U" test, it was assessed that ST 549, at the tested doses, presented a statistically significant difference (P<0.05) with respect to the controls. Auricular electroshock Male albino Swiss mice weighing 22-24 g were used in this test. The electroshock conditions were the following: shock duration: 3 seconds; frequence: 100; pulse amplitude: 0.6 milliseconds, current intensity: 40 milliamperes. 400 and 800 mg/10 ml/kg of the compound under examination were administered via the intraperitoneal route 30 minutes before the electroshock. The tests results which illustrate the number of animals preserved from death provoked by maximal electroshock are shown in the following Table 3. Approximately 25-70 mg of a compound of general formula (I)/kg of body weight/day, was judges to be the appropriate dose for oral or parenteral administration. However, lower or higher doses, based on sound physician's judment can be administered. In practice, the compounds are orally or parenterally administered in any one of the usual pharmaceutical formulations which are prepared according to conventional procedures well-known to those skilled in pharmaceutical technology. These formulations comprise solid and liquid unit dosage forms, such as tablets, capsules and injectable forms, e.g. sterile solutions for ampules and vials.

Claims: A compound having general formula (I) wherein R is alkanoyl having 2-5 carbon atoms, and its pharmacologically acceptable salts. The compound of claim 1, wherein R is acetyl, propionyl of butyryl. As compound of claim 1, the compound An orally or parenterally administrable pharmaceutical composition for treating epilepsy comprising an amount therapeutically effective for inducing an anticonvulsivant effect in an epileptic patient of a compound of general formula (I) or an equivalent amount of a pharmacologically acceptable salt thereof, and a pharmaceutically acceptable excipient. The composition of claim 4, wherein the compound is the compound of claim 2. The composition of claim 4, wherein the compound is the compound of claim 3.

Inventors: BAGOLINI, CARLO ALBERTO, PACIFICI, LICIA, QUARESIMA, EMMA TERESA
Applicants: SIGMA TAU INDUSTRIE FARMACEUTICHE RIUNITE S.P.A.
Application year: 1988
Main classification: C07C309
IPC codes: A61K31, C07C301, A61P25, C07C67, C07C309