NO831737L - PROCEDURE FOR THE PREPARATION OF INDOLO-NAPHYRIDINE INGREDIATES - Google Patents

Description

The present invention relates to a method for separating enantiomers of 2,3,3a,4,5,6-hexahydro-1H-indolej3,2,1-de_7/naph tyridine-1,5J7 and the distinctive feature of the method according to the invention is that a mixture of enantiomers of formula (I)

in the form of a base is reacted with one of the enantiomers of a chiral acid, one of the two diastereoisomeric salts thus obtained is separated by fractional crystallization and returned to the base form, and if desired, the base is converted into an addition salt with a pharmaceutically acceptable acid.

These and other features of the invention appear in the patent claims.

The French patent document No. 2,494,693 describes, among other things, the racemate of 2,3,3a,4,5,6-hexahydro-lH-indolo-</3, 2 , l-de^7/haf tyridine-1, 5l7 as corresponds to formula (I)

In the structure of this compound, the carbon atom in the 3a position is asymmetrically substituted and this leads to two optical antipodes.

Each of these two enantiomers can be isolated by preparing the addition salt of one of the optically active antipodes of a chiral acid such as, for example, bis-2, 3, (4-methyl-benzoyloxy)-butanoic acid, 8- or 10 -3-bromo-camphorsulfonic acid, 10-camphorsulfonic acid,

tartaric acid, N-(α-methylbenzyl)-phthalic acid monoamide, maleic acid or mandelic acid.

The salt formation takes place between normal temperature and the boiling temperature of the solvent from a mixture of enantiomers of formula (I), e.g. from the racemate, in the form of base, dissolved in a suitable solvent such as alcohol, preferably ethanol.

The two diastereoisomeric salts thus obtained are then separated by fractional crystallization.

After the separation, they can be separated from the chiral acid and returned to the addition salt by means of any physiologically tolerable acid.

An enantiomer of formula (I) can also be obtained from a particularly enriched base of one of the enantiomers, such as e.g. is written from the mother liquors from recrystallization of a mixture of the diastereoisomeric salts. The chiral acid used for the separation of such an enriched mixture is then the antipode of that which has allowed the attainment of said mixture.

The optical purity of isomers of formula (I) can be determined e.g. by gas phase (CPV) or liquid phase (CLHP) chromatography using a method described for amino acids by B. Halpern in Handbook of Derivatives for Chromatography, pages 457-476, published by K. Blau and G.S. King (Heyden).

The method consists in condensing the isomer of formula (I) with

(-)-Menthyl chloroformate of formula (II), prepared by the method described in the aforementioned reference

so that the corresponding menthyl carbamate is obtained. This latter, examined by CPV or CLHP chromatography, gives rise to a single peak if a single enantiomer of formula (II) is present and two peaks if the separation is incomplete.

The following examples illustrate the separation of the isomers of the compound of formula (I) and confirmation of their purity.

EXAMPLE 1 (+)-2,3,3a,4,5,6-hexahydro-1H-indolo/3,2,1-de_7/haf tyridine-1,5_/ and its methanesulfonate

a) Formation of diastereoisomeric salts with (+)-2, 3- bis-(4- methyl- benzoyloxy)- butanedioic acid

34.41 g of racemic 2,3,3a,4,5,6-hexahydro-1H-indolo/"3, 2, 1-deJ/ haftyridine-1-5_7 in the form of an oily base obtained according to Example 1 of French Patent Application No. 80.24727 in solution in 250 ml of absolute ethanol At ordinary temperature and with stirring slowly add 32.78 g of (+)-2 ,3-bis-(4-methyl-benzoyloxy)-butanedioic acid in solution in 250 ml of absolute ethanol. A copious precipitate forms even before the addition is complete. The mixture is then slowly heated to the reflux temperature, after which another 200 ml of ethanol is added to obtain complete dissolution of the crystals. Some insoluble crystals are removed by filtration, the filtrate is reheated and cooled to ordinary temperature. After a few hours' rest, the formed crystals are filtered on glass frit and dried under vacuum at 50° C. 43.56 g of white crystals are obtained.

b) Recrystallization

The crystals obtained in this way are recrystallized

several times from 95% ethanol. After each recrystallization, approximately 0.25 g of crystals are taken out and the base is released with the help of a dilute mixture of ammonia and chloroform and the rotatability is determined. After four recrystallizations, the rotatability of the base is stable and approximately £ ajp5 = + 63.29° (c = 1 in MeOH) .

The salt from which this base is released has a rotatability of approx

Z~ol7d= + 84.51° (c = 1 in MeOH).

c) The methanesulfonate

In a 250 ml Erlenmeyer flask equipped with magnetic

stirrer is placed 5.78 g of the salt obtained under b) with 100 ml of 10% ammonia and 100 ml of ethyl acetate. After stirring for a few minutes, the organic phase is separated, the aqueous phase is taken up in 100 ml of ethyl acetate, the two organic phases obtained are combined, washed with water, dried over magnesium sulfate and evaporated on a rotary evaporator and dried under vacuum. The base is then obtained in the form of 2.96 g of a mixture of white crystals and an oil.

In a 250 ml round flask with a magnetic stirrer, this base is dissolved in 60 ml of ethyl ether and the equivalent amount of methanesulfonic acid, namely 1.34 g, in solution in

15 ml of absolute ethanol. A copious precipitate is formed. Stirring is continued for half an hour at normal temperature, after which the crystals are filtered off on a glass frit and dried under vacuum at 50°C. A recrystallization from 60 ml of absolute hot ethanol, followed by a night's standing at ordinary temperature gives, after filtration and drying under vacuum, 3.03 g of crystals of methanesulfonate melting at 222-224°C. Turning ability:

Elemental analysis and analysis RMN and IR confirm the structure of the compounds.

d) Confirmation of purity

In a round flask of 100 ml equipped with magnetic

stirrer and a calcium chloride trap are placed 140 mg of ( + )-2, 3, 3a, 4, 5, 6-hexahydro-1H-indolo/3, 2, 1-de^/Jnaphthyridine-1,5.7 in solution in 10 ml of ethyl acetate with 66.7 mg (1 equivalent) of triethylamine and the mixture is cooled in an ice-mixed water bath. One then adds an equivalent of

(-)-Menthyl chloroformate in solution in toluene, or

-4

1 ml with 6.6 10 mol/ml, and stirring is continued in

15 min. at 0°C and then for 20 min. at normal temperature. Undissolved matter is filtered off and the organic phase is washed with water, then with an aqueous solution of 5% sodium bicarbonate and once more with water.

It is then dried over magnesium sulphate, evaporated on a rotary evaporator and then under vacuum. 251 mg of a yellowish oil is obtained, which is converted into a solution with 0.1 mg/ml in ethyl acetate. Gas chromatography of this solution gives a curve with a single peak.

EXAMPLE 2 (-)-2,3,3a,4,5,6-hexahydro-1H-indolo[3,2,1-deJynaf tyridine-1,^)7

a) release of the base from a mother liquor from recrystallization of dextrorotatory isomer in the form of

2,3-bis(4-methyl-benzoyloxy)butanedioate

In a rotary evaporator, the filtrate from the first recrystallization carried out according to example lb) is evaporated. 200 ml of 10% ammonia and then 200 ml of ethyl acetate are then added. The mixture is stirred for a few minutes, after which it is filtered on a glass frit. The organic phase is separated, washed with water, dried over magnesium sulfate and evaporated in a rotary evaporator and then under vacuum. About 9.11 g of an orange-colored oil is obtained.

b) formation of diastereoisomeric salts with (-)- 2, 3- bis-(4- methyl- benzoyloxy) butanedioic acid

In a 500 ml Erlenmeyer flask equipped with a magnetic stirrer and cooler and placed on an oil bath, 9.08 g of the oil obtained in example 2a) dissolved in 65 ml of absolute alcohol is introduced and then a solution of (-)-2,3-bis-(4-methyl-benzoyloxy)-butanoic acid in 65 ml of absolute ethanol. An abundant precipitate is formed even before the addition is finished. The mixture is then gently heated to the reflux temperature, 140 ml of absolute ethanol is added to achieve complete dissolution of the crystals. Some insoluble crystals are removed by filtration, the filtrate is reheated and set aside at ordinary temperature. After crystallization, filter on glass frit and dry under vacuum at 50°C. 11.2 g of white crystals are then obtained.

c) recrystallises in on

The crystals obtained are recrystallized several times from

95% ethanol. After each recrystallization, approximately 0.25 g is taken from which the base is released with the help of ammonia and chloroform before the rotatability is determined. After five recrystallizations, the rotatability of the base is stable and approximately £ aJD = -63.38° (c = 1.39 in MeOH). The salt then has a rotatability of approximately £ a_7D - -89.21° (c = 1 in MeOH).

EXAMPLE 3 (-)-2,3,3a,4,5,6-hexahydro-1H-indolo[3,2,1-de[]naph tyridine-1,5_7 and its methanesulfonate

a) formation of diastereoisomeric salts with the acid

(-)- 2, 3- bis-(4- methyl- benzoyloxy)- butanedioic acid

In an analogous way as in example la) react 34.41 g of oily base in solution in 250 ml of absolute ethanol with 32.78 g of (-)-2,3-bis(4-methyl-benzoyloxy)-butanedioic acid in solution in 250 ml absolute ethanol, in a 2 liter Erlenmeyer flask with magnetic stirring, reflux condenser and oil bath heating. An abundant amount of crystals is formed before the addition of the diacid is finished at ordinary temperature. It is then heated under reflux and 200 ml of absolute ethanol is added to the mixture to obtain a solution. Some insoluble crystals are removed by filtration. The filtrate is reheated and set aside at normal temperature for crystallization, after which it is filtered on a glass frit and dried under vacuum at 50°C. 35.47 g of crystals are then obtained.

b) recrystallization

One proceeds as in example lc). After four recrystallizations, the rotatability of the base is £aJ^-60.5°

(c = 1.15 in MeOH) and for the salt about £aJD= -87.9°

(c = 1 in MeOH).

c) methanesulfonate

Place in a 250 ml round flask with a magnetic stirrer

1.15 g of the enantiomer (oil) in solution in 20 ml of ethyl ether and the equivalent amount, i.e. 0.52 g of the methanesulfonic acid in solution in 6 ml of ethanol, is quickly added. Crystals form and stirring is continued for 1/2 hour before the crystals are collected and dried at 50°C. They are then recrystallized in 19 ml of absolute ethanol. 1.12 g of methanesulfonate is finally obtained which melts at 219-221°C.

Turning ability:

Elemental analysis and analysis RMN and IR confirm the structure of the compound.

d) demonstration of purity

One proceeds as in example ld). The resulting menthyl carbamate gives, by gas chromatography, a curve with a single peak.

The compounds prepared in accordance with the invention were subjected to pharmacological tests to demonstrate their therapeutic use.

Hypobaric hypoxia

Mice of the strain CD1 are kept in an atmosphere poor in oxygen by creating a partial vacuum (190 mm of mercury corresponding to 5.25% oxygen).

The survival time of the animals is determined. This time is increased by means of means which are able to favor tissue oxygenation and especially cerebral oxygenation. The investigated compounds are administered in several doses intraperitoneally for 10 min. before the experiment. The percentage increase in survival time compared to the values obtained in control animals is calculated. The mild reactive dose that increases survival time by 100% (AD^qq) is determined graphically. AD100s ^ t:L1 ^ mg/kg. AD5Qer ^ to ^ ® mQ/^- Q-

Test with global ischemia in mice

The survival time is measured in experimental animals after they have been injected with 0.1 ml of a saturated solution of magnesium chloride in the caudal vein. Cardiac arrest that results produces cerebral ischemia. The "survival time" is the time interval between the injection of magnesium chloride and the last respiratory movement in each mouse considered as the last sign of a function of the central nervous system.

One compares the survival time of animals treated with compounds prepared in accordance with the invention,

administered intraperitoneally for 10 min. before the injection of magnesium chloride, and the survival time of control animals that have only been given the carrier substance for the active substances. The mice are studied in groups of 10 and the average results for each group allow the recording of a curve and this allows the graphic determination of the effective dose, expressed as mg of active substance per kg body weight, which extends the survival time by 3 sec. (E^D).

Wn increase of the survival time of 3 sec. at the same time provides statistical significance and is reproducible.

The E^D of the compounds prepared in accordance with the invention is 7 to 10 mg/kg.

Pharmacological investigation of compounds prepared in accordance with the invention shows that they have an antianoxia activity that allows their therapeutic use for the treatment of vigilance disorders, in particular to combat behavioral disorders due to cerebral vascular damage and cerebral sclerosis, in geriatrics, as well as the treatment of unconsciousness due to skull injuries, for the treatment of metabolic encephalopathies and for the treatment of depressive conditions.

The compounds and their salts can be used as active ingredients in connection with all usual auxiliary substances for administration, especially oral or parenteral administration.

Daily dose can be from 10 to 100 mg.

Claims (5)

1. Process for the separation of enantiomers of 2, 3, 3a, 4, 5, 6-hexahydro-1H-indolo/3, 2, 1-deJ^/haf tyridine^-1, 57. characterized in that a mixture of enantiomers of formula (I) in the form of a base, is reacted with one of the enantiomers of a chiral acid, one of the two diastereoisomeric salts obtained by fractional crystallization is separated and returned to the base form, and if desired, this is converted into an addition salt of a pharmaceutically acceptable acid. 2. Method as stated in claim 1, characterized in that the chiral acid is 2,3-(4.methyl-benzoyloxy)-butanedioic acid. 3. Method as stated in claim 1 or 2, characterized in that the mixture of enantiomers with formula (I) is the racemate. 4. Method as stated in claim 1 or 2, characterized in that the mixture of enantiomers with formula (I) is made up of mother liquor from a previous separation. 5. Method as stated in claims 1-4, characterized in that the salt formation with the chiral acid and the recrystallization is carried out in ethanol.