Abstract:
3-chloro-4-(4,5-dihydro-1H-imidazao-2-yl)-amino-5-alkylbenzoic acid, its pharmaceutically acceptable metal salts and esters are useful in treating glaucoma by virtue of the effect in lowering intraocular pressure when administered systemically or topically to the eye. Also disclosed are processes for preparing the compounds, pharmaceutical compositions comprising the disclosed compounds; and methods of treatment comprising administering said compositions when a lowering of intraocular pressure is indicated.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of Ser. No. 590,464, filed Mar. 16, 1984, now abandoned, which is a continuation-in-part of both Ser. No. 519,791, filed Aug. 3, 1983, now U.S. Pat. No. 4,517,199, and Ser. No. 520,071, filed Aug. 3, 1983, now U.S. Pat. No. 4,515,800, which are continuation-in-parts of Ser. No. 323,369, filed Nov. 20, 1981, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to certain substituted dihydro-1H-imidazoyl benzoic acids and esters which are useful in lowering intraocular pressure, and thus are useful in treating glaucoma. 
     BACKGROUND 
     Some medicaments presently available for treating glaucoma by lowering the intraocular pressure are not completely satisfactory because they are ineffective, and/or demonstrate unwanted cardio-vascular-pulmonary and CNS activities. Additionally, prior art compounds for this use plague the user with any one or more of the following side effects: obvious vasoconstricton or vasodilation of the vessels of the sclera; obvious pupil contraction or dilation; and painful stinging. Accordingly, there is a need in the art for compositions which are effective in lowering intraocular pressure and are devoid of unwanted side effects. Such freedom of side effects is particularly desired on topical administration to the eye. 
     SUMMARY OF THE INVENTION 
     It is accordingly one object of the invention to provide novel 3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-alkyl benzoic acids and esters, salts and methods of preparation. 
     A further object of the invention is to provide novel pharmaceutical compositions of matter containing these benzoic acids and esters as the effective ingredient, and methods for treating glaucoma by administration of these novel compositions. 
     Other objects and advantages of the present invention will become apparent as the description thereof proceeds. 
     In satisfaction of the foregoing objects and advantages, the present invention provides 3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)amino-5-alkylbenzoic acids, salts and the esters, which are useful in lowering intraocular pressure when administered topically or systemically to the eye and, thus, are useful in treating glaucoma; the novel compounds being of the following general formula: ##STR1## wherein R is methyl or ethyl and the pharmaceutically acceptable salts and esters thereof. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     As indicated above, the present invention relates to novel substituted 4,5-dihydro-1H-imidazo-2-yl benzoic acids and derivatives. These compounds may be characterized by the following general formula: ##STR2## wherein R is methyl or ethyl and the pharmaceutically acceptable esters and salts thereof. The pharmaceutically acceptable acid addition salts from mineral acids or organic acids are also included with the scope of the invention. 
     The esters contemplated for the compounds of the invention include any ester moiety which permits the compound to retain its pharmaceutical use in lowering intraocular pressure, and provides a compound which is safe and effective. Thus the compounds covered by the above general formula include the free acid (--COOH), alkali and alkaline earth metal salts (e.g., Na, K, C 2 , and Mg), and esters which may be illustrated by the functional group --COOR&#39;. The invention is inclusive of all ester radicals, R&#39;, known to be effective as pharmaceutically acceptable esters. Lower alkyl esters are especially preferred. The pharmaceutically acceptable salts of the compounds of the present invention also include N-acid addition salts, such as the hydrochloride, hydrobromide, maleate, hydrogen sulfate, and the like. 
     As pointed out, the ester moiety may be any compatible group. More generally stated, pharmaceutically acceptable carboxyl derivatives of the present invention are those derived by reacting the free acid or salt derivative with alcohols, phenols, alkylating reagents and the like. For example, esters of interest from the above-listed starting materials are final products having the --COOR&#39; group at the ester position, wherein R&#39; is alkyl having 1-10 carbon atoms, straight or branched, such as methyl, ethyl, t-butyl, pentyl, decyl and the like; aminoalkyl including 2-methylaminoethyl, 2-diethylaminoethyl, 2-acetamidoethyl, phthalimidomethyl, succinimidomethyl; alkoxyalkyl wherein the alkoxy portion as 1-10 and preferably 1-6 carbon atoms; but can be branched, straight or cyclic, and the alkyl portion has 1-6 carbon atoms, such as methoxymethyl, ethoxymethyl, isopropoxymethyl, decyloxymethyl, ethoxymethyl, isopropoxymethyl, decyloxymethyl, ethoxypropyl, decyloxypentyl, cyclohexyloxymethyl and the like; alkanoloxyalkyl wherein the alkanoyloxy portion is straight or branched and has 1-6 carbon atoms and the alkyl portion has up to 16 carbon atoms, such as acetoxymethyl, pivaloyloxymethyl, acetoxyethyl, propionyloxyethyl, acetoxypropyl, and the like; haloalkyl wherein halo is chloro, bromo, fluoro, or iodo, and the alkyl portion is straight or branched having 1-6 carbon atoms, e.e., 2,2,2-trichloroethyl, trifluoroethyl, 2-bromopropyl, diiodomethyl, 2-chloroethyl, 2-bromoethyl, and the like; alkenyl having 1-10 carbon atoms, either straight or branched, e.g., allyl, 2-propenyl, 3-butenyl, 4-butenyl, 4-pentenyl, 2-butenyl, 3-pentenyl, 3-methyl-3-butenyl, methallyl, 1,4-cyclohexadien-1-yl-methyl, and the like; alkynyl having 1-10 carbon atoms, either straight of branched, e.g., 3-pentynyl, propargyl, ethynyl, 3-butyn-1-yl, and the like; alkanoyl, either straight or branched, having 1-10 carbon atoms, such as pivaloyl, acetyl, propionyl, and the like, aralkyl or heteroaralkyl wherein alkyl has 1-3 carbon atoms, and hetero means 1-4 hetero-O-atoms, including benzyl, benzhydryl, and substituted benzyl and benzyhdryl, for e.g., benzyl or benzhydryl substituted with 1-3 substituents such as benzyl, phenoxy, halo, loweralkyl, loweralkanoyloxy of 1-5 carbon atoms, lower alkoxy, hydroxy, nitro, blocked carboxy, or combinations thereof, e.g., p-chlorobenzyl, o-nitrobenzyl, 3,5-dinitrobenzyl, p-methoxybenzyl, m-benzoylbenzyl, p-t-butylbenzyl, m-phenoxybenzyl, p-benzoylbenzyl, p-nitrobenzyl, 3,5-dichloro-4-hydroxybenzyl, p-methoxycarbonylbenzyl, p-methoxybenzhydryl, p-carboxybenzyl, the latter being either the free acid, ester or the sodium salt, 2,4,6-trimethylbenzyl, p-pivaloyloxybenzyl, p-t-butoxycarbonyl benzyl, p-methylbenzyl, p-benzoyloxybenzyl, p-acetoxybenzyl, p-2-ethylhexanoylbenzyl, p-ethoxycarbonylbenzyl, p-benzoylthiobenzyl, p-benzamidobenzyl, o-pivaloyloxybenzyl, m-pivaloyloxybenzyl, p-isopropoxybenzyl, p-t-butoxybenzyl, as well as the cyclic analogues thereof, 2,2-dimethyl-5-coumaranmethyl, 5-indanylmethyl, p-trimethylsilybenzyl, 3,5-bis-t-butoxy-4-hydroxybenzyl; 2-thienylmethyl, 2-furylmethyl, 3-t-butyl-5-isothiazolmethyl, 6-pivaloyloxy-3-pyridazinylethyl, 5-phenylthio-1-tetrazolylmethyl, or the like (the use of the terms lower alkyl or lower alkoxy in this context means 1-4 carbon atom chains); or phthalidyl; or phenylethyl, 2-(p-methylphenyl)ethyl, and the arylthioalkyl analogues, aryloxyalkyl wherein aryl is preferably a phenyl ring having 0-3 substituents, preferably 0 or 1 substituents in the ortho or para positions and alkyl is 1-6 carbon atoms, e.g., (4-methoxy)-phenoxymethyl, phenoxymethyl, (4-chloro)phenoxymethyl, (4-nitro)phenoxymethyl, (4-benzyloxy)phenoxymethyl, (4-methyl)phenoxymethyl, (4-benzyloxy)phenylthiomethyl, phenylthioethyl; aryl and alkaryl wherein aryl is phenyl, naphthyl, 5-indanyl, or substituted phenyl having 0-3 substituents, preferably 0 or 1 substituent in the ortho or para position, e.g., (4-methyl)phenyl, (4-hydroxy)phenyl, (4-t-butyl)phenyl, p-nitrophenyl, 3,5-dinitrophenyl, or p-carboxyphenyl, the latter being either the free acid or the sodium salt form; aralkenyl wherein aryl is phenyl and alkenyl has 1-6 carbon atoms, such as 3-phenyl-2-propenyl; aralkoxyalkyl wherein aralkoxy is benzyloxy, and alkyl has 1-3 carbon atoms, such as benzyloxymethyl, (4-nitro)benzyloxymethyl, (4-chloro)benzyloxymethyl; alkylthioalkyl wherein the alkylthio portion has 1-10 and preferably 1-6 carbon atoms, but can be branched, straight or cyclic, and the alkyl portion has 1-6 carbon atoms, such as methylthioethyl, ethylthioethyl, cyclohexylthiomethyl, decylthiobutyl, methylthiopropyl, isopropylthioethyl, methylthiobutyl and the like. 
     In the more preferred embodiment, R&#39; is hydrogen, alkali metal, alkaline earth metal, straight or branch-chain lower alkyl, wherein the alkyl group has 1-6 carbon atoms, lower cycloalkyl, e.g., of 3-7 carbons such as cyclopropyl or cyclohexyl, lower cycloalkylalkyl of 4-8 carbons, e.g., cyclopropylmethyl, alkenyl of 2-7 carbons, e.g., propenyl, aryl of 5-13 carbons, e.g., phenyl, substituted aryl, e.g., anisolyl, such as those of the formula: ##STR3## where X is halogen, methoxy, lower alkyl, e.g., methyl, and n is an integer of 1 to 5; or arylalkyl of 6-14 carbons, e.g., benzyl. The alkali metal may be Na, K or Li, and the alkaline earth metal may be Mg or Ca. 
     Preferred moieties for R&#39; are methyl, ethyl, isopropyl, cyclopropyl, cyclopropylmethyl, cyclobutyl, isobutyl, and t-butyl. 
     It will be noted that the structural formula provided above is tautomeric in the double bond at the amino group attached to the imidazo-2-yl ring. The nomenclature set forth herein however is preferred. 
     The most preferred compounds within the scope of the invention include 3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-methyl benzoic acid and its ethyl ester. 
     The following compounds are also preferred: 
     3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-ethyl benzoic acid ethyl ester 
     3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-methyl benzoic acid isopropyl ester 
     3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-methyl benzoic acid cyclopropyl ester 
     3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-methyl benzoic acid t-butyl ester 
     3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-ethyl benzoic acid isopropyl ester. 
     The compounds of the present invention are useful in lowering intraocular pressure and thus are useful in the treatment of glaucoma. The compounds are essentially devoid of unwanted side effects such as vasoconstriction or vasodilation of the vessels of the sclera, pupil contraction or dilation, and painful stinging. 
     The compounds are preferably administered topically although other conventional methods may be used. In forming compositions for topical administration, the compounds are preferably formulated as 0.1 to 2.0 weight percent solutions in water at a pH of 4.5 to 8.0. While the precise regimen is left to the discretion of the clinician, it is recommended that the resulting solution be topically applied by placing one drop in each eye two times a day. 
     The compounds of the invention may be prepared from 1-acetyl imidazolidin-2-one and 4-amino-3-halo-5-alkylbenzonitrile by reaction in the presence of POCl 3  to produce 4-(1-acetyl-4.5-dihydro-1H-imidazo-2-yl)amino-3-halo-5-alkyl benzonitrile. This intermediate is then reacted with hydrochloric acid to effect deacetylation and remove the 1-acetyl group and also hydrolyze the nitrile group to carboxyl to form the free carboxylic acid. Alkali metal salts and alkaline earth metal salts of the acid may be formed conventionally. The acid or salt may be subsequently esterified with the appropriate alcohol, e.g., a C 1  to C 5  alkyl alcohol to yield the final ester products. 
     In a similar manner other carboxylic acid esterifications may be effected as is known in the art employing other lower alkyl, cycloalkyl, cycloalkylalkyl, aryl, or arylalkyl, alcohols such as isopropanol, cyclopropanol, cyclopropylmethanol, phenyl, or benzyl alcohol, as exampled by the preparation of 3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)amino-5-methylbenzoic acid isopropyl ester prepared by the reaction of isopropanol and 3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)amino-5-methylbenzoic acid with the elimination of water. Since such esterification reactions are well known, they are not further described here. Acid addition salts of the final products may be formed by reaction with the appropriate mineral acid or organic acid by means known in the art. 
     The following examples are presented to illustrate the invention. In these examples and throughout the specification, parts are by weight unless otherwise indicated. Temperatures are in Celcius. 
    
    
     EXAMPLE 1 ##STR4## 
     To a suspension at 1-acetyl imidazolidin-2-one (0.1 mole, 12.8 g) in phosphorous oxychloride (120 ml, 75° C.) was added 4-amino-3-chloro-5-methylbenzonitrile (0.1 mole, 16.6 g) in portions over a 45 minute period while maintaining the temperature at 75° C. The mixture was heated at 75°-80° C. for 18 hours and the phosphorous oxychloride was removed by evaporation in vacuo, the residue was poured onto ice (600 ml), the pH adjusted to 12 and the mixture extracted with chloroform. The combined extracts were dried (magnesium sulfate) and evaporated to a crude solid. An analytical sample was prepared by recrystallization from toluene: mp 184, 5°-186° C.; MS m/e 276 (m+). 
     Analysis. Calculated C 13  H 13  ClN 4  O: C, 56.42; H, 4.73; N, 20.25. Found: C, 56.24; H, 4.76; N, 19.95. 
     EXAMPLE 2 ##STR5## 
     A suspension of 4-(1-acetyl-4,5-dihydro-1H-imidazo-2-yl)amino-3-chloro-5-methylbenzonitrile (28.9 m mole, 8.15 g) in 9N hydrochloric acid was heated at reflux temperature for 8 hours and cooled to room temperature. The solid was collected by filtration, washed with water and air dried. Recrystallization from methanol-ether gave 5.3 g of analytically pure material; mp 320° C. 
     Analysis. Calculated for C 11  H 13  Cl 2  N 3  O 2  : C, 45.53; H, 4.52; N, 14.48. Found: C, 45.67; H, 4.65; N, 14.34. 
     EXAMPLE 3 ##STR6## 
     To a suspension of 3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)amino-5-methylbenzoic acid hydrochloride (8.6 m mole, 2.5 g) in ethanol (37 ml) at room temperature was added borontrifluoride etherate (20.3 m mole, 2.5 ml); this mixture was heated at reflux temperature for 16 hours. The reaction mixture was cooled (10° C.) and poured into a saturated aqueous solution of sodium bicarbonate (65 ml) and the pH of this mixture was adjusted to 9. The opaque solution was extracted with chloroform, the extracts were combined, dried, and evaporated to a solid. Recrystallization from acetonitrile provided 1.7 g of analytically pure material: mp 228°-229.5° C.; MS m/e 281 (m+). 
     Analysis. Calculated for C 13  H 16  ClN 3  O 2  : C, 55.42; H, 5.73; N, 14.91. Found: C, 55.29; H, 5.80; N, 14.78. 
     EXAMPLES 4-8 
     Using the general esterification procedure and starting benzoic acid salt starting material of Example 3, the following esters are prepared using the indicated alcohol 
     EXAMPLE 4 
     Esterification with ethyl alcohol: 3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-ethyl benzoic acid ethyl ester. 
     EXAMPLE 5 
     Esterification with isopropyl alcohol: 3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-methyl benzoic acid isopropyl ester. 
     EXAMPLE 6 
     Esterification with cyclopropanol: 3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-methyl benzoic acid cyclopropyl ester. 
     EXAMPLE 7 
     Esterification with t-butyl alcohol: 3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-methyl benzoic acid t-butyl ester. 
     EXAMPLE 8 
     Esterification with cyclopropyl methanol: 3-chloro-4-(4,5-dihydro-1H-imidazo-2-yl)-amino-5-ethyl benzoic acid cyclopropyl methyl ester. 
     EXAMPLE 9 
     The following are representative pharmaceutical compositions of the preferred compound of Example 3 of the invention for topical use in lowering of intraocular pressure. 
     
         ______________________________________COMPOSITION AIngredient        Percentage by Weight______________________________________1.0% w/v of the compound             1.0of Example 3Benzalkonium chloride             0.01Sodium acetate    0.07Sodium chloride   0.6Hydrochloric acid and/or             to adjust pH to 5.0sodium hydroxide  to 5.5Purified Water    q.s. to 100%______________________________________ 
    
     
         ______________________________________COMPOSITION BIngredient        Percentage by Weight______________________________________1.5% w/v of the compound             1.5of Example 3Benzalkonium chloride             0.01Dried sodium phosphate             0.01Sodium biphosphate             0.07Sodium chloride   0.18Sodium hydroxide and/or             to adjust pHhydrochloric acidPurified Water    q.s. to 100%______________________________________ 
    
     
         ______________________________________COMPOSITION CIngredient         Percentage by Weight______________________________________0.5% w/v of the compound              0.5of Example 3Benzalkonium chloride              0.01Sodium acetate     0.14Disodium edetate   0.01Sodium chloride    0.52Hydrochloric acid and/or              to adjust pHsodium hydroxideHydroxypropylmethylcellulose              0.5Purified Water     q.s to 100%______________________________________ 
    
     The invention has been described herein by reference to certain preferred embodiments. However, as obvious variations thereon will become apparent to those skilled in the art, the invention is not to be considered as limited thereto.