United States Patent (19)
`Gluchowski
`
`11
`45
`
`Patent Number:
`Date of Patent:
`
`5,021,416
`Jun. 4, 1991
`
`
`
`54 METHOD FOR USING
`(2-MDAZOLN-2-YLAMNO)
`QUINOXALINES TO REDUCE OR
`MANTAN INTRAOCULAR PRESSURE
`75 Inventor: Charles Gluchowski, Mission Viejo,
`Calif.
`73) Assignee: Allergan, Inc., Irvine, Calif.
`(21) Appl. No.: 429,835
`(22
`Filed:
`Oct. 31, 1989
`51) int. C. .............................................. A6 K 31/50
`52 U.S. C. .................................................... 514/249
`58) Field of Search ......................................... 514/249
`(56)
`References Cited
`U.S. PATENT DOCUMENTS
`3,890,319 6/1975 Danielewicz ....................... 544/284
`FOREIGN PATENT DOCUMENTS
`2538620 8/1975 Fed. Rep. of Germany .
`OTHER PUBLICATIONS
`Burke et al. Current Eye Research; Sep. 5 (9): 665-76
`(1986).
`Mittag. Annals of Ophthalmology 1983; 15(3): 201-202.
`Renal Effects of Selective Alpha-1 and Alpha-2 Adre
`noceptor Agonists in Conscious, Normotensive Rats;
`Miklos Gellai & Robert R. Ruffolo, Jr.
`Selective Alpha-2. Adrenoceptor Agonists Alter Fluid
`and Electrolyte Transport in Mammalian Small Intes
`tine; Joseph D. Fondacaro, David Kolpak & Gerald P.
`McCafferty.
`Ocular Effects of a Relatively Selective Alpha-2 Ago
`
`nist (UK-14, 304-18) in Cats, Rabbits and Monkeys; J.
`A. Burke and D. E. Potter.
`Alpha-2 Adrenergic Modulation of Norepinephrine
`Secretion in the Perfused Rabbit Iris-Ciliary Body;
`James E. Jumblatt, John G. H. Liu & Ginnie T. North.
`Ocular Effects of Selective Alpha-Adrenergic Agents:
`A New Drug Paradox Tom Mittag, Ph.D.
`Mechanism of Alpha-2-Adrenoceptor Agonist-In
`duced Diuresis Miklos Gellai & Richard M. Edwards.
`Clonidine and Some Bridge Analogues; Cardiovascular
`Effects and Nuclear Magnetic Resonance Data (H/C);
`Pieter B.M.W.M. Timmermans & Pieter A. van Zwi
`
`m
`
`ete.
`
`Alpha-2-Adrenergic Receptors Accelerate Na/H Ex
`change in Neuroblastoma X Glioma Cells' Lori L.
`Isom; E.J. Cragoe, Jr.; and Lee E. Limbird.
`Clonidine: New Research in Psychotropic Drug Phar
`macology; Stuart Fielding, Harbans Lal.
`Clonidine and Related Compounds; Bevyn Jarrott.
`Alpha-2. Adrenergic Agonists: A Newer Class of Anti
`diarrheal Drug Gastroenterology 1986:91:769-75.
`Primary Examiner-Stanley J. Friedman
`Assistant Examiner-Zohreh A. Fay
`Attorney, Agent, or Firm-Gordon L. Peterson; Frank J.
`Uxa, Jr.
`ABSTRACT
`57
`Certain (2-imidazolin-2-ylamino) quinoxalines are dis
`closed. Such quinoxalines reduce or maintain intraocu
`lar pressure when administered directly to the eye of a
`mammal.
`
`28 Claims, No Drawings
`
`

`

`1.
`
`5,021,416
`
`METHOD FOR USING
`(2-MIDAZOLIN-2-YLAMINO) QUINOXALINES
`TO REDUCE OR MANTAIN INTRAOCULAR
`PRESSURE
`
`s
`
`2
`
`X
`
`H
`N
`
`)-N
`N
`
`H
`
`Y
`
`z
`
`N
`rS
`
`12
`N
`
`R
`
`BACKGROUND OF THE INVENTION
`The present invention relates to a method for reduc
`10
`ing or maintaining intraocular pressure. More particu
`larly, it relates to a method for reducing or maintaining
`intraocular pressure involving the administration of an
`effective amount of a (2-imidazolin-2-ylamino) quinoxa
`line and/or a salt thereof, e.g., in an ophthalmically
`acceptable carrier.
`The method of the present invention is particularly
`useful for the management of glaucoma, a disease of the
`eye characterized by increased intraocular pressure. On
`20
`the basis of its etiology, glaucoma has been classified as
`primary or secondary. For example, primary glaucoma
`in adults may be either chronic open-angle or acute or
`chronic angle-closure. Secondary glaucoma results
`from pre-existing ocular diseases such as uveitis, intra
`ocular tumor or an enlarged cataract.
`The underlying causes of primary glaucoma are not
`yet well known. The increased intraocular pressure is
`due to obstruction of aqueous humor outflow. In
`30
`chronic open-angle glaucoma, the anterior chamber and
`its anatomic structures appear normal, but drainage of
`the aqueous humor is impeded. In acute and chronic
`angle-closure glaucoma, the anterior chamber is shal
`35
`low, the filtration angle is narrowed and the iris may
`obstruct the trabecular meshwork at the entrance to the
`canal of Schlemm. Dilation of the pupil may push the
`root of the iris forward against the angle or may pro
`duce pupillary block and thus precipitate an acute at
`tack. Eyes with narrow anterior chamber angles are
`predisposed to acute angle-closure glaucoma attacks of
`varying degrees of severity.
`Secondary glaucoma is caused by any interference
`with the flow of aqueous humor from the posterior
`chambér into the anterior chamber and, subsequently,
`into the canal of Schlemm. Inflammatory disease of the
`anterior segment may prevent aqueous escape by caus
`50
`ing complete posterior synechia in iris bombe, and may
`plug the drainage channel with exudates. Other com
`mon causes are intraocular tumors, enlarged cataracts,
`central retinal vein occlusion, trauma to the eye, opera
`55
`tive procedures and intraocular hemorrhage.
`Considering all types together, glaucoma occurs in
`about 2% of all persons over the age of 40 and may be
`asymptomatic for years before progressing to rapid loss
`of vision. In cases where surgery is not indicated, topi
`cal beta-adrenoceptor antagonists have traditionally
`been the drugs of choice for treating glaucoma.
`Various quinoxaline derivatives have been suggested
`as therapeutic agents. For example, Danielewicz, et al
`U.S. Pat. No. 3,890,319 discloses compounds as regula
`tors of the cardiovascular system which have the fol
`lowing formula:
`
`15
`
`25
`
`where the 2-imidazolin-2-ylamino group may be in any
`of the 5-, 6-, 7- or 8- position of the quinoxaline nucleus;
`X, Y and Z may be in any of the remaining 5-, 6-, 7- or
`8- positions and may be selected from hydrogen, halo
`gen, lower alkyl, lower alkoxy or trifluoromethyl; and
`R is an optional substituent in either tho 2- or 3-position
`of the quinoxaline nucleus and may be hydrogen, lower
`alkyl or lower alkoxy. There is no suggestion in the
`Daniolewicz, et al patent that such compounds are use
`ful in reducing or maintaining intraocular pressure.
`In "Ocular effects of a relatively selective alpha 2
`agonist (UK-14, 304-18) in cats, rabbits and monkeys',
`by J.A. Burke et al, Current Eye Research, Vol. 5, Nov.
`9, 1986, the quinoxaline derivative
`
`/-,
`HN
`NH
`N
`Br
`N
`
`N
`s
`
`N
`
`was shown to be effective to reduce intraocular pres
`sure in rabbits, cats and monkeys. No other quinoxaline
`derivatives were suggested as being useful to reduce
`intraocular pressure.
`SUMMARY OF THE INVENTION
`A new method for reducing or maintaining the intra
`ocular pressure in a mammalian eye has been discov
`ered. This method comprises administering directly to a
`mammalian eye an effective amount of one or more of
`certain (2-imidazoline-2-ylamino) quinoxalines (as de
`fined herein), salts thereof and mixtures thereof. This
`new method is particularly effective in the treatment or
`management of mammalian, e.g., human, eyes affected
`with glaucoma.
`DETAILED DESCRIPTION OF THE
`INVENTION
`The (2-imidazolin-2-ylamino) quinoxalines useful in
`the present invention are those which when adminis
`tered directly into a mammalian eye are effective to
`reduce or maintain, preferably reduce, the intraocular
`pressure in the mammalian eye. Two types of quinoxa
`line derivatives are included within the scope of the
`present invention.
`One type of quinoxaline derivative useful in the pres
`ent invention are those quinoxaline derivatives having
`the formula
`
`45
`
`65
`
`

`

`5,021,416
`4.
`employed. Such a carrier is ophthalmically acceptable if
`it has substantially no long term or permanent detrimen
`tal effect on the eye to which it is administered. Exam
`ples of ophthalmically acceptable carriers include wa
`ter, in particular distilled water, saline and the like aque
`ous media. The presently useful compounds are prefera
`bly administered to the eye as a liquid mixture with the
`carrier. The compounds are more 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 em
`ployed, it is preferred that the mixture contain one or
`more of the presently useful compounds in an amount in
`the range of about 0.0001% to about 1%, more prefera
`bly about 0.05% to about 0.5%, W/V.
`Any method of administering drugs directly to a
`mammalian eye may be employed to provide the pres
`ently useful compound or compounds to the eye to be
`treated. By the term "administering directly' is meant
`to exclude those general systemic drug administration
`modes, e.g., injection directly into the patients blood
`vessels, oral administration and the like, which result in
`the compound or compounds being systemically avail
`able. The primary effect on the mammal resulting from
`the direct administering of the presently useful com
`pound or compounds to the mammal's eye is preferably
`a reduction in intraocular pressure. More preferably,
`the presently useful compound or compounds are ap
`plied 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 ocular
`drops, gels or creams, are preferred because of ease of
`application, ease of dose delivery, and fewer systemic
`side effects, such as cardiovascular hypotension. An
`exemplary topical ophthalmic formulation is shown
`below in Table I. The abbreviation q.S. means a quantity
`sufficient to effect the result or to make volume.
`TABLE I
`Amount(% W/V)
`about 0.0001 to about 1.0
`
`3
`
`R3
`
`NH
`
`HN
`N
`N
`
`R4
`
`Rs
`
`N
`
`s
`
`R2
`
`a
`N
`
`R
`
`5
`
`O
`
`, pharmaceutically acceptable acid addition salts thereof
`and mixtures thereof. R is H, and R2 is selected from
`the group consisting of alkyl radicals containing 1 to 4
`carbon atoms and alkoxy radicals containing 1 to 4
`carbon atoms. R2 is preferably a methyl radical. The
`15
`2-imidazolin-2-ylamino group may be in any of the 5-,
`6-, 7- or 8- positions, preferably in the 6-position, of the
`quinoxaline nucleus. R3, R4 and R5 each is located in
`one of the remaining 5-, 6-, 7- or 8-positions of the qui
`noxaline nucleus and is independently selected from the 20
`group consisting of Cl, Br, Hand alkyl radicals contain
`ing 1 to 3 carbon atoms. R3 is preferably in the 5-posi
`tion of the quinoxaline nucleus, and R4 and R5 are pref
`erably both H. In a particularly useful embodiment R3 is
`Br.
`25
`Another type of quinoxaline derivative useful in the
`present invention are those quinoxaline derivatives hav
`ing the formula
`
`R3
`
`NH
`
`HN
`N
`N
`
`N
`s
`
`R2
`
`e
`N
`
`R
`
`30
`
`35
`
`R4
`Rs
`, pharmaceutically acceptable acid addition salts thereof
`and mixtures thereof. In this formula, R1 and R2 are
`40
`independently selected from the group consisting of H,
`alkyl radicals containing 1 to 4 carbon atoms and alkoxy
`radicals containing 1 to 4 carbon atoms Preferably, both
`R1 and R2 are H. The 2-imidazolin-2-ylamino group
`may be in any of the 6-, 7- or 8- positions, preferably in
`the 6- position, of the quinoxazoline nucleus. R3 is se
`45
`lected from the group consisting of H and alkyl radicals
`containing 1 to 3 carbon atoms. Preferably, R3 is se
`lected from H and methyl. R4 and R5 each is located in
`one of the remaining 6-, 7-, or 8-positions of the quinox
`aline nucleus and is selected from Cl, Br, H and alkyl 50
`radicals containing 1 to 3 carbon atoms. Preferably both
`R4 and R5 are H.
`All stereoisomers, tautomers and mixtures thereof
`which comply with the constraints of one or more of
`the presently useful compounds are included within the 55
`scope of the present invention.
`The present method is particularly effective in a strat
`egy for the treatment or management of glaucoma,
`whether primary or secondary glaucoma. In this em
`bodiment, one or more of the presently useful com
`pounds are preferably administered directly to a mam
`malian eye affected with glaucoma to effectively reduce
`or maintain, preferably control, the intraocular pressure
`in the glaucoma-affected eye.
`The presently useful compounds are often adminis
`65
`tered to the eye in the form of a mixture with an oph
`thalmically acceptable carrier. Any suitable, e.g., con
`ventional, ophthalmically acceptable carrier may be
`
`Ingredient
`(2-imidazolin-2-ylamino)
`quinoxaline
`Preservative
`Vehicle
`Tonicity Adjustor
`Buffer
`pH Adjustor
`antioxidant
`Purified Water
`
`0-0.0
`0-40
`-10
`0.0-0
`q.s. pH 4.5-7.5
`as needed
`as needed to make 100%
`
`Various preservatives may be used in the ophthalmic
`preparation described in Table I above. Preferred pre
`servatives include, but are not limited to, benzalkonium
`chloride, chlorobutanol, thimerosal, phenylmercuric
`acetate, and phenylmercuric nitrate. Likewise, various
`preferred vehicles may be used in such ophthalmic
`preparation. These vehicles include, but are not limited
`to, polyvinyl alcohol, povidone, hydroxypropyl methyl
`cellulose, poloxamers, carboxymethyl cellulose, hy
`droxyethyl cellulose, and purified water.
`. .
`Tonicity adjustors may be added as needed or conve
`nient. They include, but are not limited to, salts, particu
`larly sodium chloride, potassium chloride, mannitol,
`and glycerin, or any other suitable ophthalmically ac
`ceptable tonicity adjustor.
`
`.
`
`

`

`5,021,416
`5
`6
`Warious buffers and means for adjusting pH may be
`catalyst. The container including the suspension was
`used so long as the resulting preparation is ophthalmi
`evacuated and filled with hydrogen three times and the
`cally acceptable. Accordingly, buffers include but are
`suspension was hydrogenated at 18 psi until hydrogen
`not limited to, acetate buffers, citrate buffers, phosphate
`uptake ceased. The reaction was slightly exothermic
`buffers, and borate buffers. Acids or bases may be used
`and one refill of hydrogen was required. The resulting
`to adjust the pH of these formulations as needed.
`light yellow solution, which darkens rapidly on contact
`In a similar vein, ophthalmically acceptable antioxi
`with air, was filtered and concentrated to about 150 ml.
`dants include, but are not limited to, sodium metabisul
`Concentrated hydrochloric acid (12 ml) was added and
`fite, sodium thiosulfate, acetylcysteine, butylated hy
`the solid formed was filtered off. After drying in vacuo
`droxyanisole, and butylated hydroxytoluene.
`overnight, 12 g (a yield of 93%) of purple solid was
`10
`Other excipient components which may be included
`obtained, m.p. 224-5 C. Using various analytical proce
`in the exemplary ophthalmic preparation described in
`dures, this solid was determined to be 1,2,4-triamino
`Table I are chelating agents which may be added as
`benzene dihydrochloride.
`needed. The preferred chelating agent is edetate diso
`6-Aminoquinoxaline
`dium, although other chelating agents may also be used
`Glyoxal sodium bisulfite adduct (Aldrich, 14.3g, 50
`in place of or in conjunction with it.
`minol) was added in small portions to a solution of
`Pharmaceutically acceptable acid addition salts of the
`1,2,4-triaminobenzene dihydrochloride (9.8g, 50 mmol)
`presently useful compounds are those formed from
`in 200 ml of 10% by weight sodium carbonate in water.
`acids which form non-toxic addition salts containing
`The reaction mixture was heated to 100 C. for two
`pharmaceutically acceptable anions, such as the hydro
`20
`hours and then cooled to 0 C. The crystals formed
`chloride, hydrobromide, hydroiodide, sulphate or bisul
`were filtered off and dried in vacuo to give a crude
`fate, phosphate or acid phosphate, acetate, maleate,
`yield of 7.06 g (a yield of 97%) of brown crystals. Re
`fumarate, oxalate, lactate, tartrate, citrate, gluconate,
`crystallization from benzene gave 6.32 g (a yield of
`saccharate and p-toluene sulphonate salts.
`87%) yellow crystals, m.p. 157'-8" C. Using various
`The presently useful compounds may be prepared in
`25
`analytical procedures, these yellow crystals were deter
`accordance with the procedures described in Danielew
`mined to be 6-aminoquinoxaline.
`icz, et al U.S. Pat. No. 3,890,319 for the production of
`6-(2-imidazolin-2-ylamino) quinoxaline
`the quinoxaline derivatives therein. This patent is
`6-Aminoquinoxaline (1.00 g, 7.5 mmol) was sus
`hereby incorporated in its entirety by reference herein.
`Briefly, the presently useful 2-imidazolin-2-ylamino
`pended in 15 ml of water and thiophosgene (0.64 ml, 8.4
`mmol) was added in small portions with vigorous stir
`quinoxaline derivatives may be prepared by (1) reaction
`of the appropriate amino-quinoxaline with thiophos
`ring. The starting material dissolved and after 2 hours
`gene to form the corresponding isothiocyanate; and (2)
`the red color of the solution was discharged. The solid
`reacting this isothiocyanate with excess ethylene di
`formed was removed by vacuum filtration and washed
`amine to form the corresponding beta-aminoethyl-thi
`with water. The crude isothiocyanate thus obtained was
`35
`oureidoquinoxaline, which is then cyclized to the corre
`used without further purification. A solution of the
`sponding derivative. Alternately, such derivatives can
`isothiocyanate in benzene (70 ml) was contacted with
`be prepared by (1) reacting the corresponding
`ethylenediamine (Aldrich, 2.71 g, 45 mmol) in 10 ml of
`aminoquinoxaline with benzoyl isothiocyanate to form
`benzene at 25 C. for 30 minutes. After stirring for an
`the corresponding N-benzoyl thioureido compound,
`additional 30 minutes, the supernatant was poured off.
`followed by hydrolysis to the thioureido compound, or
`The crude thiourea thus obtained was washed three (3)
`reaction of the aminoquinoxaline with ammonium thio
`times with 10 ml dry ether and used directly for the next
`cyanate to form the thioureido compound directly; (2)
`step. The crude product was dissolved in 30 ml of dry
`methylation to form the S-methyl derivative of the
`methanol and the dark green solution was heated at
`thioureido compound; and (3) reaction with ethylene
`reflux for 15 hours until hydrogen sulfide gas was no
`diamine to form the derivative.
`longer evolved. The mixture was cooled to room tem
`For derivatives in which the R3 group is to be alkyl,
`perature and concentrated in vacuo. The resulting dark
`the corresponding bromo derivative can be produced
`green solid was chromatographed (SiO2, 90/10
`and then subjected to an alkylation reaction in which
`CHCl3/CH3OH saturated with NH3 (g)) to yield a dark
`the bromo group is replaced by the desired alkyl group.
`green solid which was recrystallized from CH3OH to
`This alkylation reaction is conveniently conducted
`yield 1.11 g of the title compound as a light green crys
`using an alkylation agent, such as an alkyl metallic com
`talline solid, mp 232"-234 C. The yield was 70%. The
`ponent, e.g., alkyl stannane, in the presence of a plati
`compound was characterized by H. and 13CNMR, IR
`num group metal-containing catalyst. For example, if it
`and mass spectral analysis.
`is desired to substitute a methyl group for the bromo
`55
`EXAMPLE 2
`group, the bromo derivative is contacted with tetra
`methyl tin in the presence of a palladium-containing
`Preparation of 5-methyl-6-(2-imidazolin-2-ylamino)
`catalyst, e.g. (Ph3P)2PdCl2, at conditions to effect the
`quinoxaline
`desired alkylation or substitution.
`6-Amino-5-bromoquinoxaline hydrobromide
`The following non-limiting examples illustrate cer
`6-Aminoquinoxaline (2.08 g, 14.4 mmol) was dis
`tain aspects of the present invention.
`solved in 11.5 ml glacial acetic acid. The solution was
`cooled in water while a solution of bromine (0.74 ml, 2.3
`EXAMPLE 1.
`g, 14.4 mmol) in 1.5 ml glacial acetic acid was added
`Preparation of 6-(2-imidazolin-2-ylamino) quinoxaline
`slowly over 15 min. After stirring for an additional 30.
`1,2,4-Triaminobenzene dihydrochloride
`min, the orange red solid formed was filtered off and
`65
`To a suspension of 4-nitrophenylenediamine (Ald
`washed thoroughly with dry ether. The solid was dried
`in vacuo overnight to yield 4.44 g crude product (a
`rich, 10 g, 65.3 mmol) in absolute ethanol (240 ml) was
`added 600 mg of 10% by weight palladium on charcoal
`yield of 100%). The compound, 6-amino-5-
`
`30
`
`15
`
`45
`
`

`

`5,021,416
`8
`7
`bromoquinoxaline hydrobromide, had no definite melt
`Further purification was achieved by recrystalliza
`ing point. A phase change (from fine powder to red
`tion as described below. The partially purified product
`crystals) was noticed at about 220 C. Decomposition
`from above was dissolved in N,N-dimethylformamide
`was observed at about 245' C. It was used directly for
`(about 17 ml/g) at 100° C. with vigorous stirring. The
`the next step.
`solution was filtered hot and set aside to cool overnight.
`6-Amino-5-Bromoquinoxaline
`The bright yellow crystals were collected by filtration,
`The crude 6-amino-5-bromoquinoxaline from above
`m.p. 252-3 C. Recovery was from 65-77%. Using
`was dissolved in water and saturated sodium bisulfite
`various analytical procedures, the bright yellow solid
`solution was added until the resulting solution tested
`was determined to be 5-brono-6-(2-imidazolin-2-
`negative with starch-iodide paper. The solution was
`ylamino) quinoxaline.
`then basified with 2N sodium hydroxide and extracted
`05-Methyl-6-(2-imidazolin-2-ylamino)quinoxaline
`thoroughly with ethyl acetate. The organic extract was
`A sealable reaction tube was charged with 5-bromo
`dried over magnesium sulfate and concentrated under
`6-(2-imidazolin-2-ylamino) quinoxaline (104 mg., 0.36
`reduced pressure to give the free base. The crude prod
`mmol), tetramethyl tin (214 ng, 1.2 mmol) and
`uct was recrystallized from boiling benzene to give
`15
`(Ph3P)2PdCl2 (10 mg) and dry dimethylformamide (2
`yellow crystals, m.p. 155'-6" C. Using various analyti
`- ml) in a reaction tube. The reaction mixture was purged
`cal procedures, the yellow crystals were determined to
`with dry nitrogen gas. The tube was sealed and heated
`be 6-amino-5-bromoquinoxaline. The yield was 82%.
`5-Bromo-6-isothiocyanatoquinoxaline
`to 145 C. for 6 hours. The reaction mixture was cooled
`The crude hydrobromide product previously noted
`to room temperature and the solvent removed in vacuo.
`20
`The dark brown residue was chromatographed (SiO2;
`(4.27g, 14.0 mmol)Was dissolved in 60 ml of water and
`thiophosgene (Aldrich, 1.28 ml, 16.8 mmol) was added
`5/1 CHCl3/CH3OH saturated with NH3 (g)) to yield
`in small portions with vigorous stirring. After 2 hours,
`46.5 mg (53%) of the title compound as a light yellow
`the red color of the solution was discharged. The solid
`solid. An analytical sample was prepared by recrystalli
`formed was filtered off and washed thoroughly with
`25
`zation from CHCl3/CH3OH and had a melting point of
`water. After drying in vacuo at 25 C., 3.38 g (a yield of
`183-186° C. The compound was characterized by 1H
`90%) of brick red crystals was obtained, m.p. 157-8 C.
`and 13CNMR, IR and mass spectral analysis.
`A portion of this material was further purified by col
`umn chromatography to give white crystals, m.p.
`EXAMPLE 3
`157'-8" C. Using various analytical procedures, these
`Preparation of 2-Methyl-5-bromo-6-(2-imidazolin-2-
`crystals were determined to be 5-bromo-6-isothi
`ylamino)-quinoxaline
`ocyanatoquinoxaline.
`2-Methyl-6-nitroquinoxaline
`5-Bromo-6(-N-(2-aminoethyl)thioureido)quinoxaline
`A solution of pyruvic aldehyde (Aldrich, 40% solu
`A solution of the isothiocyanate (3.25 g, 12.2 mmol)
`tion in H2O, 11.8g, 65.3 mmol) was added dropwise to
`in 145 ml benzene was added to a solution of ethylenedi
`35
`a solution of 4-nitro-1,2-phenylenediamine (Aldrich, 10
`amine (Aldrich, 5.43 g, 90.0 mmol) in 18 ml benzene at
`g, 65.3 mmol) in 150 ml of H2O. The reaction mixture
`25 C, over 2 hours. After stirring for a further 30 min,
`was heated to 80 C. for four hours. The reaction was
`the supernatant was poured off. The oil which remained
`cooled to room temperature, diluted with water and
`was washed by swirling with dry ether three times and
`extracted with CHCl3. The organic extracts were dried
`used directly for the next step.
`over MgSO4 and evaporated to yield 10.7 g (a yield of
`A portion of this product was further purified by
`87%) of as a brick red solid. Using various analytical
`column chromatography (SiO2, CHCl3) for character.
`procedures, this solid was determined to be 2-methyl-6
`ization. A white solid was recovered which decom
`nitroquinoxaline,
`posed at 175 C. with gas evolution (puffing). This
`b 2-Methyl-6-Aminoquinoxaline
`white solid was determined to be 5-bromo-6(-N-2-
`45
`(aminoethyl)thioureido) quinoxaline.
`A thick-walled Parr hydrogenation flask was charged
`5-Bromo-6-(2-imidazolin-2-ylamino)quinoxaline
`with 2-methyl-6-nitroquinoxaline (10.0 g, 52.9 mmol)
`The crude product from above was dissolved in 100
`and CH3OH (200 ml). The flask was flushed with a
`ml dry methanol and the brown solution was refluxed
`stream of nitrogen and 10% by weight palladium on
`for 19 hours until hydrogen sulfide gas was no longer
`charcoal (500mg) was added. The flask was pressurized
`evolved. The mixture was cooled to room temperature
`with hydrogen to 50 psi and maintained at this pressure
`and concentrated to about 50 ml. The yellow solid was
`for three (3) hours. The reaction mixture was filtered
`filtered off and dried in vacuo; weight 2.52 g (a yield of
`and washed through silicon dioxide and concentrated in
`70%), mp 242'-4" C.
`vacuo to yield a tan solid. The crude material was chro
`As the crude product was insoluble in most common
`55
`matographed (SiO2;95/5 CHCl3/CH3OH saturated
`organic solvents, initial purification was achieved by an
`with NH3(g)) and recrystallized from benzene to yield
`acid-base extraction procedure. 23 g of the crude prod
`7.4 g (a yield of 88%) of a tan solid. Using various ana
`uct was dissolved in 100 ml 0.5N hydrochloric acid.
`lytical procedures, this tan solid was determined to be
`The turbid yellow solution was filtered to give a clear
`2-methyl-6-aminoquinoxaline.
`orange yellow solution which was extracted twice with
`60
`2-Methyl-5-bromo-6-(2-imidazolin-2-ylamino) quinoxa
`ethyl acetate (2x 10 ml). The aqueous phase was cooled
`line
`to 0 C. and basified with 6N sodium hydroxide, keep
`By a series of reaction steps analogous to the reaction
`ing the temperature of the solution below 15 C. at all
`steps described above in Example 2 to produce 5
`times. The yellow solid which precipitated was filtered
`brono-6-(2-imidazolin-2-ylamino) quinoxaline, the title
`off and washed thoroughly with water until the wash
`65
`compound (mp. 260 C.) was prepared starting with
`ings were neutral to pH paper. The solid was dried
`2-methyl-6-aminoquinoxaline
`in
`place
`of 6
`overnight in vacuo to give 1.97 g yellow solid, m.p.
`aminoquinoxaline.
`249-50 C. The recovery was about 88%.
`
`30
`
`10
`
`50
`
`

`

`5
`
`9
`EXAMPLE 4
`Preparation of 3-Methyl-5-bromo-6-(2-imidazolin-2
`ylamino)-quinoxaline
`3-Methyl-6-aminoquinoxaline
`Pyruvic aldehyde (Aldrich, 892 mg, 4.95 mmol, 40%
`solution H2O) was added dropwise to a stirred solution
`of 1, 2, 4-triaminobenzene hydrochloride (1.0 g, 4.95
`mmol) dissolved in 10% aqueous Na2CO3 (15 ml). The
`mixture was heated at 100 C. for two hours before
`cooling to room temperature. The mixture was ex
`tracted with CHCl3. The combined organic extracts
`were dried over MgSO4 and concentrated in vacuo to
`yield a brown solid. The crude product was chromato
`graphed (SiO2, 95/5 CHCl3/CH3OH saturated with
`NH3 (g)) to yield 616 mg (a yield of 75%) 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.
`20
`3-Methyl-5-bromo-6-(2-imidazolin-2-ylamino)-quinoxa
`line
`By a series of reaction steps analogous to the reaction
`steps described above in Example 2 to produce 5
`bromo-6-(2 imidazolin-2-ylamino) quinoxaline, the title
`25
`compound (mp>260 C.) was prepared starting with
`3-methyl-6-aminoquinoxaline
`in
`place
`of 6
`aminoquinoxaline.
`
`15
`
`5,021,416
`10
`The solid was washed with water, dried in vacuo and
`chromatographed (SiO2, ethylacetate) to yield 11.7 g
`(86%) of a tan solid, mp 185-186' C. Using various
`analytical procedures, this solid was determined to be
`2,3-dimethyl-6-aminoquinoxaline.
`2,3-dimethyl-5-bromo-6-(2-imidazolin-2-ylamino)-
`quinoxaline
`By a series of reaction steps analogous to the reaction
`steps described above in Example 2 to produce 5
`bromo-6-(2-imidazolin-2-ylamino) quinoxaline, the title
`O
`compound (mp 252-254 C.) was prepared starting
`with 2,3-dimethyl-6-aminoquinoxaline in place of 6
`aminoquinoxaline.
`EXAMPLE 6 to 10
`The five (5) quinoxaline derivatives produced in ac
`cordance with Examples 1 to 5 were tested to determine
`what effect, if any, these materials have 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
`one eye of a drug-naive, unanesthetized New Zealand
`white rabbit in a single 50 micro liter drop. The contra
`lateral eye received an equal volume of saline prior to
`determining the intraocular pressure after the mixture
`was administered. Also, approximately 10 micro liters
`of 0.5% (W/V) proparacaine (topical anesthetic) was
`applied to the corneas of each of the rabbits before
`determining intraocular pressure. As a control test, six
`(6) other drug-naive, unanesthetized New Zealand
`white rabbits were treated and tested as described above
`except that no quinoxaline derivative was included in
`the solutions administered to the eyes.
`The intraocular pressure was determined in both eyes
`of each rabbit before and after the solutions were ad
`ministered. Such intraocular pressure determinations
`were made in the conventional manner using conven
`tional equipment.
`Results of these IOP determinations were as follows:
`
`30
`
`EXAMPLE 5
`Preparation of
`2,3-dimethyl-5-brono-6-(2-imidazoline-2-ylanino,
`quinoxaline.
`2,3-Dimethyl-6-aminoquinoxaline
`35
`2,3-butanedione (7.03 g, 81.7 mmol) was added to a
`solution of 1,2,4-triaminobenzene hydrochloride (16.5
`g, 81.7 mmol) in aqueous 10% Na2CO3(200 ml). The
`reaction mixture was stirred at room temperature for 15
`minutes during which time a yellow precipitate formed.
`The reaction mixture was stirred for an additional 30
`minutes before collecting the solid by vacuum filtration.
`
`Active
`Material
`
`Example
`6.
`
`/-,
`
`Difference In Intraocular Pressure, percent
`Initial Effect
`Maximun Effect
`Maximum Effect
`On Treated Eye On Treated Eye
`On Untreated Eye
`
`18 -
`
`8
`
`- 18.6
`
`3.2
`
`--9.6
`
`4
`
`HN
`
`NH
`
`Y N
`
`N
`
`s
`
`N
`
`7.
`
`N.S.
`
`-21.9 - 3.6
`
`-5.4
`
`2.0
`
`HN
`N
`N
`
`NH
`CH3
`
`N
`
`

`

`Active
`Material
`
`8.
`
`/-,
`
`HN
`N
`N
`
`NH
`Br
`
`11
`
`5,021,416
`
`12
`
`-continued
`Difference. In Intraocular Pressure, percent
`Initial Effect
`Maximum Effect
`Maximum Effect
`On Treated Eye On Treated Eye
`On Untreated Eye
`
`N.S.
`
`N.S.
`
`N.S.
`
`N
`
`s l N
`
`CH3
`
`9
`
`/-
`
`N.S.
`
`--22.5 h 1.8
`
`N.S.
`
`HN
`
`NH
`n1 Br
`I
`N
`
`N
`NS
`
`CH3
`
`N
`
`O.
`
`/-
`
`N.S.
`
`N.S.
`
`N.S.
`
`HN
`
`N
`N
`
`NH
`Br
`
`CH3
`
`CH3
`
`Control
`
`N.S.
`
`N.S.
`
`N.S.
`
`N.S. means that the effect was not statistically signifi
`Cant.
`35
`These results indicated that the quinoxaline deriva
`tives used in Examples 6, 7 and 9 are effective to reduce
`intraocular pressure in the treated rabbit eye, i.e., the
`eye to which the active material was directly adminis
`tered. The quinoxaline derivative used in Example 6
`had an initial effect in the treated eye of raising the
`intraocular pressure. These results are particularly sur
`prising in view of the insignificant effect on intraocular
`pressure of the materials used in Examples 8 and 10,
`which materials are structurally closely related to the
`other materials tested.
`While this invention has been described with respect
`to various specific examples and embodiments, it is to be
`understood that the invention is not limited thereto and
`that it can be variously practiced within the scope of the
`following claims.
`What is claimed is:
`1. A method for reducing or maintaining the intraoc
`ular pressure in a mammalian eye comprising adminis
`tering directly to a mammalian eye an amount effective
`to reduce or maintain the intraocular pressure in the
`mammalian eye of a compound selected from the group
`consisting of those having the formula
`
`45
`
`50
`
`55
`
`R3
`
`NH
`
`HN
`N
`N
`
`R4
`
`R5
`
`N
`was
`
`R2
`
`e
`N
`
`R
`
`65
`
`, and p