ACETAMIDE COMPOUNDS

Abstract: Novel acetamide compounds of the formula, [wherein R₁ and R₂, each independently represents a hydrogen atom, a C₁ to C₆ straight- or branched-­ chain alkyl or alkenyl group, C₃ to C₆ cycloalkyl or cycloalkenyl group or an C₆ to C₁₀ aromatic group or R₁ and R₂ join with each other in combination with the adjacent N and carbon atoms or further with at least one of nitrogen, oxygen and sulfur atoms to represent a 5- or 6-membered heterocyclic ring group: R₃ represents a C₁-C₆ straight- or branched-chain alkyl or alkenyl group, C₃ to C₆ cycloalkyl or cycloalkenyl group, a halogen atom, a C₁-C₆ straight or branched-chain alkoxyl group, or a C₃-C₆ cyclo­ alkoxy or cycloalkenoxy group and n is 0 to 4] and their pharmaceutically acceptable salts are useful in the treatment of ulcers in mammals.

Description: This invention relates to novel acetamide compounds and pharmaceutically acceptable salts thereof. There have been found a number of substances that are effective for the treatment of gastric ulcer and duodenal ulcer. As example of such substances, there may be mentioned cimetidine, gefarnate and omeprazole. Nevertheless, these substances all suffer from disadvantages to be improved in terms of anti-ulcer activity or gastric- secretion suppressing activity. With a specific view to improving these disadvantages, development of new anti- ulcer agents has been under way. The present inventors have carried out intensive investigation in order to improve the conventionally known compounds, and as a result, found that a group of substances having a new structure exhibit potent anti-ulcer activity, which led to the establishment of this invention. This invention is directed to acetamide compounds represented by the formula (I) and pharmaceutically acceptable salts thereof, and also directed to anti-ulcer agents containing the compound or the salt thereof as an active ingredient: [wherein R₁ and R₂ each independently represents a hydrogen atom, a C₁ to C₆ straight- or branched-chain alkyl or alkenyl group, a C₃ to C₆ cycloalkyl or cycloalkenyl group, or an C₆ to C₁₀ aromatic group; or R₁ and R₂ combine with each other in combination with the adjacent N and carbon atoms or further with at least one of nitrogen, oxygen and sulfur atoms to represent a 5- or 6-membered heterocyclic ring group; R₃ represents a C₁ to C₆ straight- or branched-chain alkyl or alkenyl group, a C₃ to C₆ cycloalkyl or cycloalkenyl group, a halogen atom, a C₁ to C₆ straight- or branched-chain alkyloxy group, or a C₃ to C₆ cycloalkyloxy or cycloalkenyloxy group; and n is 0 to 4]. Referring to the definitions of R₁ and R₂ in the formula (I), the C₁ to C₆ straight- or branched-chain alkyl or alkenyl group may be exemplified by methyl, ethyl, propyl, butyl, isopropyl, isobutyl, isopropenyl, 2-butenyl and hexenyl; the C₃ to C₆ cycloalkyl or cycloalkenyl group may be exemplified by cyclopropyl, cyclohexyl, cyclopentyl, cyclopropenyl, cyclobutenyl and cyclohexenyl; and the C₆ to C₁₀ aromatic group may be exemplified by substituted- or unsubstituted-phenyl or naphthyl group. As the substituents there may be exemplified straight- or branched-chain C₁ to C₆ alkyl, alkenyl, alkyloxy or alkenyloxy group, halogen and nitro group. The aromatic group may be mono-, di- or trisubstituted by these substituents. The examples of the aromatic group are 4-methylphenyl, 4-fluorophenyl, 2-methoxyphenyl, 4-methoxyphenyl, 2-chloro-4-methoxyphenyl, 3,4,5-trimethoxyphenyl, 6-methoxynaphthyl, 2-methoxynaphthyl, 6-chloronaphthyl, 2-fluoronaphthyl and 2-bromo-6-methoxynaphthyl. As the 5-membered or 6-membered nitrogen-containing heterocyclic group wherein R₁ and R₂ combine with each other in combination with the adjacent N and carbon atoms or further with at least one of nitrogen, oxygen and sulfur atoms, there may be exemplified piperidino, piperazino, morpholino, thiomorpholino, thiazolyl and imidazolyl. In the definition of R₃, the C₁ to C₆ straight- or branched-chain alkyl or alkenyl group, the C₃ to C₆ cycloalkyl or cycloalkenyl group, the halogen atom, the C₁ to C₆ straight- or branched-chain alkyloxy group, or the C₃ to C₆ cycloalkyloxy or cycloalkenyloxy group may be exemplified by the same examples as the respectively corresponding groups in R₁ and R₂. In the case where n is an integer of not less than 2, a plurality of R₃ may be the same as or different from each other. As the pharmaceutically acceptable salts of compound [I], there may be exemplified salts formed with organic acids, such as acetic acid, maleic acid, fumaric acid, tartaric acid, oxalic acid, methanesulfonic acid and p-toluenesufonic acid; inorganic acid such as hydrochloric acid, hydrobromic acid, sulfuric acid and phosphoric acid; and acidic amino acids, such as glutamic acid. The compound [I] of this invention can be produced, for example, by the steps of the reaction scheme as is illustrated in the following: (wherein R₁, R₂, R₃ and n are as defined above). The reaction of the compound [II] with chloroacetyl chloride [III] proceeds in an inert solvent, such as chloroform, tetrahydrofuran and toluene, in the presence of an organic base, such as triethylamine and pyridine, or an inorganic base, such as anhydrous potassium carbonate, anhydrous potassium hydrogencarbonate, anhydrous sodium carbonate or anhydrous sodium hydrogencarbonate. The reaction is carried out usually at a temperature up to refluxing temperature of the solvent employed, and preferably at a temperature between -10°C to 30°C. By this procedure, the compound [IV] is formed. Then, the compound [IV] is reacted with 4-aminopyridine [V] to give the compound [I]. This reaction is usually carried out in any inert solvent, such as methyl ethyl ketone, chloroform, dimethylformamide or isopropyl alcohol, at a temperature from room temperature to 80°C. For the purpose of removing hydrochloric acid evolved as the reaction proceeds, the reaction may be carried out in the presence of an inorganic base, such as anhydrous potassium carbonate, anhydrous potassium hydrogen carbonate anhydrous sodium carbonate, anhydrous sodium hydrogen carbonate, potassium hydroxide or sodium hydroxide, or an organic base, such as 1,8-diazabicyclo[5,4,0]- undecane, 1,5-diazabicyclo[4,3,0]nonane, or 1,4-diazabicyclo[2,2,2]-octane. However, the reaction proceeds without addition of such base, whereby the objective compound [I] is obtained in the form of its hydrochloride. Instead of the compound (IV), 4-aminopyridine (V) can be reacted with an analogous compound in which another halogen or alkylsulfonyloxy replaces chlorine in Formula IV. As compounds of this invention, there can be mentioned, for example, the following; N-[2-(phenylamino)phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[2-[(4-methylphenyl)amino]phenyl]-2-[4-pyridinyl)amino]acetamide, N-[2-[(4-fluorophenyl)amino]phenyl]-2-[(4-pyridinyl)amino]actamide, N-[2-[(4-methoxyphenyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[2-[(2-methoxyphenyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[2-[(2-chlorophenyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[2-[(phenylmethyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[2-[[(4-methylphenyl)methyl]amino]phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[2-(imidazolin-1-yl)phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[2-[(2,4-dimethoxyphenyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[2-[(3-hydroxy-4-methoxyphenyl)methylamino]phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[3-methoxy-2-[(4-methoxyphenyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[4,5-dimethoxy-2-(phenylamino)phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[2-[(4-methoxyphenyl)amino]-3-methylphenyl]-2-[(4-pyridinyl)amino]acetamide, N-[3-fluoro-2-[(4-methoxyphenyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[3-chloro-2-(phenylamino)phenyl]-2-[(4-pyridinyl)amino]acetamide, N-[2-(morpholin-1-yl)phenyl]-2-[(4-pyridinyl)amino]acetamide, 2-(4-pyridinyl)amino-N-[2-(thiomorpholin-1-yl)phenyl]acetamide, 2-(4-pyridinyl)amino-N-[2-(pyrrolidin-1-yl)phenyl]acetamide, 2-(4-pyridinyl)amino-N-[2-(pyrrol-1-yl)phenyl]acetamide, N-[2-(piperidin-1-yl)phenyl]-2-[(4-pyridinyl)amino]acetamide, and N-[2-(isoindolin-1-yl)phenyl]-2-[(4-pyridinyl)amino]acetamide. The compounds as disclosed in this invention can be administered orally in the forms of tablets, capsules, granules and powders, and parenterally in the forms of injections and suppositories. The above pharmaceutical preparations may incorporate normally employed additives, such as auxiliary agents, stabilizers, wetting agents, emulsifying agents and buffer solutions, if necessary. The compounds of this invention are normally administered orally in a dose of 10 mg to 1 g per day, but the dosage amount can be varied according to the treatment and is not limited to the above range. Described below are examples and a reference example to explain this invention further in detail, however, these examples do not limit this invention. Reference Example 1 Synthesis of 2-chloro-N-[2-(phenylamino)phenyl]acetamide: In 100 ml of chloroform, 10.4 g of N-phenyl-1,2-benzenediamine and 12.1 g of triethylamine were dissolved, and the mixture was cooled to -5°C to 0°C, and then 13.6 g of chloroacetyl chloride was added dropwise thereto, holding the temperature of the mixture at not higher than 20°C. The reaction nearly went to completion when the addition was finished. After stirring for further 30 minutes, the reaction mixture was diluted with 50 ml of water. The organic layer was separated, washed with water, dried over anhydrous magnesium sulfate and then the solvent is evaporated under reduced pressure. The resulting solid was recrystallized from ethanol to give 15.6 g of crystals having a melting point of 112°C to 113°C. Yield: 60.0 %. Example 1 Synthesis of N-[2-(phenylamino)phenyl]-2-[(4-pyridinyl)-amino]acetamide hydrochloride: In 75 ml of methyl ethyl ketone, 15.6 g of 2-chloro-N-[2-(phenylamino)phenyl]acetamide obtained in Reference Example 1 was added. After adding 5.64 g of 4-aminopyridine thereto, the mixture was heated at 80°C under stirring, whereby crystals separated out according as the reaction proceeded. The reaction continued for 1 hour. The reaction mixture was stirred for a further 2 hours, maintaining the temperature of the mixture at around 10°C, and the crystals separated out were collected by filtration to give 19.7 g of N-[2-(phenylamino)phenyl]-2-[4-pyridinyl)-amino]acetamide hydrochloride. Yield: 92.5 %. IR (KBr, cm⁻¹): 3350, 1690, 1165, 1550, 1530, 1510. NMR (DMSO-d₆, ppm): 5.19(br.s,2H), 6.64-7.40(m,10H), 7.50((m,1H), 8.04(m,3H), 8.32(br.,1H), 10.34(s,1H). Example 2 Synthesis of N-[2-[(4-methylphenyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide hydrochloride: 2-Chloro-N-[2-[(4-methylphenyl)amino]phenyl]acetamide which had been synthesized from N-(4-methylphenyl)-1,2-benzenediamine by substantially the same manner as described in Reference Example 1 and 4-aminopyridine were dissolved in chloroform and the solution was left on standing under stirring at room temperature overnight, whereby the reaction was completed. The resulting precipitates were collected by filtration and recrystallized from ethanol to give N-[2-[(4-methylphenyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide hydrochloride. Melting point, 232° C to 238° C. IR (KBr, cm⁻¹): 3350, 3240, 1685, 1665, 1600, 1545, 1510. NMR (DMSO-d₆, ppm): 2.20(s,3H), 5.18(s,2H), 6.64-7.28(m,8H), 7.44(d,1H), 7.78(s,1H), 8.05(d,2H), 8.30(br.,2H), 10.30(s,1H). Example 3 Synthesis of N-[2-[(4-fluorophenyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide hydrochloride: 2-Chloro-N-[2-[(4-fluorophenyl)amino]phenyl]acetamide which had been synthesized from N-(4-fluorophenyl)-1,2-benzenediamine and chloroacetyl chloride by substantially the same manner as described in Reference example 1 and 4-aminopyridine were dissolved in N,N-dimethylformamide, and the solution was left on standing under stirring at room temperature overnight, whereby the reaction was completed. After the reaction mixture was left standing under cooling at around 10° C, the resulting precipitates were collected by filtration and recrystallized from ethanol to give N-[2-[(4-fluorophenyl)amino]methyl]-2-[(4-pyridinyl)amino]acetamide hydrochloride. Melting point, 239° C to 246° C IR (KBr, cm⁻¹): 3345, 3240, 1685, 1665, 1605, 1595, 1550, 1525, 1500. NMR (DMSO-d₆, ppm): 5.18(s,2H), 6.60-7.20(m,3H), 7.46(d,1H), 7.92(s,1H). Example 4 The compound of Example 1 was subjected to the determination of pharmacological activities by means of the procedure to be described in the below: Water-immersion stress ulceration method Male Slc:SD rats (7-weeks aged: divided in groups each consisting of 6 to 8 animals), after being fasted for 24 hours, were placed in stress cages and immersed in water at 23° C up to the xyphoid process, After stress loading for 7 hours, the rats were killed through exsanguination, and the stomachs were removed, perfused in the inside with 10 ml of 2% formalin and then immersed in the same solution for 10 minutes for fixation. The stomachs were incised along the greater curvature, and the ulcers thus induced were measured for length under the stereoscopic microscope (magnification, x 10), whereby the total sum of the lengths was taken as an ulcer index (U.I., in mm). The test substance was given orally to rats in the form of a 4% gum arabic suspension 30 minutes before stress loading. The results are shown in Table 1. Acute toxicity : A group of five male ddY mice (4-weeks aged) was used for testing. The compound of Example 1 was suspended in 4% gum arabic solution to prepare a test pharmaceutical, which was given orally to each test animals once. The test animals were observed for 7 days, and the LD₅₀ values were calculated to determine the acute toxicity. The results are shown in Table 2. Treatment Dose mg/kg Mean ± S.E. Inhibition rate, % Non-treated control 13.4 ± 2.71 Test substance 10 13.0 ± 4.47 2.8 30 3.8 ± 1.66 71.3 100 1.5 ± 1.31 88.8 Control reference 30 5.2 ± 3.40 61.4 Test substance LD₅₀ value Compound of Example 1 Not less than 2000 mg/kg As may be evident from the above toxicity test results, the compounds of this invention exhibit an extremely low degree of acute toxicity, and are adequately suitable for the use as a drug.

Claims: A compound of the formula: [wherein R₁ and R₂, each independently represents a hydrogen atom, a C₁ to C₆ straight- or branched-chain alkyl or alkenyl group, C₃ to C₆ cycloalkyl or cycloalkenyl group or an C₆ to C₁₀ aromatic group; or R₁ and R₂ join with each other in combination with the adjacent N and carbon atoms or further with at least one of nitrogen, oxygen and sulfur atoms to represent a 5- or 6-membered heterocyclic ring group: R₃ represents a C₁ to C₆ straight- or branched-chain alkyl or alkenyl group, C₃ to C₆ cycloalkyl or cycloalkenyl group, a halogen atom, a C₁ to C₆ straight- or branched-chain alkoxyl group, or a C₃ to C₆ cycloalkoxy or cycloalkenoxy group and n is 0 to 4] or a pharmaceutically acceptable salt thereof. A compound as claimed in Claim 1, wherein R₁ is hydrogen and R₂ is phenyl optionally substituted with C₁ to C₄ alkyl or halogen. A compound as claimed in any one of the preceding claims, wherein n is 0. A compound as claimed in Claim 1, which is selected from N-[2-[(4-methylphenyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide and N-[2-[(4-fluorophenyl)amino]phenyl]-2-[(4-pyridinyl)amino]acetamide. The compound as claimed in Claim 1, which is N-[2-(phenylamino)phenyl]-2-[(4-pyridinyl)amino]acetamide. A pharmaceutical composition comprising a therapeutically effective amount of a compound as claimed in any one of the preceding claims in association with a pharmaceutical carrier or diluent. A compound as claimed in any one of Claims 1 to 5 for use in a method of treatment of the human or animal body. The use of a compound as claimed in any one of Claims 1 to 5 in the manufacture of a medicament for the treatment of ulcers. A process for producing an acetamide compound according to Claim 1, which comprises reacting a N-(2-(substituted-amino)phenyl)carboxylic acid amide of the formula, wherein R₁, R₂, R₃ and n are as defined in Claim 1 and Y is halogen or an alkylsulfonyloxy group, with 4-aminopyridine. A process as claimed in Claim 9, wherein the acid amide is prepared by reacting a 2-(substituted amino)-aniline compound of the formula, wherein R₁, R₂, R₃ and n are as defined in Claim 9, with a reactive derivative of a carboxylic acid of the formula, YCH₂COOH (III) wherein Y is as defined in Claim 9.

Inventors: IBATA, KATSUHIRO 307 SHIN-ISHIKIRI-GURANDOHAITSU, MITSUMORI, NAOMICHI, NISHIMURA, YASUHIRO, OKUNO, SHIRO, SUZUKI, MOTOKO
Applicants: HAMARI YAKUHIN KOGYO KABUSHIKI KAISHA ALSO KNOWN AS HAMARI CHEMICALS, LTD.
Application year: 1989
Main classification: C07D213
IPC codes: C07D213, A61P1, A61K31