PT97005B - PREPARATION PROCESS FOR (2-IMIDAZOLIN-2-ILAMINO) TETRAHYDROQUINOXALINS AND PHARMACEUTICAL COMPOSITIONS CONTAINING THEM - Google Patents

Abstract

This invention relates to a process for the preparation of a compound having the formula <IMAGE> in which R1 and R4 are selected, independently of each other, from a group comprising H and alkyl radicals containing 1 to 4 carbon atoms. R2 and R3 are selected independently of each other from a group comprising H, O and alkyl radicals containing 1 to 4 carbon atoms, the 2-imidazolin-2-ylamino group may be in any one of the 5-, 6-, 7- or 3- positions of the quinoxaline nucleus, and each of the R5, R6 and R7 is located in one of the remaining 5-, 6-, 7- or 8- positions in the quinoxaline nucleus and is selected independently of the others from the group comprising Cl, Br, H and alkyl radicals containing 1 to 3 carbon atoms, and their pharmaceutically acceptable acid addition salts. The process comprises the saturation of any unsaturations in the 1-, 2-, 3- or 4-positions of the quinoxaline nucleus of a corresponding (2-imidazoline-2- ylamino)quinoxaline compound, separation of the product produced from the reaction mixture, its recovery and if necessary its formation into a salt. The invention also relates to a process for preparing pharmaceutical compositions containing those compounds. When administered to a mammal the compounds prepared provide desired therapeutic effects such as changes in the rate of transport of fluid in the gastrointestinal tract, reduction in intraocular pressure and an increase in kidney fluid flow.

Description

present invention relates to the process of preparing a compound with the formula

III wherein R ^ and R ^ are independently selected from each other from the group consisting was H and radicals "alkyl containing 1 to 4 carbon atoms, R ₂ ^{and R} 3 ^s ^ ° driven independently from other, among the group consisting of H, 0 and alkyl radicals containing 1 to 4 carbon atoms, the 2-imidazolin-2-ylamino group can be in any of the 5-, 6-, 7- or 8- positions of the quinoxaline core, and each of R _s ., R ₆ and R ₇ is placed in one of the remaining 5-, 6-, 7 · - or 8- positions of the quinoxaline core and is selected, independently of the others, from among the group consisting of Cl, Br, H and alkyl radicals containing 1 to 3 carbon atoms, and their pharmaceutically acceptable acid addition salts., process comprises saturating any irises in the 1-, 2- positions , 3- or 4- of the quinoxaline core of a corresponding (2-imidazolin-2-ylamino) quinoxaline compound, the separation of the product produced, the mixture reaction, its recovery and eventually its formation in a salt., invention refers to the process of preparing

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-2pharmaceutical positions containing those compounds.

The compounds prepared when administered to a mammal, provide desired therapeutic effects such as change in the speed of fluid transport in the testinal gastrin tract, reduction in intraocular pressure and increase in the flow of renal fluid.

J

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-3 DESCRIPTIVE MEMORY

BACKGROUND OF THE INVENTION

The present invention relates to new substituted guinoxaline derivatives. More particularly, the invention relates to derivatives that are useful as therapeutic agents, for example, to effect reduction in intraocular pressure, to increase the flow of renal fluid and to effect a change in the rate of fluid transport in the gastrointestinal tract. .

Various quinoxaline derivatives have been suggested as therapeutic agents. For example, Danielewicz, el. al., U.S. Patent 3,890,319 describe, as regulators of the cardiovascular system, compounds that have the following formula:

H

X

N

H

Y z

R in which the 2-imidazolin-2-ylamino group can be in any of the 5-, 6-, 7- or 8- positions of the quinoxaline nucleus; X, Y and Z can be in any of the remaining 5-, 6-, 7- or 8- positions, and can be selected from hydrogen, twin halo, lower alkyl, lower alkoxy or trifluoromethyl; and R is an optional substituent in one of the 2- or 3- positions of the quinoxaline core and can be hydrogen, lower alkyl or lower alkoxy.

SUMMARY OF THE INVENTION

The new compounds of the present invention are those that have the formula:

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and their pharmaceutically acceptable acid addition salts, in the R 2 and R 2 are selected, independently of each other, from the group consisting of H and alkyl radicals having 1 to 4 carbon atoms, R 2 and R ₃ are selected, one independently of the other, among the group consisting of H, 0 and alkyl radicals with 1 to 4 carbon atoms, the group 2-imidazolin-2-ylamino being in any of the 5-,

6-, 7- or 8-, preferably in position 6-, of the quinoxaline core and R _c , R _r and R _n are each located in □ o / of the remaining positions 5-, 6-, 7- or 8 - of the quinoxaline nucleus, and are selected, independently of each other, from the group consisting of Cl, Br, H and alkyl radicals with 1 to 3 carbon atoms.

Particularly useful compounds are those in which R ^ and R ^ are H, R2 ^and R3 are selected, independently of each other, from the group consisting of H and alkyl radicals having 1 to 4 carbon atoms, the group being 2-imidazolin -2-ylamino at the 6- position of the quinoxaline nucleus, R ^ is selected from the group consisting of Cl, Br and alkyl radicals containing 1 to 3 carbon atoms, more preferably Br, and is at the 5- position of the quinoxaline nucleus and R ^ and R ^ are H.

The pharmaceutically acceptable acid addition salts of the compounds of the invention are those that are formed from acids that form non-toxic addition salts containing pharmaceutically acceptable anions, such as the hydrochloride, hydrobromide, hydroiodide, sulfate salts or bisulfate, phosphate or acid phosphate, acetate, maleate, fumarate, oxalate, lactate, tartrate, citrate, gluconate, saccharate and p-toluenesulfate.

The compounds of the present invention provide one or more

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J ·

-5 therapeutic effects, e.g., in mammals. Thus, these compounds are useful in a method for treating a mammal in which one or more of these compounds are administered to a mammal in an amount sufficient to provide the desired therapeutic effect on the mammal. Among the desired therapeutic effects provided by the present compounds include altering the rate of fluid transport in the gastrointestinal tract of a mammal; the reduction or maintenance of intraocular pressure in at least one of the eyes of a mammal; and increasing the flow of renal fluid in at least one of the kidneys of the mammalian mammal.

DETAILED DESCRIPTION OF THE INVENTION

The compounds of the present invention, i.e., 2-imidazolin-2-ylamino-tetrahydroquinoxaline, are as described above. All stereoisomers, tautomers and mixtures thereof that meet the restrictions of one or more formulas of the present compounds are included within the scope of the present invention.

For example, the two tautomers

are within the scope of the present invention.

The present compounds can be prepared in a manner analogous to the processes described in Danielewicz, el. al., U.S. Patent 3,890,319 for the preparation of quinoxaline derivatives. This patent is incorporated herein, in its entirety, for reference. Once a 2-imidazolin-2-ylaminoquinoxaline derivative has been obtained corresponding to the compound described in Danielewicz, et al, U.S. Patent 3 890 319, this 2-imidazolin-2-ylaminoquinoxaline intermediate is hydrogenated to

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-6saturate any unsaturation in positions 1-, quinoxaline core.

2-, 3- and 4- do

Briefly, 2-imidazolin-2-ylaminoquinoxaline intermediates can be prepared by (1) reacting the appropriate aminoquinoxaline with thiophosgen to form the corresponding isothiocyanate; and (2) reacting this isothiocyanate with excess ethylene diamine to form the corresponding beta-aminoethyl-thio-ureidoquinoxaline, which is then cyclized to the corresponding intermediate. Alternatively, these intermediates can be prepared by (1) reacting the corresponding aminoquinoxaline with benzoyl isothiocyanate to form the corresponding N-benzoyl-thio-ureido compound, followed by hydrolysis in the corresponding thio-ureide compound, or reaction of the aminoquinoxaline with thiocyanate of ammonium to form the thio-urea compound directly; (2) methylation to form the S-methylated derivative of the thio-ureido compound; and (3) reaction with ethylenediamine to form the intermediate.

intermediate 2-imidazolin-2-ylaminoquinoxaline is then reacted to saturate any unsaturation in the positions

1-, 2-, 3- and 4- of the quinoxaline core. For compounds in which R ^, R2, Rg and R ^ are all Η, the intermediate can be hydrogenated. This hydrogenation occurs, preferably with the intermediate dissolved in a liquid, e.g., a lower alcohol such as methanol, ethanol or the like. Preferably, an effective catalyst to promote hydrogenation is present. Examples of such catalysts include platinum group metals, in particular platinum, compounds of platinum group metals, such as platinum oxide, and mixtures thereof. The hydrogen, e.g., free molecular hydrogen, is present in an amount sufficient at least to provide the desired saturation, preferably in an amount which is in excess of that which is necessary to provide the desired saturation of the intermediate. The temperature and pressure at which the hydrogenation occurs are preferably selected to keep the intermediate and the final product substantially in the liquid phase. Temperatures in the range of about 10 ° C to about 100 ° C and the portions in the range of about 56.6 kPa (0.5 atmosphere) at about

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565 kPa (5 atmosphere) often provides acceptable results. These conditions are maintained for a time sufficient to provide the appropriate hydrogenation reaction. This time period is often in the range of about 1 minute to about 2 hours. The final 2-imide zolin-2-ylamino-tetrahydroquinoxaline is separated and recovered from the hydrogenation mixture e.g., using conventional techniques.

For compounds in which R ^, R2, R ^ and R ^ are all H and for compounds in which R ^ and R ^ are H and and / or R ^ are alkyl, the intermediate can be reacted with a reducing agent , hydride, suitable. This reaction preferably occurs with the intermediate and hydride reducing agent dissolved in a liquid. Any suitable hydride reducing agent can be employed. Examples of suitable hydride reducing agents include NaBH4, NaCNBH4, LiAlH4 and the like. The amount of reducing agent, hydride, used must be sufficient to saturate all unsaturation present in the positions

1-, 2-, 3- and 4- of the intermediate. An excess of hydride reducing agent may be employed, as long as it does not result in deterioration of the final quinoxaline product. The liquid employed should be such that it acts as an effective solvent for the hydride intermediate and reducing agent, and can also act to facilitate, eg, activate, the reaction between the intermediate and hydride reducing agent. hydride. Examples of useful liquids include acetic acid, trifluoroacetic acid, tetrahydrofuran, diethyl ether and the like. The liquid employed is preferably selected so as to avoid the reactivity of excess hydride reducing agent. For example, when LiAlH2 is used as a hydride reducing agent, the liquid is preferably tetrahydrofuran, diethyl ether and the like. One or more co-solvents, e.g., lower alcohols, can also be used. The temperature and pressures at which the reaction takes place are preferably selected to keep the intermediate and the final product in the liquid phase. Temperatures in the range of 0 ° C to about 50 ° C and pressures in the range of about 56.5 kPa (0.5 atmosphere) to about 203 kPa (2 atmosphere) often produce acceptable results.

The reaction time is chosen to allow the reaction to 72 233

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occur, and are often in the range of about a minute to about an hour. 2-Imidazolin-2-ylamino-tetraquinoxaline is separated from the reaction mixture and recovered, e.g., using conventional techniques, such as evaporation, deactivation of excess hydride reducing agent, extraction and chromatographic separation.

For compounds in which R1 and / or R4 are alkyl, the intermediate (having no substituents corresponding to R4 and R4) can be reacted with a hydride reducing agent in the presence of a selected aldehyde or aldehydes. The aldehyde or aldehydes used are selected based on the desired group or groups R nos and / or R ^. For example, if R ^ and / or R ^ are methyl, formaldehyde is used, if R ^ and / or R ^ are ethyl, acetaldehyde, etc. is used. The reaction conditions used are similar to those described in the immediately preceding paragraph, with the exception that the reaction time is often in the range of 1 hour to about 24 hours. The amount of aldehyde used can vary depending on the desired final compound. A mixture of final compounds, ie, a compound in which both R ₁ and R 4, are alkyl mixed with compounds in which only one of R ₄ and R 4 is alkyl, can be produced by the reaction. One or more tetrahydroquinoxaline of the present invention, eg, using conventional techniques can be separated and recovered from this mixture.

The present 2-imidazolin-2-ylamino-tetrahydroquinoxaline are useful for providing one or more therapeutic effects in a mammal. Among the desired therapeutic effects are a change, preferably a decrease in the rate of fluid transport in a mammal's gastrointestinal tract, a reduction or maintenance of intraocular pressure in at least one of a mammal's eyes and an increase in the flow of the mammal. renal fluid in at least one of a mammal's kidneys. Thus, for example, the present composition can be effective as an anti-diarrhea agent, as medication for use in the treatment or control of glaucoma and / or medication for use in the treatment or control of kidney disease. An important feature of many of the present compounds is that the desired therapeutic effect is achieved with reduced side effects, in particular with reduced effects on blood pressure.

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-9nea of a mammal to which the present compound is administered.

Any methods of administering the present compound, or compounds, to the mammal to be treated can be used. The preferred particular method of administration is preferably one that allows the present compound or compounds to have the desired therapeutic effect in an effective manner, e.g., low concentration of the medication and low incidence of side effects. In many applications, the present compound or compounds are administered to a mammal in a manner substantially similar to that used to administer alpha agonists, in particular alpha 2 agonists, to obtain the same, or similar, therapeutic effect.

The present compound or compounds can be included in a medication composition in conjunction with one or more other components to provide a medication composition that can be administered effectively. The other components, e.g., carriers, anti-oxidants, bulking agents and the like, can be chosen from materials that are conventional and well known in the art, e.g., because they are included in medication compositions with alpha 2 agonists.

The present compounds are often administered to the mammalian animal's eye to reduce or maintain intraocular pressure in the form of a mixture with an ophthalmically acceptable carrier. Any carrier, e.g., conventional, ophthalmically acceptable, can be employed. Such a carrier is ophthalmically acceptable if it has, substantially, no harmful, permanent or long-term effect on the eye to which it is administered. Examples of ophthalmically acceptable carriers include water, in particular distilled water, saline and similar aqueous media. The present compounds are preferably administered to the eye as a liquid mixture with the carrier. The compounds are most preferably soluble in the carrier so that the compounds are administered to the eye in the form of a solution. When an ophthalmically acceptable carrier is employed, it is preferable that the mixture contains one or more of the present compounds in an amount in the range of about 0, 0001% to about 1%, more preferably from about 0.05% to about 0.5%,

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£ 3 ^

C- ⁴

P / v.

Any method of administering the drug directly to the eye of a mammal can be employed to provide the compound or compounds to the eye to be treated. The term direct administration is intended to exclude general, systemic modes of administration, e.g., direct injection into the patient's blood vessels, oral administration and the like, which result in the compound becoming available systemically. The primary effect on the mammal resulting from direct administration of the present compound or compounds to a mammal's eye is preferably a reduction in intraocular pressure. More preferably, the present compound or compounds are applied topically to the eye or are injected directly into the eye. Particularly useful results are obtained when the compound or compounds are applied topically to the eye.

Topical ophthalmic preparations, for example drops, gels or eye creams are preferred because of the ease of application / ease of dose distribution and less systemic effects. secondary themes. An example of topical ophthalmic formulation is shown in Table I. The abbreviation q.b. means a quantity sufficient to achieve the result or make up the volume.

TABLE I

Ingredient (2-Imidazolin-2-ylamino) tetrahydroquinoxaline

Preservative

Carrier

Buffer Tonicity Adjuster

Purified water anti-oxidant pH adjuster

Quantity (% w / v) about 0.0001 to about 1.0

0-0.10

0-40

1-10

0.01-10

q.b. pH 4.5-7.5 as needed for 100% / Ζ. Ζ. _> «J í .....

/ if ¹ <-? *

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-11 Various preservatives can be used in the ophthalmic preparation described in Table I above. Preferred preservatives include, but are not limited to, benzalkonium chloride, chlorobutanol, thimerosal, phenylmercuric acetate and phenylmercuric nitrate. Similarly, several preferred carriers can be used in such ophthalmic preparations. These carriers may include, but are not limited to, poly (vinyl alcohol), povidone, hydroxypropylmethylcellulose, polyoxamers, carboxymethylcellulose and purified water.

Tonicity adjusters can be used when necessary or convenient. They include, but are not limited to, salts, particularly sodium chloride, potassium chloride, mannitol and glycerin or any other suitable, ophthalmically acceptable tonicity adjusters.

Various buffers and means for pH adjustment can be used as long as the resulting preparation is ophthalmically acceptable. Accordingly, buffers include, but are not limited to, acetate buffers, citrate buffers, phosphate buffers and borate buffers. The acids or bases can be used to adjust the pH of these formulations as necessary.

Similarly, ophthalmically acceptable antioxidants include, but are not limited to, sodium metabisulfite, sodium thiosulfate, acetylcysteine, butyl hydroxyanisole and butylated hydroxytoluene.

Other excipient components that can be included in the example ophthalmic preparation in Table I can be chelating agents which can be added as necessary. The preferred chelating agent is disodium edetate, although other chelating agents may be used instead of or in conjunction with it.

The following non-limiting examples illustrate certain aspects of the invention.

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Preparation of 5-bromo-6- (2-imidazolin-2-ylamino) -1,2,3,4-tetrahydroquinoxaline

1,2,4-triaminobenzene dihydrochloride

600 mg of 10% by weight palladium catalyst on carbon was added to a suspension of 4-nitrophenylenediamine (Aldrich, 10 g, 65.3 ml) in absolute ethanol. The container with the suspension was evacuated and filled with hydrogen three times, and the suspension was hydrogenated at 124 kPa (18 psi) until the hydrogen absorption was finished. The reaction was slightly exothermic and only a hydrogen refill was needed. The resulting light yellow solution, which darkens rapidly in contact with air, was filtered and concentrated to about 150 ml. Concentrated hydrochloric acid (12 ml) was added and the solid formed was filtered off. 12 g of a purple solid (93% yield) was obtained after drying in vacuo overnight, m.p. 224-5 ° C. This solid was determined to be 1,2,4-triaminobenzene dihydrochloride, using various analytical procedures.

6-aminoquinoxaline

Glyoxal adduct and sodium bisulfite (Aldrich, 14.3 g, 50 mmoi) were added in small portions to a 1,2,4-triaminobenzene dihydrochloride solution (9.8 g, 50 mmoi) in 200 ml of 10% sodium carbonate in water. The reaction mixture was heated to 100 ° C for two hours and then cooled to 0 ° C. The crystals formed were filtered and dried in vacuo to obtain a crude yield of 7.06 g (97% yield) of brown crystals. Recrystallization from benzene produced 6.32 g (87% yield) of yellow crystals, mp 157-8 ° C. These yellow crystals were determined to be 6-aminoquinoxaline using various analytical procedures.

6-Amino-5-bromoquinoxaline hydrobromide

6-Aminoquinoxaline (2.08 g, 14.4 ml) was dissolved in 11.5 mml of glacial acetic acid. The solution in water was cooled en72 233

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-13 while adding a solution of bromine (0.74 ml, 2.3 g, 14.4 mmol) in 1.5 ml of glacial acetic acid slowly over 15 minutes. After stirring for an additional 30 minutes, the orange-red solid formed was filtered off and washed thoroughly with dry ether. The solid was dried in vacuo overnight to obtain 4.44 g of crude product (100% yield). The 6-amino-5-bromoquinoxaline hydrobromide compound had no defined melting point. A phase change (from fine powder to red crystals) was noted at about 220 ° C. Decomposition was observed at about 245 ° C. It was used directly in the next step.

6-amino-5-bromoquinoxaline

The crude 6-amino-5-bromoquinoxaline from the previous step was dissolved in water and the saturated sodium bisulfite solution was added until a negative test of the solution with starch-iodide paper was obtained. The solution was then basified with 2 N sodium hydroxide and carefully extracted with ethyl acetate. The organic extract was dried over magnesium sulfate and concentrated under reduced pressure to obtain the free base. The crude product was recrystallized from boiling benzene to obtain yellow crystals, mp 155-6 ° C. The crystals were determined to be 6-amino-5-bromoquinoxaline using various analytical procedures. The yield was 82%.

5-bromo-6-isothiocyanatoguinoxaline

The crude hydrobromide previously obtained (4.27 g, 14.0 mmol) was dissolved in 60 ml of water and thiophosgene (Aldrich, 1.28 ml, 16.8 mmol) was added in small portions with vigorous stirring. . The red color of the solution disappeared after two hours. The formed solid was filtered off and washed thoroughly with water. After drying in vacuo at 25 ° C, 3.38 g (90% yield) of red-brick crystals were obtained, mp 157-8 ° C. A portion of this material was purified by column chromatography to obtain white crystals, mp 157-8 ° C. These crystals were found to be 5-bromo-6-isothiocyanatoquinoxaline using various analytical procedures.

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-145-bromo-6- (N- (2-aminoethyl) thio-ureido) quinoxaline

A solution of the isothiocyanate (3.25 g, 12.2 mmol) in 145 ml of benzene was added to a solution of ethylenediamine (Aldrich,

5.43 g, 90.0 mmol) in 18 ml of benzene at 25 ° C for 2 hours. After stirring for another 30 minutes, the supernatant was discarded. The oil which was left under stirring with dry ether was washed three times and used directly in the next step.

A portion of this product was further purified by column chromatography (SiC ^, CHClg) for characterization. A white solid was recovered which decomposed at 175 ° C with release of gases (in puffs). This white solution was found to be 5-bromo-6- (N- (2-aminoethyl) thio- ureido) quinoxaline.

5-bromo-6- (2-imidazolin-2-ylamino) quinoxaline

The previous crude product was dissolved in 100 ml of dry methanol and the brown solution was refluxed for 19 hours until no hydrogen gas sulphide was released. The mixture was cooled to room temperature and concentrated to about 50 ml. The yellow solid was filtered off and dried in vacuo; weight 2.52 g (70% yield), mp 242-4 ° C.

As the crude product was insoluble in most organic solvents, the initial purification was achieved by acid-base extraction procedures. 23 g of crude product was dissolved in 100 ml of 0.5 N hydrochloric acid. The turbid yellow solution was filtered to obtain a clear orange-yellow solution which was extracted with ethyl acetate (2 x 10 ml). The aqueous phase was cooled to 0 ° C and then basified with 6 N sodium hydroxide, keeping the temperature of the solution below 15 ° C at all times. The yellow solid that precipitated was washed thoroughly with water until the washings were neutral on pH test paper. The solid was dried in vacuo overnight to obtain 1.97 g of yellow solid, m.p. 249-50 ° C. The recovery was around 88%.

Further purification was achieved by recrystallization as described below. The partially purified product, an16761 (AP) -Portugal

-is- y λ / ¹ / * 'ϊ # ¹ 1, &

later, it was dissolved in Ν, Ν-dimethylformamide (about 17 ml / g) at 100 ° C with vigorous stirring. The solution was filtered hot and allowed to cool overnight. Bright yellow crystals were collected by filtration, mp 252-3 ° C. The recovery was 65-77%. The bright yellow solid was determined to be 5-bromo-6- (2-imidazolin-2-ylamino) quinoxaline, using various analytical procedures.

5-bromo-6- (2-imidazolin-2-ylamino) -1,2,3,4-tetrahydroquinoxaline

A thick-walled Parr hydrogenation flask was charged with 5-bromo-6- (2-imidazolin-2-ylamino) quinoxaline (950 mg, 3.23 mmol), platinum oxide (95 mg) and 20 ml of methanol . The contents of the flask were contacted with hydrogen at 103 kPa (15 psi) for 15 minutes. The resulting solution was filtered through acid-washed silicon dioxide, followed by evaporation of the solvent. The resulting leather-colored solid was chromatographed (SiC ^; CHCl ^ / CH ^ OH 80/20 saturated with NH ^ (g)) to obtain 820 mg (86% yield) of an off-white solid, mp 218 -220 ° C. This off-white solid was determined to be 5-bromo-6- (2-imidazolin-2-ylamino) -1,2,3,4-tetrahydroquinoxaline using various analytical procedures.

EXAMPLE 2

Preparation of (+) 2-methyl-5-bromo-6- (2-imidazolin-2-ylamino) -1,2,3,4-tetrahydroquinoxaline

2-methyl-6-nitroquinoxaline

A solution of pyruvic aldehyde (Aldrich, 40% 40% solution in 10%, 5 '65.3 mmol) was added dropwise to a solution of 4-nitro-1,2-phenylenediamine (Aldrich , 10 g, 65.3 mmol) in 50 ml of 10%. The reaction mixture was heated to 80 ° C for four hours. The reaction mixture was cooled to room temperature, diluted with and extracted with CHCl ₃ · The organic extracts were dried over MgSO ₄ and evaporated to obtain 10.7 g (87% yield) as a ti72 red solid 233

16761 (AP) -Portugal ¹⁶ “..... chaff. Using various analytical procedures, this solid was determined to be 2-methyl-6-nitroquinoxaline.

2-methyl-6-aminoquinoxaline

A thick-walled Parr hydrogenation flask was charged with 2-methyl-6-nitroquinoxaline (10.0 g, 52.9) and CH2 OH (200 ml). The flask was flooded with a stream of nitrogen and 10% by weight palladium on charcoal (500 mg) was added. The flask was pressurized with H ₂ at 345 kPa (50 psi) and this pressure was maintained for three hours. The reaction mixture was filtered through acid-washed silicon dioxide and concentrated in vacuo to obtain a leather-colored solid. The crude material underwent chromatography (SiCC / CH ^OH 95/5 saturated with NH ^ (g)) and was recrystallized from benzene to produce 7.4 g (88% yield) of a leather-colored solid. Using various analytical procedures this solid leather color was found to be 2-methyl-6-aminoquinoxaline.

2-methyl-5-bromo-6- (2-imidazolin-2-ylamino) quinoxaline

The title compound (m.p. 260 ° C) was prepared by a series of reaction steps analogous to the steps described in example 1, starting with 2-methyl-6-aminoquinoxaline instead of 6-aminoquinoxaline.

(t) 2-methyl-5-bromo-6- (2-imidazolin-2-ylamino) -1,2,3,4-tetrahydroquinoxaline

A solution of 2-methyl-5-bromo-6- (2-imidazolin-2-ylamino) quinoxaline was cooled to 10 ° C and treated carefully with NaBH4 (5.0 mg, 0.132 mmol). The reaction mixture was stirred for 15 minutes, before removing the solvent in vacuo. The residue was dissolved in H ₂ O, treated with solid NaOH to pH 13 and extracted with CHCl 4. The combined organic extracts were dried over MgSO4 and concentrated in vacuo to obtain a yellow oil. The crude material was chromatographed (SiO ₂ , CHCl ₃ / / CH ₃ OH 80/20, saturated with NH 4 (g)) to obtain 21.8 mg (a 53% yield) of a leather-colored solid, mp 203 -205 ° C. Using several analytical procedures, it was determined that this solid

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-17 leather color was (+) 2-methyl-5-bromo- (2-imidazolin-2-ylamino) -1,2,3,4-tetrahydroquinoxaline.

EXAMPLE 3

Preparation of (+) - 3-methyl-5-bromo-6- (2-imidazolin-2-ylamino) -1,2,3,4-tetrahydroquinoxaline

3-methyl-6-aminoquinoxaline

Pyruvic aldehyde (Aldrich, 892 mg, 4.95 mmol, 1% to 40% solution) was added dropwise to a stirred solution of 1,2,4-triaminobenzene hydrochloride (1.0 g , 4.95 mmol) dissolved in 10% aqueous 200200 ((15 ml). The mixture was heated at 100 ° C for two hours before cooling to room temperature. The mixture was extracted with CHCl2. The combined organic extracts were dried over MgSO4 and concentrated in vacuo to obtain a brown solid. The crude product was chromatographed (SiCC, CHCl ^ / CH ^OH 95/5 saturated with NH ^ (g)) to obtain 616 mg (75% yield) of a yellow crystalline solid. An analytical sample was prepared by recrystallization from benzene, mp 170-173 ° C. Using various analytical procedures, the solid was determined to be 3-methyl-6-aminoquinoxaline.

(+) 3-methyl-5-bromo-6- (2-imidazolin-2-ylamino) -1,2,3,4-tetrahydroquinoxaline

The title compound (mp 250-251 ° C) was prepared through a series of reaction steps as described above in Example 2, starting with 3-methyl-6-aminoquinoxaline in place of 2-methyl-6-aminoquinoxaline .

EXAMPLE 4

Preparation of 5-bromo-6- (2-imidazolin-2-ylamino) -1,4-dimethyl-1,2,3,4-tetrahydroquinoxaline, 5-bromo-6- (2-imidazolin-2-ylamino ) -1-methyl-1,2,3,4-tetrahydroquinoxaline and 5-bromo-6- (2-imidazolin-2-ylamino) -4-methyl-1,2,3,4-tetrahydroquinoxaline.

5-bromo-6- (2-imidazolin-2-ylamino) quinoxaline (291 mg, 1 mmol) was suspended in CH ^OH (2 ml) and treated with acetic acid 233

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gacial co (1 ml). The mixture was treated with NaCNBH4 (252 mg, 4 mmol) and paraformaldehyde (450 mg, 5 mmol) and stirred at room temperature for 4-8 hours. The mixture was quenched with 1 0 (5 ml), basified with solid NaOH (3 g) to pH> 12 and extracted with CHCl 2. The CHClg extracts are dried over MgSO ^, concentrated in vacuo and chromatographed (SiC ^, CHCl ^ / CH ^OH 80/20 saturated with NH ^ (g)) to obtain the title compounds, individually. Each of these title compounds is tested and has been found to have one or more of the useful therapeutic effects that known alpha 2 agonists exhibit.

EXAMPLE 5

Preparation of 5-bromo-6- (2-imidazolin-2-ylamino) -1,4-diethyl-1,2,3,4-tetrahydroquinoxaline, 5-bromo-6- (2-imidazolin-2-ylamino ) -1-ethyl-1,2,3,4-tetrahydroquinoxaline and 5-bromo-6- (2-imidazolin-2-ylamino) -4-ethyl-1,2,3,4-tetrahydroquinoxaline.

The individual title compounds are prepared using the procedure illustrated in Example 4, with the exception that acetaldehyde. do replaces paraformaldehyde (220 mg, 5 mmol) and the reaction time is 6-12 hours instead of 4-8 hours. Each of these title compounds is tested and found to have one or more of the useful therapeutic effects that known alpha 2 agonists exhibit.

EXAMPLES 6 to 8

The three (3) quinoxaline derivatives produced according to Examples 1 to 3 were tested to determine the effect, if any, of these compounds on intraocular pressure.

Each of these materials was dissolved in distilled water at a concentration of 0.1% (w / v). Each of these solutions was administered topically and unilaterally to an un-anesthetized white New Zealand rabbit's eye, in a single 50 microliter tube. The contralateral eye received an equal volume of saline before determining intraocular pressure after administration of the mixture. Also, approximately 10 microliters of proparacaine (topical anesthetic) 0.5% (w / v) were applied to the corneas of each rabbit before

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determination of intraocular pressure. As a control test, six (6) other white rabbits from New Zealand, virgin to drugs, not anesthetized, were treated and tested, as described above, with the exception that no solutions administered to the eyes were included in the solutions. derived from tetrahydroquinoxaline.

The intraocular pressure in both eyes of each rabbit was determined before and after the solutions had been administered. These intraocular pressure measurements were made in a conventional manner using conventional equipment.

The results of these IOP determinations were as follows:

Active Material Example

Difference in

Intraocular pressure, percentage

I — I

N.S

-15.1 + 3.3

Initial effect Maximum effect on Maximum effect on treated eye Untreated eye

-16.0 + 3.3 N.S.

-8.6 + 2.4 (i)

-12.5 + 2.2

N.S.

Control

N.S.

N.S.

N.S.

N.S. means that the effect was not statistically significant.

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-20 These results indicate that all 5-bromo-6- (2-imidazolin-2-ylamino) -1, 2,3,4-tetrahydroquinoxaline (Example 6), (+) 2-methyl-5-bromo- 6- (2-imidazolin-2-ylamino) -1,2,3,4-tetrahydroxyquinoxaline (Example 7) and (+) 3-methyl-5-bromo-6- (2-imidazolin-2- ylamino) -1,2,3,4-tetrahydroquinoxaline (Example 8) are effective in reducing intraocular pressure in the treated eye of the rabbit,

i.e., the eye to which the active material was administered directly. The tetrahydroquinoxaline derivative of Example 6 had an initial effect on the treated eye of increasing intraocular pressure. The tetrahydroquinoxaline derivative of Example 7 also resulted in the reduction of intraocular pressure in the untreated eye of the rabbit.

Examples 9 to 11

The tetrahydroquinoxalins produced in Example 1 to 3 were tested for activity using the following in vitro methods.

Rabbit Deferent Duet; _Alpha 2 Adrenergic Receptors

New Zealand white rabbits (2-3 kg) were killed by CO ₂ inhalation and deferred ducts were removed. The prostatic ends of the deferent ducts (lengths of 2-3 cm) were mounted between platinum ring electrodes in 9 ml of organ bath and bathed in Krebs bicarbonate solution with the following composition (millimolar): NaCl 118.0; KC1 4.7; CaCl ₂ 2.5; MgSO4 1.2; KH ₂ PC> 4 1.2; glucose 11.0; NaHCO25.0; this solution was maintained at 35 ° C and was bubbled with 95% 0 ₂ and 5% CO ₂ . The initial tension of the vas deferens was 0.5 g. The tissues were left to equilibrate for 30 minutes before stimulation started. The duets were then stimulated (0.1 Hz, pulse width from 2ms to 90 mA), using a quad wave stimulator. (WPI A310 Accupulser with stimulus A385). Tissue contractions were recorded isometrically using force-displacement transducers, Grass FT03, and visualized on a Grass Model 7D polygraph. Cumulative concentration-response curves were obtained for the tetrahydroquinoxaline in test with a contact time of 4 minutes at each concentration. The reduction in response height

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-21 was measured and expressed as a percentage of the height of the response before adding tetrahydroquinoxaline. Concentration-response curves were plotted for each of the tetrahydroquinoxalins. From these curves, the effective concentrations necessary for a 50% reduction in response height were obtained, expressed as ΟΕ ^ θ, which are indicated Next,

Rabbit Aorta: Alpha adrenergic receptors 1

Rabbit Saphenous Vein: Alpha 3 Adrenergic Receptors

Specimens of the thoracic aorta and saphenous vein were obtained from albino rabbits that were killed by inhalation of ^A aorta and the saphenous vein were each cut into 3 mm rings. The tissues were placed in a Krebs-Hensleit solution with the following composition (millimolar): NaCl 119; KC1 4.7; MgSO4 1.5; Ki ^ PO ^ 1,2; CaCl2 2.5; NaHCO ^ 25 and glucose 11.0. The solution also contained cacaine (0.1 millimolar) to block neuronal absorption and EDTA (30 micromolar) and ascorbic acid (5 micromolar) to prevent oxidation of the tetrahydroquinoxaline under test. The tissues were suspended in 10 ml of organ bath and the tension was measured using Grass FT03 force-displacement transducers. The resting tension was 1 g and 2 g for the saphenous vein and the aorta, respectively. The solution was aerated with 95% O2 and 5% CC> 2 ^and maintained at 37 ° C. The tissues were allowed to equilibrate for two hours before the stimulation and cumulative addition of the tetrahydroquinoxaline began. Stimulation was performed as for the rabbit's deferent duet, described above. Tissue contractions were measured isomerically as in the rabbit deferent duct assay. Cumulative concentration-response curves were obtained and the CEç-θ values developed in a similar way to those of the assay with the rabbit's deferent duet.

The results of these in vitro tests were as follows:

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Active Material Example

-22 ^EC 50 nanomolar rabbit Aorta

Duet deferen Veia Safe te do bunny in the bunny

(_)

6750 + 116 (n = 3) r ~ y (í)

1060 + 271 (n = 3)

1130 + 207 (n = 8)

1.75 (n = l)

35.3 + 3.9 (n = 5)

21.3 + 3.0 (n = 2)

92 + 19 (n = 6)

581 + 29 (n = 2) n is equal to the number of times that a particular test was performed.

These results indicate that the present tetrahydroquinoxa mines have some activity in relation to all alpha 1, alpha 2 and alpha 3 drainage receptors. However, these materials have a particularly high activity in relation to alpha 2 adrenergic receptors. Thus, the present tetra -hydroquinoxalins are properly classified as an alpha 2 agonist.

EXAMPLE 12

The tetrahydroquinoxaline produced in Example 1 was tested for effects on blood and kidney pressure using the following method.

Young male Sprague-Dawley rats (20-24 weeks old) were used. Under ketamine anesthesia (60 mg / kg body weight, i.m.) And pentobarbital (i.p. until effective), implanted

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medical grade plastic tubes in the abdominal aorta and vena cava through the femoral vessels. In addition, a stainless steel cannula covered with Silastic was sewn into the urinary bladder. After the surgery, the rats were housed individually and allowed free access to food and water until the day of the experiment.

For about 7 to 10 days before surgery and during recovery, the rats were used to restraining cages by placing them in the cage for two to three hours every 2? and 39 days. The cage was designed for renal clearance studies (a Restrainer model G sold by Braintree Scientific, Inc., Braintree, Massachusetts). The animals' habituation to the cage was judged by the stability of blood pressure and the heart rate.

For an experiment, a rat was placed in a restriction cage and the arterial line was connected to a Statham pressure transducer and Beckman Dynograph R61 to follow the mean arterial blood pressure, hereinafter referred to as MAP. The venous line was connected to an infusion pump system for infusion to replace fluid. Tetrahydroquinoxaline was administered intra-duodenally through the cannula. The bladder cannula was extended with a silastic tube to facilitate the collection of urine in previously weighed tubes. Urine volume was measured gravimetrically. Body weight was recorded before and after the experiment.

During the experiments, 0.9% NaCl containing 10% polifructosan (Inutest) and 1% sodium PAH were infused at a flow rate of 20 microliters / minute. A 60-minute equilibration period was followed by two consecutive 30-minute clearance control periods. Then, tetrahydroquinoxin was administered for 90 minutes. Urine collection was resumed 10 minutes after the start of tetrahydroquinoxaline administration.

By this time, the dead space in the bladder cannula (approximately 200 microliters) was complete. Three additional clearance measurements were made. Blood samples (150 microliters) were collected at midpoints of urine collections.

Plasma was separated and saved for analysis and cells were

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-24 resuspended in saline and returned to the animals. The losses of water and sodium were carefully replaced by i.v. by a variable speed infusion pump.

The results of these tests were as follows:

Tetrahydroquinoxaline dose of Example 1, mg / kg body weight

Increase in urine flow microliters / min / / 100 g body weight

Increase in MAP, mm Hg

0.01 0 0 0.03 4 0 0.1 16 0 0.3 24 2.5 1 32 8

The test was performed three times. Results at 0.1 mg / kg body weight and higher dosages represent statistically significant differences (i.e., in an analysis of this conventional data tactic, P is less than 0.05).

These results indicate that the presence of substituted quinoxalins produces relatively large renal effects. In addition, these results show that these renal effects are produced without a correspondingly large effect on blood pressure.

)

EXAMPLE 13

The tetraquinoxaline produced in Example 1 was tested for anti-diarrhea effects and effects on blood pressure, using the following method.

Rats were performed on rats that had not been fasted as follows. Under anesthesia with methohexital (60 mg / kg i.p.), a laparotiflectomy with a 2 cm mid-ventral incision was started. The cecum was lifted from the abdominal cavity and externalized to gauze. The cecal apex was released by color from the avascular area of the mesocecum. Next, a # 1 silk suture bandage is positioned to occlude the cecum and its vas

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culature without compromising the ileo-colonic potency. After the ligature was fixed and the ileo-colonic potency was confirmed, the cecum was resected and the rest of the caecal mucosa was washed, exposed and washed with saline and was cauterized. The intestinal segment was then replaced in the abdominal cavity and the abdominal muscle bundles were closed with interrupted 4/0 chromium-gut sutures. The dermal incision was closed with 9 mm stainless steel wound clamps, which were removed approximately one week after surgery. An arterial line was also implanted in the abdominal aorta and vena cava, through the femoral vessels, in a similar way to that described in example 10. The animals were replaced in their cages immediately after the surgical procedures and allowed free access to water and food. The animals were allowed a recovery period of at least 48 hours before being used in experiments.

The cecectomized rats were placed in individual wire-bottom cages, placed on clean sheets of paper and deprived of food and water for the duration of the test. MAP was followed as described in Example 10, throughout the test. Rats were given an acclimatization period of 2 hours before starting the trial in order to eliminate sporadic episodes of anxiety-induced defecation. During this period the animals were observed regarding the occurrence of feces in the form of pellets; an animal that produced feces other than pellets was disqualified from the study.

Diarrhea was induced with oral administration of 16,16-dimethylprostaglandin E ^ (dmPGE ₂ ) in 3.5% ethanol. Tetrahydroquinoxaline was administered by forced feeding after the onset of diarrhea episodes. The cage papers were removed and examined at 30 minute intervals for dmPGE _2- induced diarrhea. Fecal emission was recorded at each interval and fecal consistency was assigned a numerical scale in each experimental group, as follows: 1 = feces normal in pellets; 2 = stools with soft consistency; 3 = watery stools and / or diarrhea. The fecal emission index (FOI) is defined as the sum of the number of defecation episodes and their graded consistency according to es72 233

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-26 scale within a given observation period.

The results of these tests were as follows:

Tetrahydroquinoxaline dose of Example 1, mg / kg Body weight, p.o.

Percent reduction in FOI versus dmPGE _{2 control}

i

Increase in MAP, mm Hg

0.01 17 0 0.03 60 0 0.10 57 0 0.30 76 0 1.00 98 0 3.00 98 10 10.00 100 25

These results indicate that the tetrahydroquinoxaline produced in Example 1 provided substantial anti-diarrhea effects. Furthermore, these results indicate that the anti-diarrhea effects are produced with none or with a relatively minimal effect on blood pressure.

Although this invention has been described with respect to a number of specific examples, it should be understood that the invention is not limited to them and that it can be practiced in various ways within the scope of the claims that follow.

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Claims (15)

1 - Process of preparing a compound with the formula N N R R in which, R ^ and R ^ are selected, independently of each other, from the group consisting of H and alkyl radicals containing 1 to 4 carbon atoms, R ₂ and R ₃ are selected, independently of each other, from between the group consisting of H, 0 and alkyl radicals containing 1 to 4 carbon atoms, the 2-imidazolin-2-ylamino group can be in any of the 5-, 6-, 7- or 8- positions of the quinoxaline nucleus, and each of Rg, Rg and is placed in one of the remaining 5-, 6-, 7- or 8- positions of the quinoxaline nucleus and is selected, independently from the others, from the group consisting of Cl, Br, H and alkyl radicals containing 1 to 3 carbon atoms, and their pharmaceutically acceptable acid addition salts, characterized in that the appropriate (2-imidazolin-2-ylamino) -quinoxaline compound is reacted in order to saturate any unsaturations in the 1-, 2-, 3- positions and 4 from the quinoxaline core, separate from the reaction mixture the final (2-imidazolin-2-ylamino) -tetrahydroquinoxaline and recover, and eventually form a salt. Process according to claim 1, characterized in that in the prepared compound the group 2-imidazolin-2-ylamino is in position 6 of the quinoxaline nucleus, Rg is in position 5- of the nucleus quinoxaline and is selected from the group that consists of Cl, Br and alkyl radicals containing 1 to 3 carbon atoms and Rg and R.? are both H. Process according to claim 2, characterized in that in the prepared compound each of R ^ is H. Process according to claim 2, characterized in that in the prepared compound R ₂ and Rg are selected, independently 72 233 16761 (AP) -Portugal from among the group consisting of H and ra -28 * fearful of each other, dical methyl. Process according to claim 3, characterized in that in the prepared compound R ₂ and R ₃ are selected, independently of each other, from the group consisting of H and the radical methyl. Process according to claim 4, characterized in that the prepared compound R ₂ and R ₂ are different. Process according to claim 5, characterized in that the prepared compound R ₂ and R ₂ are different. Process according to claim 2, characterized in that in the prepared compound R ^ is Br. Process according to claim 3, characterized in that in the prepared compound R_ is Br. □ Process according to claim 4, characterized in that in the prepared compound R $ is Br. Process according to claim 6, characterized in that in the prepared compound R $ is Br. Process according to claim 1, characterized in that the compound is prepared: r \ HN NH by hydrogenation of the appropriate (2-imidazolin-2-ylamino) -quinoxaline compound, separation of the reaction mixture, and recovery and, possibly, the formation of a salt. Process according to claim 1, characterized in that the compound is prepared: 72 233 16761 (AP) -Portugal CH by reaction of the compound (2-imidazolin-2-ylamino) -quinoxaline with a suitable reducing agent, hydride, suitable, separation, from the reaction mixture, and recovery, and eventually the formation of a salt. Process according to claim 1, characterized in that the compound is prepared: ΓΆ by reacting the compound (2-imidazolin-2-ylamino) -quinoxaline with a suitable reducing agent, hydride, suitable, separating, from the reaction mixture, and recovering and possibly forming a salt. 15 - Process for the preparation of a pharmaceutical composition, characterized in that a compound prepared according to the preceding claims is associated with pharmaceutically acceptable vehicles and / or excipients.