5-[N-methoxyethyl-N-methoxyethoxyethyl)aminomethyl]thieno [2,3-b] thiophene-2-sulfonamide as antiglaucoma agents

Abstract: This invention relates to novel aromatic sulfonamides useful in the treatment of elevated intraocular pressure. More particularly this invention relates to the compounds having the structural formula: as well as the pharmaceutically and ophthalmo­ logically acceptable salts thereof. This invention also relates to pharmaceutical compositions and the use thereof for systemic and ophthalmic use employing the novel compound of this invention as active ingredient for the treatment of elevated intraocular pressure, especially when accompanied by pathological damage such as in the disease known as glaucoma. The invention also relates to processes for preparation of the novel compound.

Description: BACKGROUND OF THE INVENTION Glaucoma is an ocular disorder associated with elevated intraocular pressures which are too high for normal function and may result in irreversible loss of visual function. If untreated, glaucoma may eventually lead to blindness. Ocular hypertension, i.e., the condition of elevated intraocular pressure without optic nerve head damage or characteristic glaucomatous visual field defects, is now believed by many ophthalmologists to represent the earliest phase of glaucoma. Many of the drugs formerly used to treat glaucoma proved not entirely satisfactory. Indeed, few advances were made in the treatment of glaucoma since pilocarpine and physostigmine were introduced. Only recently have clinicians noted that many ß-adrenergic blocking agents are effective in reducing intraocular pressure. While many of these agents are effective in reducing intraocular pressure, they also have other characteristics, e.g. membrane stabilizing activity, that are not acceptable for chronic ocular use. (S)- tert -Butylamino-3-[(4-morpholino-1,2,5-thiadiazol-3-yl)oxy]-2-propanol, a ß-adrenergic blocking agent, was found to reduce intraocular pressure and to be devoid of many unwanted side effects associated with pilocarpine and, in addition, to possess advantages over many other ß-adrenergic blocking agents, e.g. to be devoid of local anesthetic properties, to have a long duration of activity, and to display minimal tolerance. Although pilocarpine, physostigmine and the ß-blocking agents mentioned above reduce intraocular pressure, none of these drugs manifests its action by inhibiting the enzyme carbonic anhydrase and, thereby, impeding the contribution to aqueous humor formation made by the carbonic anhydrase pathway. Agents referred to as carbonic anhydrase inhibitors, block or impede this inflow pathway by inhibiting the enzyme, carbonic anhydrase. While such carbonic anhydrase inhibitors are now used to treat intraocular pressure by oral, intravenous or other systemic routes, they thereby have the distinct disadvantage of inhibiting carbonic anhydrase throughout the entire body. Such a gross disruption of a basic enzyme system is justified only during an acute attack of alarmingly elevated intraocular pressure, or when no other agent is effective. Despite the desirability of directing the carbonic anhydrase inhibitor only to the desired ophthalmic target tissue, no topically effective carbonic anhydrase inhibitors are available for clinical use. However, topically effective carbonic anhydrase inhibitors are reported in U.S. Patents 4,386,098; 4,416,890; and 4,426,388. The compounds reported therein are 5 (and 6)-hydroxy-2-benzothiazolesulfonamides and acyl esters thereof. Closely related compounds are also found in U.S. Patent 4,806,562 and EP publication 0307084. EP-A-0189690 describes a class of compounds in which a six-membered ring is fused to a five-membered heterocyclic ring. US-4751231, meanwhile, describes a class of compounds containing a pyrrole ring fused to a thiophene ring. By definition, therefore, neither of these publications discloses any compounds based on two fused thiophene rings. Moreover, there is no disclosure in either of these documents of a compound possessing an aminomethyl side-chain whose nitrogen atom is substituted by an alkoxyalkoxyalkyl group. DETAILED DESCRIPTION OF THE INVENTION The novel compound of this invention has structural formula: or a pharmaceutically acceptable salt thereof. The novel process for preparing the novel compound of this invention is illustrated as follows: The process comprises treating the aldehyde, 1 , in the presence of an acid such as HCl gas with the amine H₂NR¹ or HNR¹R² at about 15 to 60°C in a C₁₋₃ lower alkanol solvent such as methanol or ethanol for about 0.5 to 72 hours. The crystalline precipitate is treated with a complex metal hydride such as sodium cyanoborohydride at about 0 to 20°C and continuing stirring for about 0.5 to 72 hours. Alternatively, the crystalline precipitate, 2, may be isolated by filtration and resuspended prior to treatment with the hydride. The novel pharmaceutical formulations of this invention are adapted for topical ocular administration in the form of solutions, ointments, solid water soluble polymeric inserts, or solutions which gel at body temperature or in the presence of lachrymal fluids for the treatment of glaucoma and other stages of elevated intraocular pressure and contain about 0.1% to 15% by weight of medicament, the remainder being comprised of carriers and other excipients well known in the art. The medicament in the novel topical ocular formulations comprises the novel compound of this invention either alone or in combination with a β-adrenergic blocking agent such as timolol maleate or a parasympathomimetic agent such as pilocarpine. In such combinatins each of the active agents is present in an amount approximating that found in its single entity formulations. The novel method of treatment of this invention comprises the treatment of elevated intraocular pressure by the administration of an effective amount of the novel compound of this invention or a pharmaceutical formulation thereof. Of primary concern is the treatment by topical ocular administration of about 0.1 to 25 mg and especially 0.2 to 10 mg of such compound per day, either by single dose or on a 2 to 4 dose per day regimen. EXAMPLE 1 5-[(N-Methoxyethyl-N-methoxyethoxyethyl)aminomethyl]-thieno[2,3-b]thiophene-2-sulfonamide Step A : Preparation of Methyl [3-(2-dioxolanyl)-thiophene-2-ylthio]acetate Thiophene-3-carboxaldehyde ethylene acetal (15.62 g, 0.1 mol) was dissolved in dry THF (200 ml) in an inert atmosphere and cooled to -74°C. n-Butyl lithium (44 mL of a 2.3 M solution in hexane; 0.1 mol) was added at a rapid drip rate over 20 minutes (the temperature rose to -68°C). After the addition was complete, the mixture was stirred at -60°C to -74°C for 35 minutes. After about 5 minutes, the lithium derivative began to crystallize. Most crystallized after 35 minutes. Sulfur (as a fine powder; 3.21 g, 0.1 mol) in 1 g and 2.21 g portions was added 5 minutes apart (temperature rose from -74° to -65°C). The reaction was stirred at -74°C for 15 minutes and slowly warmed with stirring to -50°C where it was held for 15 minutes then warmed to -38°C over 15 minutes. Methyl bromoacetate (9.9 mL, 16.1 g, 0. 105 mol) was added at a slow drip rate over a period of 8 minutes (temperature rose from -40°C to -25°C) and the reaction mixture was allowed to stir at ambient temperature until the temperature rose to 0°C). After warming to 24°C the reaction mixture was stirred at room temperature for 2 hours. The reaction was worked up by evaporating the solvent in vacuo and partitioning the residue between ether (250 mL) and water (100 mL). The ether was extracted with water (3 x 25 mL), dried (MgSO₄), filtered, and the solvent evaporated in vacuo to leave 23.36 g of crude methyl [3-(2-dioxolanyl)-thiophene-2ylthio]acetate which was used in the next step without purification. Theoretical Mass, for C₁₀H₁₂O₄S₂:260.0177150; Found: 260.0177150; ¹H NMR(CDCl ) ω, 3.56 (2H, s); 3.71 (3H, s); 4.04 92H, m); 4.15 (2H, m); 6.08 (1H, s); 7.16 (1H, d, J = 6Hz); 7.37 (1H, d, J=6Hz). Step B: Preparation of Methyl (3-Formylthiophene-2-ylthio)acetate To a solution of methyl [3-2-dioxolanyl)thiophene-2-ylthio]acetate (23.36 g) in acetone (100 mL) was added p-toluenesulfonic acid (0.25 g) and the reaction mixture was stirred at room temperature for 1 hour. A saturated aqueous solution of sodium bicarbonate (4 mL) was added with stirring followed by the addition of water (50 mL). After stirring for 10 minutes, the acetone was evaporated in vacuo to leave a gum and water. The gum was dissolved in ether (500 mL) and extracted with water (4 x 50 mL), dried (MgSO ) , filtered and the solvent was evaporated in vacuo to leave 19.77 g of oily methyl (3-formylthiophene-2-ylthio)acetate which was used in the next step without purification. Step C: Preparation of methyl thieno[2,3-b]thiophene-2-carboxylate To a solution of methyl (3-formylthiophene-2-ylthio]acetate (19.31 g, 91 mmol) in methanol (150 mL) was added 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) (1 mL, 1 g, 8.05 mmol) and the stirred reaction flask was immediately immersed in an ice-water bath. Stirring was continued for 30 minutes and the mixture was filtered to give a tacky solid product which was washed with a little cold (-20°C) methanol. The solvent was evaporated in vacuo from the mother liquor and the residue was partitioned between ether and aqueous sodium bicarbonate. The water layer was washed with ether twice, and the combined ether extracts were dried (MgSO₄), filtered, and the solvent evaporated in vacuo to give an oil which solidified when triturated with a little cold (-20°C) methanol. This was combined with the original solid product to give a total of 14.55 g of methyl thieno[2,3-b]thiophene-2-carboxylate, m.p. 101-105°C. Recrystallization from methanol gave product with m.p. 106-107°C. Step D: Preparation of 2-Hydroxymethylthieno[2,3-b]thiophene A solution of methyl thieno[2,3-b]thiophene-2-carboxylate (19.8 g, 0.1 mol) in dry ether (750 mL) was added at a rapid drip rate (1 hour, 45 minutes) to a suspension of lithium aluminum hydride (7.59 g, 0.2 mol) in ether (500 mL) cooled in an ice-water bath. During the addition, precipitated material on the inside of the flask was kept suspended in the reaction medium. After the addition was complete stirring was continued at room temperature for 3 hours. The reaction mixture was cooled in an ice-water bath and there was added in succession, slowly, dropwise with vigorous stirring: water (7.6 ml); 20% aqueous NaOH (22.8 mL); water (7.6 mL); water (4 mL); 20% sodium hydroxide (12 mL); water (4 ml). Vigorous stirring was continued until a granular precipitate was obtained. The ether was decanted and the solids were washed by decantation three times with ether. The combined ether fractions were dried (MgSO₄), filtered, and evaporated in vacuo to leave 16.33 g of white, solid 2-hydroxymethylthieno[2,3-b]thiophene, m.p. 85-87°C. Recrystallization from hexane gave material with m.p. 86-87°C. Step E: Preparation of Thieno[2,3-b]thiophene-2-carboxaldehyde 2-Hydroxymethylthieno[2,3-b]thiophene (16.33 g, 95.9 mmol) dissolved in methylene chloride (165 mL) was added all at once to a stirred suspension of pyridinium chlorochromate (31.0 g, 143.9 mmols) in methylene chloride (172 mL) and stirring was continued at ambient temperature for 2 hours. The mixture was diluted with ether (288 mL) and the supernatant was decanted. The solids were washed three times by trituration with ether. The combined ether extracts were filtered through a 60 x 150 mm silica gel (230-400 mesh) column under pressure and followed with 3 portions of ether. The ether phase of the combined filtrates was evaporated in vacuo to give 13.86 g, of thieno [2,3-b]thiophene-2-carboxaldehyde, m.p. 43-45°C. Sublimation at 108°C bath temperature and 0.5 mm pressure gave 13.10 g, m.p. 47-48°C. Step F: Preparation of 5-[(N-Methoxyethyl-N-methoxyethoxyethyl)aminomethylp)thieno[2,3-b]thiophene-2sulfonamide N-Methoxyethyl-N-methoxyethoxyethylamine (36.0 g., 203 mmoles) was dissolved in methanol (112 ML). To this solution was added methanolic HCl(5.554 M in CH₃OH)(28.2 mL, 157 mmoles) and this was stirred for 10 minutes. 5-Formylthieno[2,3-b]thiophene-2-sulfonamide(8.80 g., 35. 6 mmoles) was added and the mixture was stirred for 14 hours. 4°A sieves (23.7 g.) were added and the mixture under Argon was stirred for an additional 6 days. Sodium cyanoborohydride (4.47 g. 71.2 mmoles) was added and this was stirred under Argon for 48 hours. Methanol (250mL) and TEF(250 mL.) were added to dissolve all the product. The solution was then filtered through a pad of celite and all solvent was evaporated in vacuo . H₂O (100 mL) was added followed by the slow addition of conc. HCl (100 mL). The liquid was decanted and filtered from solid. The acid solution of product was saved. More product was recovered from insoluble material by dissolving the insoluble material in THF (100 mL). Conc. HCl (25 mL) was added and the solution heated to reflux three times in a 15 minute interval. 100 ml of water was added and the THF evaporated off. A clear solution was decanted from the insoluble material. To the combined acidic water solution of product was added conc. NH₄OH until pH was 8.5 (125 mL), and this was then extracted five times with ether (150 ml ea). The combined extracts were dried over MgSO₄. The solvent was filtered and evaporated in vacuo to leave 10.16 g of crude product, which was chromatographed on 2.4 kg. of silica gel, eluting with 3% methanol in chloroform to give 7.7 g of highly pure 5-[(N-methoxyethyl-N-methoxy yethoxyethyl)aminomethyl]thieno[2,3-b]thiophene-2-sulfonamide. Step G: Preparation of 5-[(N-Methoxyethyl-N-methoxyethoxyethyl)aminomethyl]thieno[2,3-b]thiophene-2-sulfonamide hydrochloride 5-[(N-Methoxyethyl-N-methoxyethoxyethyl)amino methyl]thieno[2,3-b]thiophene-2-sulfonamide (6.42 g., 15.71 mmole) from Step A was dissolved in i-propanol (550 mL) filtered and methanolic HCl (5.54 M)(3.00 mL; 16.6 mmole) was added. The resulting mixture was swirled, allowed to stand for 15 minutes, and was boiled down to 200 mL and seeded. On cooling most of the product oiled out. A crust of crystals formed and this was broken up by trituration to provide 5.64 g of pure 5-[(N-Methoxyethyl-N-methoxyethoxyethyl)aminomethyl]-thieno[2,3-b]thiophen-2-sulfonamide hydrochloride, m.p. 147°-148°C. The novel compound, phosphate buffer salts, and benzalkonium chloride are added to and dissolved in water. The pH of the composition is adjusted to 5.4-7.4 and diluted to volume. The composition is rendered sterile by ionizing radiation. The compound and the petrolatum are aseptically combined. Ophthalmic inserts are manufactured from compression molded films which are prepared on a Carver Press by subjecting the powdered mixture of the above ingredients to a compressional force of 12,000 lbs. (gauge) at 300°F for one to four minutes. The film is cooled under pressure by having cold water circulate in the plated. Ophthalmic inserts are then individually cut from the film with a rod-shaped punch. Each insert is placed into a vial, which is then placed in a humidity cabinet (88% R.H. at 30°C) for two to four days. After removal from the humidity cabinet, the vials are stoppered and then capped. The vials containing the hydrate insert are then autoclaved at 250°F for ½ hour.

Claims: 1. 5-[N-Methoxyethyl-N-methoxyethoxyethyl) aminomethyl]thieno[2,3-b]thiophene-2-sulfonamide. 2. An ophthalmological formulation for the treatment of ocular hypertension and glaucoma comprising an ophthalmologically acceptable carrier and an effective ocular antihypertensive amount of the compound of Claim 1. 3. The use of the compound as claimed in Claim 1 for the preparation of a medicament useful for treating ocular hypertension and glaucoma.

Inventors: HARTMAN, GEORGE D., PRUGH, JOHN D.
Applicants: MERCK & CO. INC.
Application year: 1989
Main classification: C07D495
IPC codes: A61P27, C07D495, A61P9, A61K31