AU707032B2 - Novel 1-ethyl-1,2-dihydro-2-oxo-3-methylamino-quinoxaline derivatives, their use as medicinal products and the pharmaceutical compositions comprising them - Google Patents

Description

Wo 96/26928 1 PCT/FR96/00312 NOVEL 1-ETHYL-1,2-DIHYDRO-2-OXO-3

-METHYLAMINO-

QUINOXALINE DERIVATIVES, THEIR USE AS MEDICINAL PRODUCTS AND THE PHARMACEUTICAL COMPOSITIONS COMPRISING THEM The present invention, developed at the Pierre Fabre Research Center, relates to novel chemical compounds and to their application as medicinal products.

The Applicant has previously described a series of compounds with bronchodilatory activity (Pierre Fabre Medicament patent FR-2,696,456 of 7/10/92).

This previous invention covers compounds of general formula I R1 o Nx N

R,

N 0 R3 in which R1 and R2 represent, independently of each other, hydrogen or a linear or branched C 1

-C

4 alkyl radical, R3 represents a linear or branched C 3

-C

6 alkyl, alkenyl or hydroxyalkyl group.

The present invention relates specifically to the compounds of general formula I for which: R1 represents hydrogen or a methyl group, R2 represents a methyl group, and R3 represents an ethyl group.

In addition, the invention covers the salts of the compounds of general formula I defined above with pharmaceutically acceptable acids.

The compounds of the present invention distinguish themselves from the prior art, and in particular from the compounds of the same chemical family described previously by the Applicant, on the basis of their high solubility in aqueous medium.

Indeed, the compounds of the invention have a 2 water solubility at 25 0 C of greater than or equal to compared with a solubility of less than or equal to 0.1% for the compounds described previously and the products for which R3 methyl. This unexpected property also increases the bioavailability of these products and their duration of action.

The compounds of the present invention are also characterized by the demonstration, in vivo, of antiinflammatory properties on a model of bronchial allergic inflammation induced in Brown Norway rats. The compounds especially reduce the bronchial eosinophilia.

The examples below illustrate the invention without, however, limiting its scope.

The elemental analyses and the infrared and NMR spectra confirm the structure of the products obtained.

EXAMPLE 1: 1-Ethyl-l,2-dihydro-2-oxo-3-methylaminoquinoxaline hydrochloride 1) 3-Ethyl l-ethyl-1, 2 -dihydro-2-oxoquinoxalinecarboxylate.

11.55 g (0.084 mol) of potassium carbonate and 12.6 ml (0.096 mol) of ethyl sulfate are added to a suspension of 18.25 g (0.084 mol) of 3-ethyl 2-hydroxyquinoxalinecarboxylate in 300 ml of acetone and the mixture is refluxed for 1 hour. After evaporation of the solvent under vacuum, the residual mass is extracted with ethyl ether. The inorganic salts are then filtered off and the filtrate is evaporated under vacuum. The brown oil thus obtained is purified on a column of silica.

Elution with a 30/70 ethyl acetate/hexane mixture gives, after evaporation, 12.41 g (60% yield) of compound in the form of off-white crystals.

m.p. 80-81 0

C

TLC: Rf 0.30 (30/70 ethyl acetate/hexane).

2) l-Ethyl-1,2-dihydro-2-oxo-3-quinoxalinecarboxylic acid.

A solution of 13.79 g of the above ester (0.056 mol) in 50 ml of 950 ethanol and 56 ml of 2 N sodium hydroxide (0.112 mol) is stirred for 30 minutes at 3 0 C. After cooling and acidification by addition of N hydrochloric acid solution, the suspension obtained is chilled for one hour. The crystals are then filtered off, washed with water, with ethanol and then dried under vacuum at 50°C. 10.38 g of acid are thus recovered in the form of yellow flakes.

yield, m.p. 182 0

C.

TLC: Rf 0.65 (50/50 methanol/chloroform).

3) l-Ethyl-1,2-dihydro-2-oxo-3-tert-butoxycarbonylaminoquinoxaline.

A solution of 11.40 g (0.05227 mol) of the acid obtained above, 15.1 ml of triethylamine (0.11 mol) and 23.1 ml (0.105 mol) of diphenylphosphoryl azide in 350 ml of tert-butanol is refluxed for 6 hours. After evaporation of the solvent, the residual oil is taken up in sodium bicarbonate solution and extracted with ethyl acetate. The organic phase is washed with water, with brine and then dried over sodium sulfate and concentrated under vacuum. The solid obtained is triturated from ethyl ether, filtered off, washed and dried to give 9.07 g of white crystals (60% yield) melting at 98 0

C.

TLC: Rf 0.43 (30/70 ethyl acetate/hexane).

4) l-Ethyl-1,2-dihydro-2-oxo-3-methylaminoquinoxaline hydrochloride 1.

A solution of 8.68 g (0.03 mol) of the above carbamate in 100 ml of tetrahydrofuran is stirred for 24 hours at room temperature in the presence of 3.4 ml of methyl sulfate, 21 ml of 6 N sodium hydroxide and 684 mg of benzyltriethylammonium chloride.

After evaporation of the solvent, the residue is taken up in water and extracted with ethyl acetate.

After washing with water, drying over sodium sulfate and evaporation under vacuum, the oil recovered (intermediate N-methylcarbamate) is treated with 50 ml of 6 N hydrochloric acid solution for 2 hours at 60 0 C. This solution is then poured onto ice and neutralized by addition of 6 N sodium hydroxide. The solid formed is extracted with ethyl acetate, the solution is dried and an ethanolic solution of hydrogen chloride gas is then 4 added thereto; the precipitate formed is -filtered off, washed with ether and then dried.

6.40 g (yield 89%) of compound are thus recovered in the form of white crystals.

m.p. 171*C.

TLC: Rf 0.35 (30/70 ethyl acetate/hexane).

EXAMPLE 2: 1-Ethyl-1,2-dihydro-2-oxo-3-dimethylaminoquinoxaline hydrochloride, 2.

2.15 g (0.009 mol) of compound in 15 ml of N,N-dimethylacetamide are stirred for one hour at room temperature in the presence of 0.4 g of 60% sodium hydride. 1.54 ml (0.025 mol) of methyl iodide are then added and the mixture is heated at 60°C for 1 hour. After evaporation of the solvent under vacuum, the hydrochloride is obtained as in the above example. 1.96 g of white crystals are isolated (yield m.p. 130- 131°C. TLC: Rf 0.39 (95/05 toluene/ethyl acetate).

SOLUBILITIES

The water solubilities at 25°C of compounds 1 and 2 of the invention are compared in Table I with those of the corresponding compounds 3 to 6 described and claimed previously (FR-A-2,696,456) and 7 described by J.W. Clark-Lewis Chem. Soc. 1957, 42).

5 Table I Compounds R1 R2 R3 Salt Solubility 1 CH 3 H C 2 Hs HC1 5 2 CH 3

CH

3

C

2 Hs HC1 10 3 CH 3 H nC 3

H

7 HC1 0.1 4 CH 3

CH

3 nC 3

H

7 HC1 0.1

CH

3 H nC 4 H, HC1 0.1 6 CH 3

CH

3 nC 4

H

9 HC1 0.1 7 CH3 H CH3 HC1 0.1 BIOLOGICAL EXPERIMENTS 1 Pharmacological study a) in vitro spasmolytic activity on trachea isolated from quinea pig.

The compounds of the invention were subjected to pharmacological tests which showed their value as bronchial spasmolytic agents.

To this end, the compounds were studied as regards their antagonist effect on the contractions induced by histamine, according to the following procedure.

A piece of trachea from a male three-colored guinea pig weighing 400 g on average is cut into hoops and mounted (about 2.5 cm) in an insulated organ tank thermostatically adjusted to 37°C and filled with oxygenated Tyrode's solution. The isometric contractions induced by histamine are recorded by means of a UC2 Gould Statham sensor (Gould Inc. Oxnard, California, USA) or UF1 Palmer Bioscience sensor connected to a potentiometric recorder (Linseiss, Selb, RFA).

At the start of the experiment, the strip of 0 6 trachea is subjected to a tension of 1 g and left at rest for 1 h.

Histamine hydrochloride at a concentration of gg/ml (concentration generally inducing a maximum contraction) is used. The concentration of agent used leads to contractions which reach a maximum after 5 to min and then maintain a steady state. A concentration of the test product is administered for each contraction and the product is left in contact with the trachea for 5 min. Any inhibition obtained after this time (percentage of variation in the amplitude of the contraction) is measured. The trachea is then washed for 15 seconds and left at rest for about 10 min (time required to return to the basal tonus) before inducing a new contraction.

Compound 5, which is insoluble in water, is diluted in 0.178% (final concentration in the bath) of dimethyl sulfoxide (DMSO). This DMSO concentration does not cause any effects as regards the contractions of the mediator studied.

The 50% inhibitory concentrations

(IC.

0 are calculated using an SAS (Statistical Analysis System) program based on Bliss and Cattel (Bliss C.I. and Cattel McK. Biological Assay Ann. Rev. Physiol. 5, 479, 1943).

The results obtained on compounds 1 and 2 of the present invention are reported in comparison with compound 5, representing the series described previously, in Table II.

Table II Compound No. Histamine ICso (Ag/ml) 1 3.8 2 8.8 2.3 7 b) in vivo bronchodilatory activity: test of exposure to a histamine aerosol on conscious guinea Male Dunkin Hartley guinea pigs weighing 300 350 g are placed in a circular glass chamber 8 1 in volume. The guinea pigs are exposed to an aerosol of 1% histamine dihydrochloride generated by a Jouan (Paris) "aerolizer", leading to the formation of dry particles of 1 3 gm delivered by compressed air at an hourly flow rate of 28 ml under a pressure of 1 bar.

The time for the animal to fall onto its flank (preconvulsion time) is measured. At this moment, the animal is removed from the chamber and possible death within 10 min is noted. The maximum exposure time to the aerosol is 3 min.

The animals are treated with the test products intraperitoneally 15 min before the test or orally 1 h before the test. For the oral administration, the products are dissolved in distilled water (soluble products I and II) or are suspended in a mixture of Tween 80 and distilled water (product III). For the intraperitoneal administration, the products are dissolved in 9 O/o NaC1 or are suspended in a mixture of Tween 80 and 9 °/oo NaCl. The control animals receive the appropriate solvent alone under administration conditions identical to those of the treated animals. The volume administered is always 10 ml/kg. Any protective activity of the products is quantified by evaluating the protected animals in comparison with the respective control animals. Whenever this was possible, an EDs, (effective dose in 50% of the animals) was determined (Table III).

8 Table III Compound No. EDso i.p. EDso p.o.

(mg/kg) (mg/kg) p.o./i.p.

1 9.7 8.4 0.9 8.6 21 2.4 The ratios of the EDso values demonstrate an increase in the bioavailability of product 1 which is the subject of the present invention, when administered orally.

A duration of action of about 4 hours for compound 5 and of more than 8 hours for compound 1 is also observed.

c) Test of bronchial allergic inflammation The compounds of the invention were tested on the model of bronchial allergic inflammation induced in Brown Norway rats Tarayre, M. Aliaga, M. Barbara, N. Tisseyre, S. Vieu, J. Tisne-Versailles: Model of bronchial allergic inflammation in Brown Norway rat.

Pharmacological modulation. Int. J. Immunopharm, 1992, 14, 5, 847-855).

This model reproduces in Brown Norway rats the bronchial eosinophilia obtained in atopical asthma patients 24 h after the inhalation of allergen (De Monchy Kauffman Venge Koeter G.H., Jansen Sluiter De Vries L. Am. Rev. Resp.

Dis. 131, 373-376, 1985).

The products are administered intraperitoneally min and 5 h after exposure to the antigen (ovalbumin) aerosol. The number of bronchial eosinophils is determined after collection by bronchoalveolar washing 24 h after exposure to the antigen. Any reduction in the bronchial eosinophils by the test compounds is quantified in comparison with controls receiving only the solvent under the same administration conditions (Table IV).

M

9 Table IV Compound No. Dose Inhibition of the mg/kg (x 2) bronchial eosinophilia 1 5 52 2 5 69 2 Therapeutic applications The compounds of the invention are bronchodilators which may be used for the treatment of diseases such as chronic obstructive bronchopneumopathies, respiratory insufficiency and emphysema.

The compounds of the invention may be used in particular in the treatment of asthma. In recent years, the role of inflammation in the deterioration of the bronchial mucosa has been clearly demonstrated in this pathology. The blood eosinophils which accumulate in the mucosa and the bronchial lumen appear to be the main sources of the mediators which induce this inflammation in asthma (Gleich G.J. The eosinophil and bronchial asthma: current understanding. J. Allergy Clin. Immunol.

422-436, 1990).

The addition of antiinflammatory properties to the bronchodilatory properties of the compounds claimed may allow their use as chronic treatment in asthma.

The pharmaceutical compositions contain as active principle at least one compound defined according to the invention, combined with an inert pharmaceutical support or another pharmaceutically acceptable vehicle or any other suitable excipient. The pharmaceutical compositions may be in a form which is suitable for oral, rectal, parenteral or local administration, for example in the form of wafer capsules, tablets, granules, gelatin capsules or drinkable suspensions, syrups or liquid solutions, aerosols or sprayable solutions, and may contain suitable excipients.

The pharmaceutical compositions may contain as 10 active principle at least one compound defined according to either of Claims 1 and 2, combined with another active principle.

The daily dosage may range from 50 to 1000 mg.

Claims (6)

1. l-Ethyl-l,2-dihydro-2-oxo-3-methylaminoquinoxaline derivatives of general formula I R I C N N CH 3 C

2 H in which RI represents hydrogen or a methyl group, and the salts thereof with pharmaceutically acceptable acids. 10 2. Derivates of general formula I according to claim 1, characterized in that they are chosen from: 1-ethyl-l,2-dihydro-2-oxo-3-methylaminoquinoxaline hydrochloride; and 1-ethyl-1,2-dihydro-2-oxo-3-dimethylaminoquinoxaline hydrochloride.

3. A method of treating chronic obstructive bronchopneumopathies, in particular asthma, respiratory insufficiency and emphysema, in a patient in need of such treatment, which method comprises the administration of a pharmacologically effective amount of a compound according to claim 1 or claim 2.

4. Pharmaceutical compositions, characterized in that they contain as active principle at least one compound defined according to either of claims 1 and 2, combined with an inert pharmaceutical support or another pharmaceutically acceptable vehicle or any other suitable excipient.

BMH:SH:##26278.RS1 4 May 1999 Pharmaceutical compositions, characterized in that they contain as active principle at least one compound defined according to either of claims 1 and 2, combined with another active principle.

6. l-Ethyl-l, 2 -dihydro-2-oxo-3-methylaminoquinoxaline derivatives substantially as hereinbefore described with reference to the non-comparative examples. DATED: 4 May 1999 W.. CARTER SMITH BEADLE Patent Attorneys for the Applicants: PIERRE FABRE MEDICAMENT cllBMH:SH:##26278.RS1 4 May 1999