DK142849B - Analogous process for preparing 3-methyl-quinoxaline-1,4-dioxide-2-carboxylic acid esters or pharmaceutically acceptable salts thereof with bases. - Google Patents

Description

(11) PRESENTATION 1U28k9 DENMARK <«> Int.CI.» C 07 D 241 / B2 '(21) Application No 1493/72 (22) Filed on 28 March. 1972 (24) Running day Mar 28 1972 (44) The application presented and the petition published on 9 February. 1 961

DIRECTORATE OF

PATENT AND TRADEMARKET SYSTEM (30) Priority requested from it

Apr 20 1971, 135792, US

(71) PFIZER INC., 235 East 42nd Street, New York, N.Y., US.

(72) Inventor: Timothy Henry Cronin, 41 Roxbury Court, Niantic, Connecticut, US: Kenneth Richardson, T Pinecrest Road, North Stonington, Connecti = cut, US.

(74) Plenipotentiary in the proceedings:

Hofman-Bang & Boutard Engineering Company.

(54) Analogous procedure for the preparation of 3-methyl-quinoxaline-1,4-dioxide-2-carboxylic acid esters or pharmaceutically acceptable salts thereof with bases.

The invention relates to an analogous process for the preparation of novel 3-methyl-quinoxaline-1,4-dioxide-2-carboxylic acid esters of the formula or pharmaceutically acceptable salts thereof with bases. These compounds have antibacterial activity against pathogenic microorganisms.

Continued efforts to find novel and useful antibacterial agents have over the years led to the development of a wide variety of organic prototype compounds, including numerous quinoxaline-di-N-oxide compounds. Landquist et al., J. Chem. Soc. 2052 (1956) reported in a study on compounds with enhanced antibacterial and antiprotozoal activity the preparation of several derivatives of 2-methyl and 2,3-di-2,2-dihydro-quinoxaline di-N-oxides in which the methyl groups were converted to such groups such as bromomethyl, acetoxymethyl and hydroxymethyl, including the compound 3-methyl-2-carbethoxyquinoxaline di-N-oxide. However, no utility for these compounds has been demonstrated.

In the disclosure of French drug patent M3717, 2-quinoxaline carboxamide di-N-oxides are disclosed, wherein the carboxamide group may be substituted by alkyl, substituted alkyl, aryl, aralkyl or cycloalkyl. Also indicated, but without indication of structure, are the corresponding 2-quinoxaline carboxylic acid substituted esters. They are reported to be useful in human therapy such as antituberculous, antibacterial, anticancer, antiviral and antiprotozoal agents.

In the descriptions of Belgian patents Nos. 721 724, 721 725, 721 726, 721 727 and 727 728, a number of N-substituted 3-methyl-2-quinoxaline carboxamide di-N-oxide derivatives are disclosed wherein the N-substituent is hydroxyalkyl, lower alkoxyalkyl, alkoxycarbonylalkyl, monoalkylaminoalkyl or dialkylaminoalkyl, as antibacterial agents.

The novel 3-methylquinoxaline-1,4-dioxide-2-carboxylic acid esters produced by the process of the invention have a better antibacterial activity than the compounds known from the aforementioned patents. Furthermore, do the compounds of this invention prove useful? broad-spectrum activity, i.e. activity against both Gram negative and Gram positive bacteria as opposed to the usual Gram negative activity of the known quinoxaline di-N oxides.

Of particular interest because of their antibacterial activity in vivo are compounds of the formula set forth in the preamble of claim 1 wherein R is n-heptyl, ethoxy, 2-carboxyethyl or 3-carboxypropyl.

The process according to the invention is characterized by the characterizing part of the claim.

This process consists in the acylation of pre-prepared 3-methylquinoxaline-1,4-dioxide-2-carboxylic acid hydroxyethyl ester 3 with a monocarboxylic acid halide, with a reactive derivative of a dicarboxylic acid, with an alkyl haloformate or with a chloro or bromoalkanoyl halide. Compounds of the formula set forth in the preamble of claim 1 wherein R is carboxyalkyl is prepared using an activated form of a dicarboxylic acid. This activation may have occurred over the acid halide, mixed anhydride or simple cyclic anhydride, all in the presence of a proton acceptor in a molar amount equivalent to the dicarboxylic acid such as a tertiary amine, e.g. triethylamine.

The condensing agent carbodiimide is also useful in the condensation described above using the dicarboxylic acid and the alcohol.

In practice, the hydroxyethyl ester of 3-methyl-2-quinoxaline carboxylic acid 1,4-dioxide is acylated with at least one equimolar amount plus as much as a $ 100 excess of an activated dicarboxylic acid selected from the above group. This reaction is carried out in an aprotic solvent such as acetone, methylene chloride or chloroform. Reflux temperatures are preferred with reaction times of 2-6 hours. As previously mentioned, a proton acceptor is used in a molar amount equivalent to the dicarboxylic acid. The reaction is then quenched by pouring into water, the mixture is extracted with a water-immiscible solvent and the water layer is acidified with concentrated hydrochloric acid to a pH of about 3. The released product is extracted in chloroform and the organic layer is separated, dried over sodium sulfate. and concentrated in vacuo to dryness. The residue can be further purified by recrystallization from a suitable solvent.

Acylation of the hydroxy moiety with alkyl haloformate leads to the analogs wherein R is alkoxy and is performed using the hydroxyethyl ester and a corresponding haloformate ester in a solvent such as chloroform or methylene chloride, in the presence of a tertiary amine, e.g. pyridine or triethylenamine. Generally, it is advantageous to use as much as a 100% excess of the halogen formate and the tertiary amine. Experimentally, a solution of the hydroxyethyl ester and the tertiary amine, cooled to 0 ° C, is treated with the required halogen formate. After 1-2 hours at ambient temperature, the reaction mixture is treated with a saturated sodium hydrogen carbonate solution and washed against 6N hydrochloric acid. The organic solution containing the product is then dried and evaporated to dryness. The product is usually precipitated in or recrystallized from a suitable solvent.

Similarly, related compounds wherein R is chloro or bromoalkyl are synthesized by contacting the hydroxyethyl ester with a chloro or bromoacyl halide, respectively.

The hydroxyethyl ester is most conveniently prepared from the acyloxy analogs by acid hydrolysis. In practice, a 3-methyl-2-quinoxaline carboxylic acid ethyl ester 1,4-dioxide substituted in the alkyl part of the ester with an alkanoyloxy moiety is added to an aqueous acidic solution, e.g. of sulfuric acid, phosphoric acid or hydrochloric acid.

Generally, the concentration of the acid is about 1 - 12. N with a preferred range of 10 - 12 N. The hydrolysis is produced at temperatures of 0 - 50 ° C with a preferred temperature range of 25 - 35 ° C and a reaction time of from 30 minutes to 3 hours. After completion of the reaction, water is added to the mixture and the pH is adjusted to 5 using an aqueous solution of a base, e.g. sodium hydroxide. The mixture is then extracted several times with a solvent such as chloroform and the organic layer is dried over sodium sulfate and concentrated in vacuo to dryness.

A characteristic feature of those compounds of the formula set forth in the preamble of claim 1 wherein R is carboxyalkyl is their ability to form salts with bases. These compounds are transmitted e.g. in salts by treating the acid with a base in an aqueous or non-aqueous medium. Suitable basic reagents for preparing these salts can vary in nature, and should be understood to include such bases as organic amines, ammonia, alkali metal hydroxides, carbonates, hydrogen carbonates, hydrides and alkoxides as well as alkaline earth metal hydroxides, hydrides, alkoxides and carbonates. Representative of such bases are ammonia, primary amines such as n-propylamine, n-butylamine, aniline, cyclohexylamine, benzylamine, p-toluidine, ethylamine and octylamine, tertiary amines such as diethylaniline, N-methylpyrrolidine, N-methylmorpholine. , 5 diazabicyclo [4.3.3 O] -5-nonene, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium ethoxide, potassium methoxide, magnesium hydroxide, calcium hydride and barium hydroxide.

5 U2849

As previously stated, the quinoxaline di-N-oxides produced by the process of the invention have a high antibacterial activity and are remarkably effective in treating a wide variety of pathogenic microorganisms. Typical compounds of interest in this regard include 3-methyl-2-quinoxaline carboxylic acid 2- (3-carboxypropionoxy) ethyl ester 1,4-dioxide, 3-methyl-2-quinoxylinecarboxylic acid 2- (4-carboxybutyryloxy) - ethyl ester 1,4-dioxide and 3-methyl-2-quinoxaline carboxylic acid 2- (octanoyloxy) ethyl ester 1,4-dioxide.

For topical use, it will often be convenient to combine the selected compound with a pharmaceutically acceptable carrier, such as vegetable or mineral oil or a softening cream. Similarly, they may be dissolved or dispersed in liquid carriers or solvents such as water, alcohols, glycols or mixtures thereof, or other pharmaceutically acceptable inert media, i.e. media which have no adverse effect on the active ingredient. For such purposes, it will generally be acceptable to use concentrations of active ingredients from about 0.01% to about 10% based on the total weight of the mixture.

To determine the activity of an antibiotic in vitro, the sensitivity of the various microorganisms to that antibiotic is determined by the commonly accepted double-dilution technique. Final concentrations of compound per ml ranges from 100 µg in the first glass to 0.19 µg in the tenth glass. The seed material consists of 0.5 ml of a 1 x 10 10 dilution of a standardized culture. The final volume of each glass or dish in the "DisPoso" tray is 1.0 ml. The vials are incubated at 37 ° C for approximately 24 hours. The medium used is Witkin's Synthetic or "Brain Heart Infusion" (BHI). The sensitivity of the test organism (MIC = minimum inhibitory concentration) is accepted as shown by the lack of apparent turbidity.

When used in vivo to control pathogenic microorganisms, the subject compounds may be administered orally or parenterally, e.g. by subcutaneous, intramuscular or intravenous injection, at a dose of from about 1 mg / kg to about 100 mg / kg body weight.

6 142849

The in vivo activity of the compounds is determined by the antibacterial activity against acute infections in mice. The acute experimental infections are produced by intraperitoneal inoculation of a standardized culture suspended in either 5% pig stomach mucin or broth.

When assessing an antibiotic for its effectiveness after a single dose, the dose is usually administered half an hour after inoculation of the mouse with the lethal concentration of organisms.

With this type of treatment schedule, surviving mice are usually kept for four days after treatment, and the percentage of live mice is calculated.

Using the above described method of determining in vivo activity, the following compounds were tested orally against Escherichia coli at 200 and 50 mg / kg: 0

^ Jl / CO9-CH5CHp0? C-R

CQC

o D

RE, coli 200 £ 0 -CH2C1 100 100 -0CH2CH (CH3) 2 90 80 - (CH2) 3CH3 100 60 - (CH2) 6Ck3 100 50 - (CH2) 8CH3 100 70 - (CH2) 2CO2H 100 80 - (CH2) 3C02H 90 50 7 142849

By comparison, activity values for some compounds known from the aforementioned Belgian Patent Specification 721 724 are disclosed and the compound 3 is also known from the aforementioned French pharmaceutical patent M3717:

0 D

Compound E. coll_R_R * Dose% survivor 1. H - (CH2) 3OCH3 12.5 0 50 0 2. H - (CH2) 20CH3 12.5 20 50 50 3. CH3 CH3 50 40 100 50 200 60

The process according to the invention is illustrated in more detail by the following examples.

Example 1 3-Methyl-2-quinoxaline carboxylic acid 2- (acetyloxy) ethyl ester 1,4-dioxide

To a solution of 251.6 g (1.85 mole) of benzofuroxane and 348 g (1.85 mole) of 2-acetoxyethyl-acetoacetate in 75o ml of dimethylformamide at 50-65 ° C is added 370 ml of an M solution of sodium ethoxide in ethanol. . The reaction mixture is stirred at 50 ° C for 4 hours, then cooled, concentrated to half volume and filtered. The resulting crude product is dissolved in chloroform and the chloroform solution is alternately washed with water, brine and water. The organic layer is separated, dried over anhydrous sodium sulfate and concentrated in vacuo to dryness. The residue is triturated with ether, filtered and dried to give 179 g of the above product, m.p. 131-133 ° C during decomposition.

0 142849

ISLAND

Analysis calculated for C C forH Og OgOlL, C 54.9; H, 4.6; N, 9.2 Found: C, 54.7; H, 4.7; N, 9.1.

5-methyl-2-quinoxalincarboxylsvre-2-hvdroxyethylester-l, 4-dioxide

To 100 ml of a 12N hydrochloric acid solution is added 50 g (0.16 mol) of 3-methyl-2-quinoxaline carboxylic acid 2- (acetyloxy) ethyl ester 1,4-dioxide and the resulting reaction mixture is stirred at room temperature for 1 hour. 200 ml of water and 200 ml of chloroform are added to the mixture, which is then cooled and adjusted to pH 5 using a 10? 6 sodium hydroxide solution. The layers are separated and the mixture is further extracted (4 x 100 ml) with chloroform, and the combined chloroform layers are dried over anhydrous sodium sulfate and concentrated to dryness under reduced pressure. The resulting residue is recrystallized from chloroform / hexane to give the pure product as a yellow solid, 33.3 g »m.p. 146-148 ° C.

Analysis calculated for C12 H12 O5 N2: C, 54.5; H, 4.6; N, 10.6.

Found: C, 54.2; H, 4.5; N, 10.7.

3-methyl-2-quinoxaline carboxylic acid 2-C (3-carboxypropionyloxy) ethyl ester-1,4-dioxide

A mixture of 26.4 g (0.1 mol) of 3-methyl-2-quinoxaline carboxylic acid 2-hydroxyethyl ester 1,4-dioxide, 22 g (0.22 mol) of succinic anhydride and 100 ml of triethylamine ill acetone is heated to reflux in 2 hours and then stirred at room temperature for 16 hours. The resulting reaction mixture is poured into water and extracted with chloroform (3 x 250 ml). The aqueous phase is acidified with concentrated hydrochloric acid and the product is extracted with chloroform. The organic layer is separated, dried over sodium sulfate and concentrated to an oil under reduced pressure. The residual product is crystallized from methanol to give 24.7 g, m.p. 165-167 ° C.

Analysis calculated for C 16 H 16 ° 8 N 2: C 52'8 * H k'k '> N 7'7 · found: C 52.9; H, 4.6; N, 7.6.

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By replacing succinic anhydride with glutaric anhydride in the above example, 3-methyl-2-quinoxaline carboxylic acid 2- (4-carboxybutyryloxy) ethyl ester 1,4-dioxide, m.p. 114-117 ° C.

Analysis calculated for C 54.0; H, 4.8; N 7.4.

Found: C, 53.7; H, 4.8; N 7.4.

Using the aforementioned double dilution series technique, the activity in vitro over 200.

EXAMPLE 2 5-Methyl-2-quinoxaline carboxylic acid-2 (octanoyloxy) ethyl ester 1,4-dioxide

To a solution of 26.4 g (0.1 mol) of 3-methyl-2-quinoxaline carboxylic acid-2-hydroxyethyl ester 1,4-dioxide and 30.3 g (0.3 mol) of triethylamine in 200 ml of methylene chloride cooled to 0 ° C 32.5 g (0.2 mole) of octanoyl chloride are added dropwise in 50 ml of the same solvent. After stirring at 0 ° C for one hour, the reaction mixture is allowed to warm to room temperature and then washed with a saturated sodium hydrogencarbonate solution and then with 6N hydrochloric acid. The organic layer is separated, dried over magnesium sulfate and the solvent is evaporated in vacuo to give an amber oil which is crystallized with ether / petroleum ether to give 25.7 g of the above compound, m.p. 62-64 ° C.

By replacing octanoyl chloride with the corresponding acid chloride, the following compounds are similarly prepared: 3-methyl-2-quinoxaline carboxylic acid 2- (valeryloxy) ethyl ester 1,4-dioxide, m.p. 56-60 ° C; 3-methyl-2-quinoxaline carboxylic acid 2- (caproyloxy) ethyl ester 1,4-dioxide, snip. 70-72 ° C; 3-methyl-2-quinoxaline carboxylic acid 2- (enanthyloxy) ethyl ester 1,4-dioxide, m.p. 68-70 ° C; 3-methyl-2-quinoxaline carboxylic acid 2- (capryloxy) ethyl ester 1,4-dioxide, m.p. 60-62 ° C; 3-methyl-2-quinoxaline carboxylic acid 2- (chloroacetoxy) ethyl ester-1,4-dioxide, m.p. 115-117 ° C; and 3-methyl-2-quinoxaline carboxylic acid 2 - [(isobutoxycarbonyl) oxy] ethyl ester 1,4-dioxide, m.p. 72-73 ° C.

EXAMPLE 5 5-Methyl-2-quinoxaline carboxylic acid 2- (3-carboxypropionyloxy) ethyl ester-1,4-dioxide sodium salt

A suspension of 728 mg of 3-methyl-2-quinoxaline carboxylic acid 2- (3-carboxypropionyloxy) ethyl ester 1,4-dioxide in 50 ml of water is treated with one drop of phenolphthalein and then neutralized with 1N sodium hydroxide solution. The cloudy solution is then filtered and evaporated to dryness under reduced pressure to give 665 mg of the desired compound, m.p., 148 ° C.