FR2627487A1 - Anti-epileptic valproic acid ester - 2:6 di:hydroxy methyl pyridine bis 2:propyl pentanoate - Google Patents

Abstract

2,6-pyridine dimethanol di-2-propyl pentanoate (pyridinol valproate) (I), and its salts, are new esp. (I) hydrochloride. Valproic acid is treated with thionyl chloride to form the acid chloride, and this is reacted with 1/2 a molar equivalent of 2,6-pyridine dimethanol. The reaction is usually effected in an organic solvent such as dioxan or dioxan/pyridine, at a temperature below 30 deg. C. USE/ADVANTAGE - The compound is an anti-epileptic agent with a very low toxicity and, unlike sodium valporate, it does not cause hepatic disorders.

Description

"New derivative of valproic acid, process for the preparation of this compound and the antiepileptic drug containing it"
The present invention relates to a new derivative of valproic acid, to a process for the preparation of this compound, as well as to an anti-epileptic medicament containing it.

 Epilepsy is a very serious condition of the central nervous system which has been well known for a long time; the convulsive seizures sometimes accompanied by the loss of consciousness that it causes can sometimes have dramatic consequences. It is for this reason essential to avoid the appearance of such crises in subjects suffering from epilepsy, thanks to suitable products which must most often be absorbed orally; these patients must be treated for life, and it is therefore essential that the drugs chosen are free of side effects as much as possible.

Among the most commonly used anti-epileptics, we can note 11 valproic acid, or 2 propylpentanoic or more precisely its sodium salt corresponding to the formula

 This compound has indeed proved to be a particularly effective antiepileptic which is characterized by an anti-convulsant activity in very varied types of epilepsy, an original mode of action in the central nervous system (increase in acid levels amino-butiric gamma) and an absence of hypnogenic effect.

 The biological tolerance of this product, although acceptable, is however not optimal and, in some cases, serious side effects have been noted, such as severe liver damage, which means that this medication should be strictly discouraged in case of acute or chronic hepatitis.

 Now, in accordance with the invention, it has been found that, surprisingly, certain derivatives of valproic acid had at least comparable anti-epileptic and anti-convulsant activity, while having a significantly reduced toxicity.

ou par les sels de ce composé.These compounds consist of pyridine di-2propylpentanoate 2-6 methanol or pyridinol valproate of formula

or by the salts of this compound.

Among these, we can especially note the pyridinol hydrochloride valproate which corresponds to the formula

 The invention also relates to a process for the preparation of the above-mentioned compounds.

 According to the invention, for the preparation of pyridinol valproate, in a first phase, valproic acid chloride is prepared, which is commercially available, and this compound is condensed with half a molar equivalent of pyridine. 2-6 dimethanol.

According to another characteristic of the invention, the chloride of valproic acid is prepared by reacting this acid with thionyl chloride, with stirring and maintaining the temperature at a value below -30 "C, in accordance with the formula

 To accelerate the reaction, a catalyst is preferably used, in particular consisting of grains of molecular sieve 3.

 To obtain an optimal yield, the reaction is continued for about five hours, before distilling the valpoic acid chloride obtained in vacuo.

 According to another characteristic of the invention, the chloride of valpoic acid and pyridine 2-6 dimethanol is condensed in an organic solvent, in particular in dioxane or a mixture of dioxane and pyridine with stirring and maintaining temperature below 30 "C.

The reaction is carried out according to the following formula

 To improve the yield, the reaction is generally continued, still with stirring, for a period of 10 to 12 hours and at room temperature.

 At this time, it is necessary to isolate the pyridinol valproate present in the reaction medium.

 For this purpose, and according to another characteristic of the invention, the condensation product is brought to dryness under vacuum, it is drowned in ice water and it is extracted with dichloromethane before being brought to dryness again under vacuum.

 It has been found that the pyridinol valproate thus obtained is insoluble in water; to obtain a product which is easy to use in the pharmaceutical industry, it is therefore necessary to prepare one of its compounds, preferably pyridinol valproate hydrochloride.

 For this, and according to another characteristic of the invention, the pyridinol valproate is treated with a mixture of methanol and concentrated hydrochloric acid, the product thus obtained is brought to dryness, these procedures are repeated if necessary operations, and the final product is recrystallized from a methanol-ether-cycloheaxne mixture, before wringing it out, washing it, in particular with ether and drying it under vacuum.

 These operations make it possible to obtain a liquid which crystallizes after a few hours.

The invention also relates to an anti-epileptic medicament which contains as active substance pyridinol valproate hydrochloride which corresponds to the formula

 This medication may be in the form of an oral solution or tablets.

 In the case of an oral solution, it preferably contains between 100 and 500 milligrams of pyridinol valproate hydrochloride per milliliter of solution, and, the excipient is generally chosen from urea, sodium hydroxide, and purified water or mixtures of these products.

 In the case of a tablet, it generally contains between 100 and 700 milligrams of pyridinol valproate hydrochloride, and, preferably coated with a resistant fatty coating. Among the excipients which can be used during the manufacture of such tablets, one can note calcium silicate, poly vidone, magnesium stearate, talc, polyoxyethylene glycol, corn starch, oxide of titanium, yellow iron oxide, cellulose acetylphthalate, or diethyl phthalate.

 The list of excipients mentioned above is of course not limitative of the invention, whether the medicament is in the form of tablet or of an oral solution.

 The medicament according to the invention is generally administered to adolescents or to adults at a rate of 20 to 30 milligrams per kilo and per 24 hours. This amount is most often divided into two or three doses, preferably during meals.

The characteristics of the manufacturing process which is the subject of the invention, as well as the anti-epileptic properties thereof, will be explained below using the following examples
EXAMPLE 1 Preparation of pyridinol valproate
hydrochloride
In a first phase, in a 250 ml three-necked flask with ascending coolant, bulb to be introduced, atmosphere of dry nitrogen, ice bath and magnetic stirring, 50 grams of 2propylpentanoic acid (Janssen) are successively introduced with stirring and dropwise. drop 45 grams of thionyl chloride while keeping the temperature below 30 C. Add 3 grains of .....

 A gas evolution is then observed. Stirring is continued for 5 hours at a temperature below 300C.

 Then, vacuum distillation while controlling the vacuum. There is a boiling point of 1150C under 240 millimeters of mercury.

 43.2 grams of pure valproic acid chloride are thus isolated.

 In a second phase1, 17 grams of commercial pyridine 2-6 dimethanol (Aldrich) are introduced into a 500 milliliter three-necked flask with ampoule to be introduced, magnetic stirring, thermometer and atmosphere of dry nitrogen. and the 43.2 grams of val proic acid chloride previously obtained.

 70 milliliters of anhydrous dioxane are added dropwise, maintaining the temperature below 30 C, 130 milliliters of anhydrous pyridine.

 During this introduction, we can observe a white crystallization of pyridinium hydrochloride; another 100 milliliters of anhydrous dioxane are added to avoid solidification.

 This reaction mixture is kept under stirring overnight at room temperature.

 In a third phase, the reaction mixture is taken up and brought to dryness under deep vacuum; it is then drowned in ice water: 300 milliliters then it is extracted with five times 100 milliliters of dichloromethane; it is then washed with twice 100 milliliters of water.

 The product obtained is brought to dryness under vacuum and 42.2 grams of an amber liquid are obtained, which it is not possible to crystallize.

 In a fourth phase, 200 ml of methanol containing 20 ml of concentrated hydrochloric acid are added to this liquid; the mixture thus obtained is brought to dry; it is taken up twice in methanol and it is brought to dry each time before being drawn under vacuum to remove the water.

 A liquid is thus obtained which crystallizes after a few hours. This liquid is recrystallized from a methanol-ether-cyclohexane mixture, then it is drained, washed with ether and dried under vacuum.

This gives 38.2 grams of a white product crystallized in waxy flakes which is difficult to dissolve because it does not get wet. This product looks like a fatty substance and its solution is very acidic (which is normal since it is a salt of a strong acid and a weak base). It was verified that the product obtained was indeed pyridinol valproate hydrochloride by different methods of analysis
- Thin-layer chromotography
The product obtained was studied using as stationary phase Merck plastic silica, and as mobile phase CH2C12CH2C12 at 2% NaOH; for the revelation, UV radiation of wavelength 254 μm was used and sprayed with Dragendorff reagent.

 After revelation, a single task was obtained corresponding to an rF value equal to 0.6.

- Nuclear magnetic resonance
Proton NMR spectra at 60 bHz in
CDCl3 were established respectively for val proic acid and pyridinol valproate hydrochloride the spectra obtained are shown in Figures 1 and 2 respectively, and correspond perfectly to the expected structure.

- Mass spectrometry
The mass spectrum of pyridinol hydrochloride valproate is shown in Figure 3 and is also in agreement with the assumed structure (EM = 391, correct fragmentation, based).

- Infrared spectroscopy
The IR spectrum of pyridinol hydrochloride valproate is shown in Figure 4; we can note the presence of a carbonyl band at 1738 cm-1 which is characteristic of an ester.

 For the product obtained, the instant melting point is equal to 76 ° C and the slow melting point to 55-C.

 The above results prove that the product finally obtained by the above-mentioned method is indeed pyridinol valproate hydrochloride.

EXAMPLE 2 Study of the physiological properties of
pyridinol valproate hydrochloride
The various results gathered above were obtained following experiments carried out by Professor Jean Jacques SERANO within the framework of the Pharmacodynamics Laboratory of the Faculty of Pharmacy of MONTPELLIER.

1 ') Toxicity
The experiments were carried out on EOPS mice, of SWISS strain of female sex, maintained in a pet shop where the temperature was +22 + 1-C, where the humidity was 60% + 10% and where the lighting was adjusted to 12 hours.

 At the time of treatment, the animals observed a non-watered fast of approximately 18 hours, and drinking water and food were not given until 3 hours after treatment.

 Pyridinol hydrochloride valproate was emulsified in 3% gummy water and then administered by esophageal tube at a rate of 10 ml / kg.

The animals were divided into four groups to which the following doses were administered
- group 1: 1000 mg / kg of pyridinol valproate hydrochloride,
- group 2: 1500 mg / kg of py ridinol valproate hydrochloride,
- group 3: 2000 mg / kg of pyridinol valproate hydrochloride,
- group 4: 2500 mg / kg of pyridinol valproate hydrochloride.

 Observation of the animals was carried out after 30 minutes, 60 minutes and then every hour during the 6 hours following the treatment.

 The behaviors were noted daily for the duration of the trial.

 The animals were kept under observation for 15 days and a body weighing was carried out at the start of the treatment, then after 5, 10 and 15 days.

 No mortality was observed during the test in the treated animals.

 No toxic symptoms were noted in the hours after treatment or the following days.

 Statistical analysis at the probability threshold PO, 05, did not show any significant difference in the weight growth of the animals treated at the doses of 1000 mg / kg, 1500 mg / kg, 2000 mg / kg and 2500 mg / kg.

 The lethal dose 50 of pyridinol valproate hydrochloride was therefore found to be greater than 2500 mg / kg.

 Under the same experimental conditions, and in the same animal species, it has been determined that the lethal dose 50 of sodium valproate orally is of the order of 850 mg / kg.

 These results show that pyridinol hydrochloride valproate is significantly less toxic than sodium valproate.

2) Potentiation of sleep
WINTER test
It is known that sleep induced by a relatively low dose of a hypnotic is prolonged under the effect of pre-treatment with a neuropleptic. The latency and the duration of sleep are appreciated for all animals.

We used rats for testing
EOPS, of WISTAR strain maintained in a pet store where the temperature was 22 + 1-C, where the humidity was 60% + 10% and where the illumination was 12 hours.

After observing a non-water fast for a period of approximately 18 hours, the rats were subdivided into five batches which were received, respectively, by esophageal probe.
- lot 1: 3% gummy water
- lot 2. pyridinol valproate hydrochloride at 100 mg / kg,
- batch 3: pyridinol valproate hydrochloride at 200 mg / kg, - batch 4: sodium vaitproate at 100.mg / kg,
- lot 5: sodium valproate at 200 mg / kg.

 This oral treatment was carried out at time 0 in a volume of 10 ml / kg.

 At time 30 minutes, the animals were injected, intraperitoneally and at a rate of 5 ml / kg of pentobarbital (hypnotic) at a dose of 40 mg / kg.

 The animals were then classified into individual boxes and heated to avoid any cooling.

For each of the rats in each batch, we studied
- sleep. which is appreciated by the disappearance of the righting reflex: the animal placed on the back is unable to change position and recover on its legs,
- the latency time which is the time of falling asleep. It is the time separating the administration of the hypnotic and the disappearance of the righting reflex,
- the duration of sleep, which is the time between the disappearance and the return of the righting reflex.

 From the results obtained for all the animals treated in each batch, the mean time to sleep, the average sleep time and the percentages of change in sleep time and sleep time were calculated.

 Under the above-mentioned experimental conditions, pyridinol hydrochloride valproate potentiated the induced sleep highly significantly at the dose of 200 mg / kg (92.36%); at a dose of 100 mg / kg, a non-significant variation of 19.44% was obtained.

 The sodium valproate studied at the same doses did not significantly modify the induced sleep time. 2.16% was obtained at the 100 mg / kg dose and 38.12% at the 200 mg / kg dose.

 Neither pyridinol hydrochloride valproate nor sodium valproate significantly increased the latency period when falling asleep.

39) Protection against a substance
convulsant
It is known that the subcutaneous injection of pentylenetetrazol triggers convulsive attacks characterized by clonal-toxic attacks which are often fatal.

 The experiments were again carried out on EOPS mice of the SWISS strain maintained in a pet store where the temperature was 22 + 1'C, where the humidity was 60 + 10% and where the illumination was adjusted to 12 hours .

After observing a non-water fast of approximately 18 hours, the animals were subdivided into nine batches which were treated at time zero as follows
- lot 1: 4-hour control - having received 10 ml / kg of 3% gummy water,
- lot 2: pyridinol valproate hydrochloride 4 hours, 100 mg / kg - having received 10 ml / kg of emulsion in gummy water;
- batch 3: sodium valproate 4 hours, 100 ml / kg - having received 10 ml / kg of solution in gummy water,
- batch 4: control 30 minutes - having received 10 ml / kg of 3% gummy water
- lot 5: pyridinol valproate hydrochloride 30 minutes, 200 ml / kg - having received 10 ml / kg of emulsion in 11 gummy water at 3% pyridinol valproate hydrochloride,
- lot 6: sodium valproate 30 minutes 200 ml / kg - having received 10 ml / kg of sodium valproate solution;
- lot 7: 4-hour control - having received 10 ml / kg of 3% gummy water,
- lot 8: pyridinol valproate hydrochloride 4 hours, 200 mg / kg - having received 10 ml / kg of emulsion of pyridinol valproate hydrochloride in 3% gummy water,
- batch 9: sodium valproate 4 hours, 200 ml / kg - having received 10 ml / kg of solution of sodium valproate in gummy water at 3%.

At time 30 minutes, cardiazol was injected subcutaneously at a dose of 120 ml / kg, at a rate of 10 ml / kg in the following batches
- lot 4: witness
- lot 5: pyridinol valproate hydrochloride 200 mg / kg,
- lot 6: sodium valproate 200 mg / kg.

At time 4 hours, cardiazol was injected subcutaneously at a dose of 120 ml / kg at a rate of 10 ml / kg to the following batches
- lot 1: witness
- lot 2: pyridinol valproate hydrochloride 100 mg / kg
- lot 3: sodium valproate 100 ml / kg
- lot 7: witness
- lot 8: pyridinol valproate hydrochloride 200 ml / kg
- lot 9: sodium valproate 200 mg / kg.

 For each animal in each batch, the time of the first attack and the time of death were noted, and the latency of the first attack, the latency of death and the percentage of survival were calculated.

For lots treated with cardiazol, 30 minutes after oral administration, the following experimental results were noted
The onset time of the first attack was delayed by 43.31% for pyridinol valproate hydrochloride and 68.78% for sodium valproate.

 The comparative study between the two treatments was not found to be significant.

 Treatment with sodium valproate did not significantly potentiate the time of death (28.88%).

 Treatment with pyridinol valproate hydrochloride did not potentiate the time of death (o%).

 The time of death compared to pyridinol hydrochloride valproate was significantly delayed by sodium valproate at a dose of 200 ml / kg.

 70% survival was obtained with the sodium valproate treatment and 40% survival with the pyridinol valproate hydrochloride treatment.

In the case of batches treated with cardiazol 4 hours after oral administration, the following results were noted
The seizure was delayed not significantly during the treatments carried out at the dose of 100 mg / kg. The elongation percentages obtained are 24.12% for pyridinol hydrochloride valproate and 0% for sodium valproate.

 The comparative statistical study between the two products indicated an extension of the time from the onset of the first attack by 40.30% to the limit of significance in favor of pyridinol valproate hydrochloride.

 Death was delayed identically and not significantly for the two treatments performed.

Elongation percentages of 27.17% were observed for pyridinol valproate hydrochloride at 100 mg / kg and 28.98% for sodium valproate.

 20% survival was obtained with sodium valproate treatment.

 For the 200 mg / kg dose, the attack was not significantly delayed with the two treatments (0% for pyridinol valproate hydrochloride and 8.43% for sodium vaiproate).

 The time of death was delayed for the two treatments studied. 51.89% of the elongation time was obtained with pyridinol chlorhy drated valproate, which is not significant and 110.19% of the elongation time with sodium valproate which is significant.

 It should however be noted that the comparative statistical study between the two treatments is not significant.

 Furthermore, 10% survival was obtained in the control animals, 20% in the animals treated with pyridinol valproate hydrochloride and 10% in animals treated with sodium valproate.

 During the aforementioned series of experiments, the two products tested: pyridinol hydrochloride valproate and sodium valproate presented the same activity profile with regard to the protection of the seizure with cardiazol as well as the percentage of mortality.

In conclusion, under the above experimental conditions ,. pyridinol valproate hydrochloride has shown:
- an LD50 greater than 2500 ml / kg. Pyridinol hydrochloride valproate is much less toxic than sodium valproate, the LD50 of which was determined at 850 ml / kg under the same experimental conditions.

 - a highly significant increase in induced sleep time during the WINTER test.

This potentiation is greater than that obtained with the same dose of sodium valproate.

 - an activity comparable to that of sodium valproate during protection against the convulsive seizure with cardizol.

 Examination of these results shows that the therapeutic index is clearly in favor of the valproic acid derivative.

Claims (1)

 RESELL ICATIONS  3 New derivative of valproic or 2-propylpentanoic acid characterized in that it consists of 2-6 pyridine di-2-propylpentanoate dimethanol or pyridinol valproate of formula

 or by a salt of this compound.  2 ') New valproic acid derivative according to claim 1, characterized in that it consists of pyridinol hydrochloride valproate corresponding to the formula

 3 ') Process for the preparation of pyridinol valproate according to claim 1, characterized in that chloride of valproic acid is prepared and this compound is condensed with 1/2 molar equivalent of pyridine 2-6-dimethanol .  4 ') Method according to claim 3, characterized in that the chloride of valproic acid is prepared by reacting this acid with thionyl chloride with stirring and maintaining the temperature at a value below 30'C .  5 ') A method according to any one of claims 3 and 4, characterized in that one carries out the condensation of the chloride of valproic acid and pyridine 2-6-dimethanol in an organic solvent, in particular in dioxane or a mixture of dioxane and pyridine, with stirring and keeping the temperature below 30 C.  6 ') Process according to claim 5, characterized in that to isolate the pyridinol valproate, the condensation product is brought to dryness under vacuum, it is drowned in ice water and it is extracted with dichloromethane before bring dry again under vacuum.  7 ") Process according to any one of claims 3 to 6, for the preparation of pyridinol hydrochloride valproate characterized in that the pyridinol valproate is treated with a mixture of methanol and concentrated hydrochloric acid, it is brought to dry the product thus obtained, these operations are repeated if necessary at least once and the final product is recrystallized from a methanol-cyclohexane ether mixture before drying, washing in particular with ether and drying under vacuum .  8 ') Anti-epileptic drug characterized in that it contains as active substance pyridinol valproate hydrochloride corresponding to the formula

 90) An anti-epileptic drug according to claim 8, characterized in that it is in the form of an oral solution containing between 100 and 500 mg of active substance per ml of solution.  1O) Antiepileptic drug according to claim 8, characterized in that it is in the form of tablets each containing between 100 and 700 mg of active substance.