Pyrido[2,3-d]pyrimidine derivatives

Abstract: The present invention relates to a novel pyrido[2,3-­ d]pyrimidine derivative having the formula (I): wherein each of R₁ and R₂, which may be the same or different, is a lower alkyl group; and each of R₃ and R₄, which may be the same or different, is hydrogen, halogen, hydroxy, nitro, amino, hydroxyamino, hydrazi­ no, azido, a lower alkenylamino group or a lower alkylamino group which may optionally be substituted by hydroxy; and pharmaceutically acceptable salt thereof. These com­ pounds are useful as anti-allergic agents, for example, for the treatment of bronchial asthma, urticaria, allergic rhinitis, allergic dermatoses or allergic conjunctivitis.

Description: The present invention relates to novel pyrido[2,3-d]pyrimidine derivatives, pharmaceutically acceptable salts thereof, a process for preparing them and pharmaceutical compositions containing them as an active ingredient. It is known that the so-called "chemical mediator", i.e. histamine, serotonin or SRS-A, plays an important role in the appearance of various allergic symptoms in the human body. A pharmaceutical which antagonizes such biochemical substances and/or inhibits their release would be useful for treating or preventing allergic diseases. There have been several prior attempts to synthesize such compounds. It has now been found that certain pyrido[2,3-d]pyrimidine derivatives have good anti-allergic activity. Chemical Abstracts, vol. 100, no. 9, 68254z describes compounds of formula I (hereafter) in which R₁ is methyl or ethyl and the remainder unsubstituted. Chemical Abstracts, vol. 93, no. 9, 95234 describes compounds of formula I in which R₁ is ethyl and R₂ propyl or butyl, the remainder being unsubstituted. Chemical Abstracts, vol. 102, no. 15, 131985x describes compounds of formula I in which R₁ and R₂ are methyl, the remainder being unsubstituted. Chemical and Pharmaceutical Bulletin, vol. 33, no.4 (1985) pp 1375-1379 describes compounds of formula I in which R₁ and R₂ are both methyl or ethyl, the remainder being unsubstituted. DE-A-2317230 describes compounds of formula I in which R₁ and R₂ are methyl and the 7- position occupied by amino, the remainder being unsubstituted. No pharmaceutical use is described in the above. US-A-3272816 describes compounds of formula I in which R₁ and R₂ are: (i) ethyl and the 7- position occupied by amino, (ii) ethyl and the 7- position occupied by acetamido, (iii) methyl and ethyl and the 7- position occupied by amino, (iv) ethoxy and ethyl or cyanoethoxyethyl and ethyl and the 7-position occupied by amino. These are said to be useful as anti-ulcer agents. According to one aspect the invention provides for the use of pyrido[2,3-d]pyrimidine derivative having the formula (I): wherein each of R₁ and R₂, which may be the same or different, is a C₁₋₅ alkyl group; and each of R₃ and R₄, which may be the same or different, is hydrogen, halogen, hydroxy, nitro, amino, hydroxyamino, hydrazino, azido, a C₂₋₅ alkenylamino group or a C₁₋₅ alkylamino group which may optionally have hydroxy; or pharmaceutically acceptable salt thereof for the manufacture of anti-allergic medicaments. According to another aspect the invention provides a process for preparing a pyrido[2,3-d]pyrimidine derivative of formula (I) as specified above which comprises reacting a compound having the formula (II): wherein R₁ and R₂ are as defined above and, depending on the desired substituents R₃ and R₄, X is hydrogen, methyl or cyanomethyl and Y is amino or dimethylaminomethyleneamino; with (according to the desired substituents R₃ and R₄) dimethylformamide or dimethylformamide dialkylacetal, cyanomethylenetriphenylphosphorane, nitromethane or a base, and if desired, carrying out reduction, halogenation or substitution. According to yet another aspect the invention provides a pyrido[2,3-d]pyrimidine derivative having the following formula (I'): wherein each of R₁ and R₂, which may be the same or different, is a C₁₋₅ alkyl group; R₃' is hydrogen, halogen, hydroxy, nitro, amino, hydroxyamino, hydrazino, azido, a C₂₋₅ alkenylamino group or a C₁₋₅ alkylamino group which may optionally have hydroxy; R₄' is hydrogen or amino; and provided that at least one of R₃' and R₄' is not hydrogen; or pharmaceutically acceptable salt thereof. When, e.g., R₄' is hydrogen, R₃' may be amino and R₂ and R₃ preferably ethyl. Alternatively, R₃' may be hydroxyamino. The C₁₋₅ alkyl groups may be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec -butyl, tert -butyl or pentyl. The halogen may be fluoride, chloride, bromide or iodide, preferably chloride. The alkylamino groups may be straight or branched alkenylamino groups having 2 to 5 carbon atoms, such as vinylamino, propenylamino, isopropenylamino, allylamino, butenylamino or pentenylamino. The alkylamino groups may be straight or branched alkylamino group having 1 to 5 carbon atoms, such as methylamino, ethylamino, propylamino, isopropylamino, butylamino, isobutylamino, sec -butylamino, tert -butylamino or pentylamino, which may optionally be substituted by hydroxy. Preferred compounds of the present invention include: 1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-hydroxy-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-chloro-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-chloro-1,3-diethylpyrido[2,3-d]pyrimidine-2,4-dione 5-chloro-1-isobutyl-3-methylpyrido[2,3-d]pyrimidine-2,4-dione 6-nitro-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-amino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-amino-1,3-diethylpyrido[2,3-d]pyrimidine-2,4-dione 5-amino-1-isobutyl-3-methylpyrido[2,3-d]pyrimidine-2,4-dione 6-amino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 7-amino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 7-amino-5-hydroxy-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-methylamino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-methylamino-1,3-diethylpyrido[2,3-d]pyrimidine-2,4-dione 5-ethylamino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-isobutylamino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5- tert -butylamino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-allylamino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-hydroxyamino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-(2-hydroxyethyl)amino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-hydrazino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-azido-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione 5-azido-1,3-diethylpyrido[2,3-d]pyrimidine-2,4-dione 5-azido-1-isobutyl-3-methylpyrido[2,3-d]pyrimidine-2,4-dione The pyrido[2,3-d]pyrimidine derivatives of the present invention include pharmaceutically acceptable salts of the compounds having formula (I) above, for example, salts with alkali metal such as sodium or potassium, with alkaline-earth metal such as calcium or barium, or with other metals such as aluminum, acid addition salts with an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, or with an organic acid such as formic acid, acetic acid, citric acid or lactic acid; or salts with an organic base such as ammonia or the like. These salts can be prepared from pyrido[2,3-d]pyrimidine derivatives or other salts of these derivatives by conventional methods. When optical isomers of the compounds of the invention occur, the present invention includes any of the dl , d and l -isomers. By using uracil derivatives having the formula (II): wherein each of R₁ and R₂ has the same meaning as in the formula (I); X is hydrogen, methyl or cyanomethyl; and Y is amino or dimethylaminomethyleneamino; as a starting material, the compounds of the present invention can be prepared as follows. (1) when X is methyl and Y is amino in the formula (II), the compounds of the formula (II) and dimethylformamide (DMF) are reacted with a phosphorus oxyhalide such as phosphorus oxychloride, a thionyl halide such as thionyl chloride or a triphenylphosphine dihalide such as triphenylphosphine dichloride or triphenylphosphine dibromide at room temperature or at a suitable temperature above room temperature for several hours to give the compounds of the present invention having halogen such as fluorine, chlorine, bromine or iodine at 5-position. Further, the said compounds having halogen at 5-position are reacted with ammonia, hydroxyamine, hydrazine, sodium azide ,a straight or branched alkenylamino group having 2 to 5 carbon atoms, such as vinylamine, propenylamine, isopropenylamine, allylamine, butenylamine or pentenylamine, or a straight or branched alkylamino group having 1 to 5 carbon atoms such as methylamine, ethylamine, propylamine, isopropylamine, butylamine, isobutylamine, sec -butylamine, tert -butylamine or pentylamine, which may optionally have hydroxy, to introduce a substituent which is amino, a straight or branched alkylamino groups having 1 to 5 carbon atoms such as methylamino, ethylamino, propylamino, isopropylamino, butylamino, isobutylamino, sec -butylamino, tert -butylamino or pentylamino, a straight or branched alkenylamino group having 2 to 5 carbon atoms, such as vinylamino, propenylamino, isopropenylamino, allylamino, butenylamino or pentenylamino, hydroxyamino, hydrazino or azido, in substitution for halogen at 5-position. The above reaction is carried out in an appropriate solvent, e.g. an alcohol such as methanol or ethanol, or DMF, at room temperature, at a suitable temperature above room temperature or under reflux, for several hours. When a substance having low boiling point such as ammonia is used, a sealed tube can be employed. The compounds of the present invention having halogen or azido at 5-position prepared as mentioned above can be reduced to give compounds of the invention having hydrogen or amino at 5-position by a known method such as catalytic reduction using palladium-carbon (Pd-C). The compounds of the formula (II), wherein X is methyl and Y is amino, is reacted with dimethylformamide dialkylacetal, e.g. dimethylformamide dimethylacetal, dimethylformamide diethylacetal, dimethylformamide dibutylacetal and the like in an appropriate solvent such as DMF at room temperature or at a suitable temperature above room temperature for several hours to give the compounds of the present invention having a hydroxy group at the 5-position. The said compounds having halogen at the 5-position can be prepared by reacting a compound having a hydroxy group at the 5-position with a halogenating agent such as oxyphosphorus halide, thionyl halide or triphenylphosphine dihalide as mentioned above. (2) When X is hydrogen and Y is amino in the formula (II), the compounds of the formula (II) are reacted with cyanomethylenetriphenylphosphorane to give the compounds of the present invention having amino at 7-position. The said preparation according to the Wittig reaction can be carried out by heating under reflux in dried acetonitrile for several hours in a stream of inert gas such as argon. (3) The compounds of the formula (II), wherein X is hydrogen and Y is dimethylaminomethyleneamino, is reacted with nitromethane in the presence of a base such as triethylamine at room temperature or at a suitable temperature above room temperature for several hours to give the compounds of the present invention having nitro at the 6-position. Further, the resulting compounds are reduced to give the compounds of the invention having amino at the 6-position by a known method such as catalytic reduction using Pd-C. (4) When X is cyanomethyl and Y is amino in the formula (II), the compounds of the formula (II) are reacted with a base such as sodium carbonate at room temperature, at a suitable temperature above room temperature or under reflux for several hours to give the compound having both hydroxy at 5-position and amino at 7-position. The resulting compounds of the present invention can be purified by known methods such as distillation chromatography and recrystallization. Identification is established through, inter alia , elemental analysis, melting point, IR, NMR, UV, mass spectrum, etc. The following examples describe the preparation of certain preferred compounds in accordance with the invention. Example 1. (1) 5.92 g of 5-acetyl-6-amino-1,3-dimethyluracil and 7.34 g of phosphorus oxychloride were added to 100 ml of DMF. The solution was heated for 2 hr at 60 °C and the solvent was distilled off under reduced pressure. After adding water to the residue, the resulting crude crystals were separated from the solution by filtration and recrystallized from ethyl acetate to give 5.34 g of 5-chloro-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 1). Yield: 79 % m.p.: 175 - 177 °C Elementary Analysis: C₉H₈ClN₃O₂ C % H % N % Calculated 47.91 3.57 18.62 Found 48.07 3.56 18.52 NMR(DMSO-d₆): δ=3.38(3H,s), 3.55(3H,s), 7.40(1H,d,J=5Hz), 8.55(1H,d,J=5Hz) In the same manner, 5-chloro-1,3-diethylpyrido[2,3-d]pyrimidine-2,4-dione and 5-chloro-1-isobutyl-3-methylpyrido[2,3-d]pyrimidine-2,4-dione were obtained. (2) 0.34 g of Compound 1 was dissolved in 100 ml of methanol and reduced in the presence of Pd-C. Activated charcoal powder was added, and the solution was heated and filtered. The filtrate was distilled under reduced pressure and ethanol was added thereto. The resulting crude crystals were separated from the solution by filtration and recrystallized from ethanol to give 0.24 g of 1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 2). Yield: 84 % m.p.: 160 - 161 °C Elementary Analysis: C₉H₉N₃O₂ C % H % N % Calculated 56.54 4.75 21.98 Found 56.53 4.78 21.98 NMR(DMSO-d₆): δ=3.30(3H,s), 3.55(3H,s), 7.32(1H,dd,J=5Hz,7.5Hz), 8.35(1H,dd,J=2.5Hz,7.5Hz), 8.68(1H,dd,J=2.5Hz,5Hz) Example 2. (1) 1.35 g of Compound 1 was dissolved in 10 ml of DMF and 0.52 g of 90 % sodium azide was added thereto. The solution was stirred for 6 hr at room temperature and the solvent was distilled off under reduced pressure. After adding water, the resulting crystals were separated by filtration to give 1.16 g of 5-azido-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 3) Yield: 83 % m.p.: 102 - 108 °C (decomposition) IR(KBr): ν max =2110 (N₃) In the same manner, 5-azido-1,3-diethylpyrido[2,3-d]pyrimidine-2,4-dione and 5-azido-1-isobutyl-3-methylpyrido[2,3-d]pyrimidine-2,4-dione were obtained. (2) 1.33 g of Compound 3 was dissolved in 400 ml of methanol and reduced in the presence of 300 mg of Pd-C. Activated charcoal powder was added, and the solution was heated and filtered. The filtrate was distilled under reduced pressure and ethanol added thereto. The resulting crude crystals were separated by filtration and recrystallized from ethanol to give 0.87 g of 5-amino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 4). Yield: 74 % m.p.: 233 - 235 °C Elementary Analysis: C₉H₁₀N₄O₂ C % H % N % Calculated 52.42 4.89 27.17 Found 52.66 4.87 26.89 NMR(DMSO-d₆): δ=3.20(3H,s), 3.40(3H,s), 6.40(1H,d,J=6Hz), 7.90(1H,d,J=6Hz), 7.90(2H,br) In the same manner, the following compounds were obtained. 5-amino-1,3-diethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 5) Yield: 64.8 % m.p.: 216 - 217 °C Elementary Analysis: C₁₁H₁₄N₄O₂ C % H % N % Calculated 56.40 6.02 23.92 Found 56.54 5.99 23.86 NMR(CDCl₃): δ=1.29(3H,t,J=6Hz), 1.30(3H,t,J=6Hz), 4.12(2H,q,J=7Hz), 4.38(2H,q,J=7Hz), 6.31(1H,d,J=6Hz), 7.90(1H,br), 8.08(1H,d,J=6Hz) 5-amino-1-isobutyl-3-methylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 6) Yield: 67 % m.p.: 183 - 185 °C Elementary Analysis: C₁₂H₁₆N₄O₂·4/25H₂O C % H % N % Calculated 57.39 6.55 22.31 Found 57.76 6.47 22.04 NMR(DMSO-d₆): δ=0.87(6H,d,J=6Hz), 2.0-2.5(1H,m), 3.29(3H,s), 4.08(2H,d,J=6Hz), 6.51(1H,d,J=6Hz), 7.90(1H,br), 8.04(1H,d,J=6Hz) Example 3. (1) 0.4 g of Compound 1 and 1.86 g of methylamine (30 % methanol solution) were added to 10 ml of DMF. The solution was stirred for 2 hours at room temperature and the solvent was distilled off under reduced pressure. After adding water, the resulting crude crystals were separated by filtration and recrystallized from ethyl acetate to give 0.23 g of 5-methylamino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 7) Yield: 63 % m.p.: 179 - 180 °C Elementary Analysis: C₁₀H₁₂N₄O₂ C % H % N % Calculated 54.54 5.49 25.44 Found 54.40 5.48 25.21 NMR(DMSO-d₆): δ=2.85(3H,d,J=5Hz), 3.19(3H,s), 3.40(3H,s), 6.35(1H,d,J=6Hz), 8.05(1H,d,J=6Hz), 8.90(1H,br) In the same manner, 5-methylamino-1,3-diethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 8) was obtained. Yield: 52 % m.p.: 114 °C Elementary Analysis: C₁₂H₁₆N₄O₂·2/5H₂O C % H % N % Calculated 56.41 6.63 21.93 Found 56.15 6.42 21.90 NMR(CDCl₃): δ=1.25(3H,t,J=7Hz), 1.29(3H,t,J=7Hz), 4.10(2H,q,J=6Hz), 4.38(2H,q,J=6Hz), 6.29(1H,d,J=6Hz), 8.15(1H,d,J=6Hz), 9.22(1H,br) (2) Using allylamine or isopropylamine instead of methylamine, the following compounds were obtained. 5-allylamino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 9) Yield: 72 % m.p.: 120 - 121 °C Elementary Analysis: C₁₂H₁₄N₄O₂ C % H % N % Calculated 58.52 5.73 22.75 Found 58.28 5.78 22.60 NMR(CDCl₃): δ=3.40(3H,s), 3.64(3H,s), 3.93(2H,m), 4.25(2H,m), 5.80(1H,m), 6.30(1H,d,J=7Hz), 8.10(1H,d,J=7Hz), 9.38(1H,br) 5-isopropylamino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (compound 10) Yield: 77.9 % m.p.: 127 - 128 °C Elementary Analysis: C₁₂H₁₆N₄O₃ C % H % N % Calculated 58.05 6.50 22.57 Found 58.13 6.68 22.58 NMR(DMSO-d₆): δ=1.23(6H,d,J=6Hz), 3.23(3H,s), 3.46(3H,s), 3.82(1H,m), 6.49(1H,d,J=6Hz), 8.05(1H,d,J=6Hz), 9.07(1H,d,J=8Hz) Likewise, using appropriate alkylamines, the corresponding 5-ethylamino-, 5-isobutylamino- and 5- tert -butylamino- compounds were obtained. (3) In the same manner, using hydroxylamine hydrochloride instead of methylamine, 5-hydroxyamino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 11) was obtained. Yield: 84 % m.p.: 118 - 120 °C Elementary Analysis: C₉H₁₀N₄O₃ C % H % N % Calculated 48.65 4.54 25.21 Found 48.85 4.45 25.34 NMR(CDCl₃, DMSO-d₆): δ=3.39(3H,s), 3.62(3H,s), 6.85(1H,d,J=6Hz), 8.15(1H,d,J=6Hz), 9.29(1H,s), 10.55(1H,br) (4) In the same manner, using hydrazine hydrate instead of methylamine, 5-hydrazino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 12) was obtained. Yield: 90 % m.p.: 191 - 192 °C Elementary Analysis: C₉H₁₁N₅O₂ C % H % N % Calculated 48.86 5.01 31.66 Found 49.12 5.05 31.60 NMR(DMSO-d₆): δ=3.24(3H,s), 3.48(3H,s), 4.72(2H,brs), 6.94(1H,d,J=6Hz), 8.12(1H,d,J=6Hz), 9.84(1H,brs) (5) In the same manner, using ethanolamine hydrochloride instead of methylamine, 5-(2-hydroxyethyl)amino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (compound 13) was obtained. Yield: 68.8 % m.p.: 163 °C IR(KBr): 3300, 1685, 1645, 1590, 1570 cm⁻¹ NMR(DMSO-d₆): δ=3.25(3H,s), 3.48(3H,s), 3.62(2H,ddd,J=6Hz), 4.95(2H,t,J=5Hz), 6.48(1H,d,J=6Hz), 8.05(1H,d,J=6Hz), 9.26(1H,t,J=5Hz) Example 4. 0.8 g of 5-acetyl-6-amino-1,3-dimethyluracil was dissolved in DMF and 4 ml of dimethylformamide dibutylacetal was added thereto. The solution was heated for 8 hr at 80 °C and distilled under reduced pressure. After purification by silica gel column chromatography, the crude product was recrystallized from ethanol to give 0.59 g of 5-hydroxy-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 14). Yield: 70.2 % m.p.: 162 - 163 °C Elementary Analysis: C₉H₉N₃O₃ C % H % N % Calculated 52.17 4.38 20.28 Found 52.31 4.29 20.32 NMR(DMSO-d₆): δ=3.30(3H,s), 3.55(3H,s), 6.78(1H,d,J=6Hz), 8.42(1H,d,J=6Hz), 12.30(1H,br) Example 5. 0.18 g of 6-amino-5-formyl-1,3-dimethyluracil and 0.45 g of cyanomethylenetriphenylphosphorane were added to 20 ml of dried acetonitrile. The solution was heated under reflux for 12 hr in a stream of argon. After cooling, the precipitated crystal was separated by filtration to give 0.08 g of 7-amino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 15). Yield: 39 % m.p.: 290 - 295 °C Elementary Analysis: C₉H₁₀N₄O₂ C % H % N % Calculated 52.42 4.89 27.14 Found 52.50 4.97 27.02 NMR(CF₃COOH): δ=3.57(3H,s), 3.84(3H,s), 3.84(3H,s), 6.93(1H,d), 8.52(1H,d) Example 6. (1) 0.24 g of 5-formyl-6-dimethylaminomethyleneamino-1,3-dimethyluracil and 0.5 g of triethylamine were added to 10 ml of nitromethane, and the mixture was heated for 2.5 hr at 80 °C. After the solvent was distilled off under reduced pressure, ether was added to the residue. The resulting crude crystals were separated by filtration and recrystallized from ether to give 0.14 g of 6-nitro-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 16). Yield: 58.8 % m.p.: 203 - 205 °C Elementary Analysis: C₉H₈N₄O₄ C % H % N % Calculated 45.76 3.41 23.72 Found 45.82 3.43 23.85 NMR(DMSO-d₆): δ=3.63(3H,s), 3.81(3H,s), 8.61(1H,d,J=3Hz), 9.43(1H,d,J=3Hz) (2) 0.08 g of Compound 16 was dissolved in methanol and reduced in the presence of 100 mg of Pd-C. Activated charcoal powder was added, and the solution was heated and filtered. The filtrate was distilled under reduced pressure and the residue was recrystallized from methanol to give 0.05 g of 6-amino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 17). Yield: 71.6 % m.p.: 219 - 220 °C NMR(DMSO-d₆): δ=3.30(3H,s), 3.50(3H,s), 5.50(2H,s), 7.60(1H,d,J=3Hz), 8.17(1H,d,J=3Hz) Example 7. 1.21 g of 6-amino-5-(2-cyanoacetyl)-1,3-dimethyluracil and 2.90 g of sodium carbonate were added to 20 ml of water, and the solution was heated under reflux for 1 hr. After cooling, the precipitate was separated from the solution by filtration to give 1.09 g of 7-amino-5-hydroxy-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 18). Yield: 91 % m.p.: >300 °C Elementary Analysis: C₉H₁₀N₄O₃ C % H % N % Calculated 48.65 4.54 25.22 Found 48.37 4.48 25.09 NMR(CF₃COOH): δ=3.52(3H,s), 3.81(3H,s), 6.20(1H,s) Example 8. In the same manner as Example 3, the following compounds were obtained. 5- tert -butylamino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 19) m.p.: 154 °C 5-(2-hydroxyethyl)amino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione (Compound 20) m.p.: 152 - 154 °C Pharmaceutical studies on the compounds of the present invention are now described below. (1) Acute toxicity test The test compounds were orally administered to groups of 5 ICR-strain male mice. LD₅₀ value of the compound of the present invention was calculated by the Litchfield-Wilcoxon's method based on mortality for 14 days after drug administration. An example of the results is shown in Table 1. Test compound LD₅₀ (mg/kg) Compound 4 850 Compound 5 >1,000 Compound 7 1,050 Compound 9 >1,000 Compound 10 850 Compound 11 >1,000 Compound 15 >1,200 Theophylline 417 (2) Anti-allergic effect PCA (Passive Cutaneous Anaphylaxis) reaction in rats was taken as an index of the anti-allergic effect of the compound of the present invention. In order to perform sensitization, anti-DNP-Asc (dinitrophenylated Ascaris extracts) serum diluted with saline was injected intradermally at 4 sites on the shaved back of groups of 6 Wister-strain male rats (6 weeks of age). 1 hour after oral administration of the test drug, the mixture of equivalent amount of DNP-Asc (5 mg/ml) and 2% Evans blue were intravenously injected to generate PCA reaction. 30 minutes thereafter, rats were killed by decapitation and exsanguinated. The skin was opened in order to evaluate the leakage of blue dye. The obtained skin was dissolved in 2N potassium hydroxide, then 2N phosphoric acid and acetone were added thereto. The amount of dye was determined by measurement of absorbance at 620 nm after centrifugation. An example of the results is shown in Table 2. Test compound Dosage (mg/kg) Inhibition (%) control - 0 Compound 2 20 51.2 Compound 4 20 68.7 Compound 5 20 79.2 Compound 7 20 73.7 Compound 8 20 76.4 Compound 9 20 67.9 Compound 10 20 86.6 Compound 11 20 74.0 Compound 14 20 49.9 Compound 15 20 68.7 Compound 17 20 56.2 Theophylline 20 57.9 As is clearly apparent from the above mentioned results, the pyrido[2,3-d]pyrimidine derivatives of the present invention have excellent anti-allergic properties which are superior to those of conventional pharmaceuticals, for example, theophilline. Furthermore, the compounds of the invention possess low toxicity, so that they have good safety properties. They are useful in the prevention or treatment of various allergic diseases, such as bronchial asthma, urticaria, allergic rhinitis, allergic dermatoses or allergic conjunctivitis In addition, since the compounds of the present invention can be administered orally, they can be used in the treatment of chronic diseases. As another index of anti-allergic effect of the compound of the present invention different from the PCA reaction, the phosphodiesterase (PDE) inhibiting effect was tested. As may be seen from the results, the compounds of the present invention effectively inhibited PDE activity even at very low concentrations. The compounds of the present invention have excellent PDE inhibiting effect, so that they are not only useful as anti-allergic agents, but also as cardiotonics, bronchodilators and the like. The compounds of the present invention can be made up into pharmaceutical compositions by combination with appropriate medicial carriers or diluents, and can be formulated into preparations in solid, semisolid, liquid or gaseous form such as tablets, capsules, powders, granules, ointments, solutions, suppositories, injections, inhalants, aerosols and cataplasms in usual ways for oral or parenteral administrations. In pharmaceutical dosage forms, the compounds of the present invention can be used in the form of their pharmaceutically acceptable salts, and also can be used alone or in appropriate association, as well as in combination with other pharmaceutically active components such as a bronchodilator, artihistaminic or tranquilizer. In case of oral preparations, the compounds can be used alone or combined with appropriate additives to make tablets, powders, granules or capsules, e.g. with conventional additives such as lactose, mannitol, corn starch or potato starch; with binders such as crystalline cellulose, cellulose derivatives, acacia, corn starch or gelatins; with disintegrators such as corn starch, potato starch or sodium carboxymethylcellulose; with lubricants such as talc or magnesium stearate; and if desired, with diluents, buffering agents, moistening agents, preservatives and flavoring agents. The compounds of the invention can also be made into an ointment by conbination with an ointment base such as vaseline, paraffin, plastibase, simple ointment, hydrophilic ointment, hydrophilic vaselin or hydrophilic plastibase. Furthermore, the compounds of the invention can be made into a suppository by mixing with a variety of bases, e.g. fatty and oily base such as cacao butter,emulsifying base or water-soluble base such as macrogol. The compounds of the present invention can be formulated into preparations for injections by dissolving, suspending or emulsifying in aqueous or non-aqueous solvent, such as distilled water for injection, physiologically saline solution, vegetable oil, synthetic aliphatic acid glycerides, esters of higher aliphatic acid or propylene glycol. In case of inhalations or aerosol preparations, the compounds of the invention in the form of a liquid or minute powder can be filled into an aerosol container with gas or liquid spraying agent, and if desired, with conventional adjuvants such as humidifying agents or dispersing agent. They can also be used as pharmaceuticals for a non-pressurized preparation such as in a nebulizer or an atomizer. In order to make the compounds of the present invention into collyriums, they can be prepared as a solution or suspension together with an aqueous solvent such as sterile, purified water and physiologically saline solution, or a non-aqueous solvent for injection. Cataplasms can be prepared by mixing the compounds with mentha oil, concentrated glycerin, kaolin or other suitable additives. The desirable dose of the compounds of the present invention varies with the subject, form of the drug, method and period of administration. However, in order to obtain desirable effects, generally it is recommended to administer orally 1 to 1000 mg, preferably 5 to 600 mg daily. Unit preparations are also recommended for administration in one to several units daily. In case of parenteral administrations e.g. injections, doses of the compounds in the order of one tenth to one third of the above dose are preferable as daily doses. Some prescriptions of the pharmaceutical compositions are shown below as examples which contain the compounds of the present invention as active ingredients. Prescription example 1 (tablet) Component Content in a tablet (mg) compound of this invention 100 lactose 130 corn starch 40 magnesium stearate 10 Total 280 mg Prescription example 2 (capsule) Component Content in a capsule (mg) compound of this invention 50 lactose 250 Total 300 mg Prescription example 3 (injection) Component Content in an ampule (mg) compound of this invention 10 sodium chloride proper amount distilled water for injection proper amount Total 1 ml Prescription example 4 (ointment) Component Weight (g) compound of this invention 1 emulsified wax 30 white petrolatum 50 liquid paraffin 20 Total 101 g Prescription example 5 (suppository) Component Content in a suppository (mg) compound of this invention 20 cacao butter 1980 Total 2000 mg Prescription example 6 (inhalation) Component Content in a inhalation (g) compound of this invention 1 lactose 5 Total 6 g

Claims: The use of pyrido[2,3-d]pyrimidine derivatives having the formula (I): wherein each of R₁ and R₂, which may be the same or different, is a C₁₋₅ alkyl group; and each of R₃ and R₄, which may be the same or different, is hydrogen, halogen, hydroxy, nitro, amino, hydroxyamino, hydrazino, azido, a C₂₋₅ alkenylamino group or a C₁₋₅ alkylamino group which may optionally have hydroxy; or pharmaceutically acceptable salts thereof for the manufacture of anti-allergic medicaments. A process for preparing a pyrido[2,3-d]pyrimidine derivative of formula (I) as specified in claim 1 which comprises reacting a compound having the formula (II): wherein R₁ and R₂ are as defined in claim 1 and, depending on the desired substituents R₃ and R₄, X is hydrogen, methyl or cyanomethyl and Y is amino or dimethylaminomethyleneamino; with (according to the desired substituents R₃ and R₄) dimethylformamide or dimethylformamide dialkylacetal, cyanomethylenetriphenylphosphorane, nitromethane or a base, and if desired, carrying out reduction, halogenation or substitution. A pyrido[2,3-d]pyrimidine derivative having the following formula (I'): wherein each of R₁ and R₂, which may be the same or different, is a C₁₋₅ alkyl group; R₃' is hydrogen, halogen, hydroxy, nitro, amino, hydroxyamino, hydrazino, azido, a C₂₋₅ alkenylamino group or a C₁₋₅ alkylamino group which may optionally have hydroxy; R₄' is hydrogen or amino; and provided that at least one of R₃' and R₄' is not hydrogen; or pharmaceutically acceptable salt thereof. A pyrido[2,3-d]pyrimidine derivative according to claim 3, wherein R₄' is hydrogen, or pharmaceutically acceptable salt thereof. A pyrido [2,3-d]pyrimidine derivative according to claim 4, wherein R₃' is amino, or pharmaceutically acceptable salt thereof. A pyrido[2,3-d]pyrimidine derivative according to claim 5, wherein R₁ and R₂ are ethyl, or pharmaceutically acceptable salt thereof. A pyrido[2,3-d]pyrimidine derivative according to claim 4, wherein R₃' is a C₁₋₅ alkylamino group, or pharmaceutically acceptable salt thereof. A pyrido[2,3-d]pyrimidine derivative according to claim 4, wherein R₃' is hydroxyamino, or pharmaceutically acceptable salt thereof. A pyrido[2,3-d]pyrimidine derivative according to claim 3, wherein R₄' is amino, or pharmaceutically acceptable salt thereof.

Inventors: GO, KOUICHIRO C/O INSTITUTE OF BIO-ACTIVE SCIENCE, KITAMURA, NORIHIKO C/O INST. OF BIO-ACTIVE SCIENCE, KURIMOTO, YOSHIYUKI C/O INST. OF BIO-ACTIVE SCIEN.
Applicants: NIPPON ZOKI PHARMACEUTICAL CO. LTD.
Application year: 1987
Main classification: C07D471
IPC codes: C07D471, A61P37, A61K31