Pyrido[4,3-d]pyrimidine derivatives

Abstract: The present invention relates to pyrido[4,3-d]pyrimidine derivatives having the formula (I): wherein each of R₁ and R₂, which may be the same or different, is a lower alkyl group; R₃ is hydrogen, halogen, hydroxy, amino, hydroxyamino, imino, hydrazino or a lower alkylamino group which may optionally be substi­ tuted by hydroxy, amino or a lower alkylamino group; and R₄ is hydrogen, amino, -NH ϑ or a lower alkyl group which may optionally be substituted by hydroxy, amino or a lower alkylamino group; 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[4,3-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[4,3-d]pyrimidine derivatives have good anti-allergic activity. An object of the present invention is to provide novel pyrido[4,3-d]pyrimidine derivatives and pharmaceutically acceptable salts thereof useful for treating or mitigating the effects of allergic diseases as well as possessing low toxicity and fewer side effects and also as intermediates in the preparation of other such compounds. Another object of the invention is to provide a process for preparing these pyrido[4,3-d]pyrimidine derivatives. A further object of the invention is to provide pharmaceutical compositions containing at least one of the pyrido[4,3-d]pyrimidine derivatives or pharmaceutically acceptable salts thereof as an active ingredient. Chemical abstracts 86 , (1977), 121365g; 87 , (1977), 23317u; and 83 , (1975), 193367v describe certain pyrido[4,3-d]pyrimidine derivatives characterised by the presence of a trifluoromethylphenyl group at the 1 position. These are said to have central depressant, analgesic and anti-inflammatory activity but no data is given. The pyrido[4,3-d]pyrimidine derivatives of the present invention are represented by the following formulae (Ia), (Ib) or (Ic): wherein each of R₁ and R₂, which may be the same or different, is an alkyl group having 1 to 5 carbon atoms; R₃ is hydrogen, halogen , hydroxy, amino, hydroxyamino, imino, hydrazino or an alkylamino group having 1 to 5 carbon atoms which may optionally have hydroxy, amino or an alkylamino group having 1 to 3 carbon atoms; and R₄ is amino, -NH ⊖ or an alkyl group having 1 to 5 carbon atoms which may optionally have hydroxy or an alkylamino group having 1 to 3 carbon atoms. Each of R₁ and R₂, which may be the same or different, represents a straight or branched alkyl group having 1 to 5 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec -butyl, tert -butyl or pentyl. R₃ represents hydrogen; halogen, such as fluorine, chlorine, bromine or iodine, preferably chlorine; amino; hydroxyamino; imino; hydrazino; or a 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. The said alkylamino group may optionally have hydroxy, amino or one or two straight or branched alkylamino group having 1 to 3 carbon atoms, such as methylamino, dimethylamino, ethylamino, diethylamino, propylamino or isopropylamino. R₄ represents hydrogen; amino; -NH ⊖ ; or a straight or branched alkyl group having 1 to 5 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec -butyl, tert -butyl or pentyl. The said alkyl group may optionally have hydroxy, amino or one or two straight or branched alkylamino groups having 1 to 3 carbon atoms. R₄ may be e.g. methylamino, dimethylamino, ethylamino, diethylamino, propylamino or isopropylamino. Preferred compounds of the present invention include: 1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione-N6-imide 5-amino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-amino-1,3-diethylpyrido[4,3-d]pyrimidine-2,4-dione 5-amino-1-isobutyl-3-methylpyrido[4,3-d]pyrimidine-2,4-dione 5-methylamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-methylamino-1,3-diethylpyrido[4,3-d]pyrimidine-2,4-dione 5-ethylamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-isopropylamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-hydroxyamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 6-amino-5-imino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 6-butyl-5-imino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 6-(2-hydroxyethyl)-5-imino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-(2-hydroxyethyl)amino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-(2-(N,N-dimethylamino)ethylamino)-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-imino-6-(3-(N,N-diethylamino)propyl)-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-hydroxy-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-cloro-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-hydrazino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione The pyrido[4,3-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[4,3-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 d1 , d and 1 -isomers. The compounds of the present invention can be prepared as follows. The compounds having the general formula (II): wherein each of R₁ and R₂, which may be the same or different, is a lower alkyl group and X is cyano or formyl. are reacted with the compounds having the formula (III): wherein each of Y and Y', which may be the same or different, is hydrogen, hydroxy, amino or a lower alkyl group which may optionally be substituted by hydroxy, amino or a lower alkylamino group. in an appropriate solvent such as dimethylformamide (DMF), pyridine or an alcohol such as methanol, ethanol or isopropyl alcohol at room temperature, at a suitable temperature or under reflux for several tens of minutes to several days to give the compounds of the present invention having the formula (I) above. The compounds of the formula (II) wherein X is cyano are reacted with the compounds of the formula (III) wherein Y and Y' are lower alkyl groups, such as dimethylamine and diethylamine, and then hydrolyzed in water to give the compounds of the present invention having a hydroxy at the 5-position. The said compounds having hydroxy at the 5-position are halogenated by conventional method such as a halogenating reaction using oxyphosphorus chloride to give the compound having halogen at the 5-position. The compounds having amino, hydroxyamino, methylamino, ethylamino or hydrazino at the 5-position can also be prepared by reacting the said compound having halogen at the 5-position with a amine such as ammonia, hydroxyamine, methylamine, ethylamine, hydrazine or the like. 5-Cyano- or 5-formyl-1,3-dimethyl-6-(2-dimethylaminovinyl)uracil, the starting materials, can be obtained by reacting 5-cyano- or 5-formyl-1,3,6-trimethyluracil with dimethylformamide dimethylacetal in an appropriate solvent such as absolute DMF for several tens of minutes to several hours under reflux. The process of the present invention enables the simple production of the novel pyrido[4,3-d]pyrimidine-2,4-dione derivatives of the invention having various substituents at 5- and/or 7-position. The resulting compounds of the present invention can be purified by known methods such as distillation chromatography and recrystallization. Characterisation is established by , inter alia , elemental analysis, melting point, IR, NMR, UV, mass spectrum, etc. The following examples, which are illustrative only and not intended to limit the scope of the invention, describe the preparation of compounds of the present invention. Example 1. (1) 0.47 g of 5-formyl-1,3-dimethyl-6-(2-dimethylaminovinyl)uracil was dissolved in ethanol, and ammonia was added thereto. The solution was stirred for 30 min at room temperature. The precipitated crystals were separated from the solution by filtration and recrystallized from ethanol to give 0.32 g of 1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 1). Yield: 83.8 % m.p.: 174 - 175 °C Elementary Analysis: C₉H₉N₃O₂ C % H % N % Calculated 56.54 4.75 21.98 Found 56.53 4.78 22.00 NMR(DMSO-d₆): δ=3.24(3H,s), 3.42(3H,s), 8.96(1H,d,J=1Hz), 7.40(1H,d,J=6Hz), 8.68(1H,dd,J=1Hz,6Hz) (2) In the same manner, using hydrazine hydrate instead of ammonia, 1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione-N6-imide (Compound 2) was prepared having the following formula. Yield: 78.1 % m.p.: 219 - 220 °C (decomposition) Elementary Analysis: C₉H₁₀N₄O₂·3/20H₂O C % H % N % Calculated 51.74 4.47 26.82 Found 51.95 4.90 26.57 NMR(CF₃COOH): δ=3.60(3H,s), 3.80(3H,s), 7.80(1H,d,J=7Hz), 8.83(1H,dd,J=1Hz,7Hz), 9.51(1H,d,J=1Hz) Example 2. (1) 1.0 g of 5-cyano-1,3-dimethyl-6-(2-dimethylaminovinyl)uracil and 5.0 ml of 30 % ammonia aqueous solution were added to 22.5 ml of DMF. The solution was heated at 100 °C in a sealed tube for 24 hr. The precipitated crystals were separated by filtration, washed with ether and recrystallized from ethanol to give 0.61 g of 5-amino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 3). Yield: 70.0 % m.p.: 229 - 230 °C Elementary Analysis: C₉H₁₀N₄O₂ C % H % N % Calculated 52.42 4.89 27.12 Found 52.60 4.92 27.02 NMR(DMSO-d₆): δ=3.27(3H,s), 3.40(3H,s), 6.45(1H,d,J=7Hz), 6.45(1H,d,J=7Hz), 8.08(1H,d,J=6Hz) In the same manner, the following compounds were obtained. 5-amino-1,3-diethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 4) Yield: 62.7 % m.p.: 181 - 183 °C Elementary Analysis: C₁₁H₁₄N₄O₂ C % H % N % Calculated 56.40 6.02 23.92 Found 56.52 6.02 23.96 NMR(CDCl₃): δ=1.28(3H,t,J=7Hz), 1.31(3H,t,J=7Hz), 4.12(4H,q,J=7Hz), 6.35(1H,d,J=6Hz), 8.16(1H,d,J=6Hz) 5-amino-1-isobutyl-3-methylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 5) Yield: 73.3 % m.p.: 167 °C Elementary Analysis: C₁₂H₁₆N₄O₂ C % H % N % Calculated 58.05 6.50 22.57 Found 58.23 6.51 22.58 NMR(CDCl₃): δ=0.95(6H,d,J=6Hz), 2.20(1H,br), 3.40(3H,s), 3.90(2H,d,J=7Hz), 6.31(1H,d,J=6Hz), 8.15(1H,d,J=6Hz) (2) In the same manner, using methylamine or isopropylamine instead of ammonia, the following compounds were obtained. 5-methylamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 6) Yield: 67.0 % m.p.: 228 - 229 °C Elementary Analysis: C₁₀H₁₂N₄O₂ C % H % N % Calculated 54.54 5.49 25.44 Found 54.79 5.57 25.41 5-methylamino-1,3-diethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 7) Yield: 44.9 % m.p.: 103 - 105 °C Elementary Analysis: C₁₂H₁₆N₄O₂ C % H % N % Calculated 58.05 6.50 22.57 Found 58.14 6.56 22.70 NMR(CDCl₃): δ=1.25(3H,t,J=7Hz), 1.33(3H,t,J=7Hz), 3.09(3H,d,J=5Hz), 4.11(4H,q,J=7Hz), 6.28(1H,d,J=6Hz), 8.25(1H,d,J=6Hz), 9.05(1H,br) 5-isopropylamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 8) Yield: 50 % m.p.: 117 °C Elementary Analysis: C₁₂H₁₆N₄O₂ C % H % N % Calculated 58.05 6.50 22.57 Found 58.26 6.68 22.76 NMR(DMSO-d₆): δ=1.22(6H,d,J=6.5Hz), 3.25(3H,s), 3.40(3H,s), 4.29(1H,m), 6.45(1H,d,J=6Hz), 8.15(1H,d,J=6.0Hz), 8.82(1H,d,J=7.5Hz) (3) In the same manner, using hydroxyamine instead of ammonia, 5-hydroxyamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 9) was obtained. Yield: 88.6 % m.p.: >300 °C Elementary Analysis: C₉H₁₀N₄O₃ C % H % N % Calculated 48.65 4.54 25.22 Found 48.61 4.51 25.13 NMR(CF₃COOH): δ=3.38(3H,s), 3.62(3H,s), 7.57(1H,d,J=7.1Hz), 8.64(1H,d,J=7.1Hz), 9.25(1H,br), 9.55(1H,br) (4) In the same manner, using hydrazine hydrate instead of ammonia, 6-amino-5-imino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 10) was obtained. Yield: 86.8 % m.p.: 258 - 259 °C (decomposition) Elementary Analysis: C₉H₁₁N₅O₂ C % H % N % Calculated 48.86 5.01 31.66 Found 48.69 5.05 31.57 NMR(CF₃COOH): δ=3.53(3H,s), 3.70(3H,s), 6.88(1H,d,J=7Hz), 8.13(1H,br), 8.26(1H,d,J=7Hz) (5) In the same manner, using n-butylamine instead of ammonia, 6-butylamino-5-imino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 11) was obtained. Yield: 93.4 % m.p.: 199 °C Elementary Analysis: C₁₃H₁₈N₄O₂ C % H % N % Calculated 59.52 6.92 21.36 Found 59.54 6.92 21.29 NMR(CDCl₃): δ=0.80-2.00(7H,br), 3.41(3H,s), 3.50(3H,s), 3.97(2H,t,J=7Hz), 5.64(1H,d,J=7Hz), 7.32(1H,d,J=7Hz), 9.58(1H,br) (6) In the same manner, using 2-aminoethanol instead of ammonia, the following compounds were obtained. 6-(2-hydroxyethyl)-5-imino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 12) Reaction: refluxing for 10 hr in methanol Yield: 56 % m.p.: 210 °C (decomposition) Elementary Analysis: C₁₁H₁₄N₄O₃ C % H % N % Calculated 52.79 5.64 22.39 Found 52.91 5.85 22.26 NMR(DMSO-d₆): δ=3.22(3H,s), 3.39(3H,s), 3.64(2H,t,J=5Hz), 3.99(2H,t,J=5Hz), 5.16(1H,bs), 5.90(1H,t,J=7.5Hz), 7.66(1H,d,J=7.5Hz), 9.12(1H,s) 5-(2-hydroxyethyl)amino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 13) Reaction: heating for 20 hr at 100 °C in DMF Yield: 56 % m.p.: >200 °C IR(KBr): 3350, 1710, 1680, 1660, 1530, 1050 cm⁻¹ NMR(DMSO-d₆): δ=3.19(3H,s), 3.43(3H,s), 3.61(2H,t,J=5Hz), 3.94(2H,t,J=5Hz), 4.87(1H,br), 6.36(1H,d,J=7.5Hz), 7.90(1H,d,J=7.5Hz) (7) In the same manner, using 2-dimethylaminoethylamine instead of ammonia, 5-(2-(N,N-dimethylamino)ethylamino)-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 14) was obtained. Reaction: heating at 100 °C for 20 hr in DMF Yield: 36 % m.p.: 179 - 180 °C Elementary Analysis: C₁₃H₁₉N₅O₂ C % H % N % Calculated 56.30 6.91 25.25 Found 56.13 7.14 25.02 NMR(DMSO-d₆): δ=2.17(6H,s), 2.46(2H,t,J=6Hz), 3.25(3H,s), 3.39(3H,s), 3.52(2H,ddd,J=5Hz,6Hz), 6.44(1H,d,J=6Hz), 8.14(1H,d,J=6Hz), 9.01(1H,t,J=5Hz) (8) In the same manner, using 3-diethylaminopropylamine instead of ammonia, 5-imino-6-(3-(N,N-diethylamino)propyl)-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 15) was obtained. Reaction: refluxing for 10 hr in methanol Yield: 43.8 % m.p.: 68 °C IR(KBr): 3300, 1700, 1640, 1580, 1560 cm⁻¹ NMR(DMSO-d₆): δ=0.94(6H,s), 2.46(2H,t,J=6Hz), 3.25(3H,s), 3.39(3H,s), 3.52(2H,ddd,J=5Hz,6Hz), 6.44(1H,d,J=6Hz), 8.14(1H,d,J=6Hz), 9.01(1H,t,J=5Hz) Example 3. (1) 1.85 g of 5-cyano-1,3-dimethyl-6-(2-dimethylaminovinyl)uracil and 1.32 g of dimethylamine hydrochloride were added to 40 ml of pyridine, and the solution was heated under reflux for 12 hr. 1.32 g of dimethylamine hydrochloride was added and the solution was heated under reflux for 36 hr. After the solvent was distilled off, water was added to the residue. The precipitated crystals were separated by filtration and recrystallized from water to give 1.12 g of 5-hydroxy-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 16). Yield: 68 % m.p.: >300 °C Elementary Analysis: C₉H₉N₃O₃·1/2H₂O C % H % N % Calculated 50.00 4.66 19.44 Found 49.91 4.67 19.38 NMR(DMSO-d₆): δ=3.23(3H,s), 3,48(3H,s), 6.41(1H,d,J=8Hz), 7.78(1H,d,J=8Hz), 11.78(1H,brs) (2) 0.72 g of Compound 16 was added to 20 ml of oxyphosphorus chloride and the solution was heated for 8 hr at 80 °C. After the solvent was distilled off, the crude crystals precipitated by adding water to the residue was separated by filtration, washed with water and recrystallized from benzene to give 0.65 g of 5-chloro-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 17). Yield: 83 % m.p.: 220 °C Elementary Analysis: C₉H₈ClN₃O₂ C % H % N % Calculated 47.91 3.57 18.62 Found 47.91 3.47 18.45 NMR(DMSO-d₆): δ=3.29(3H,s), 3,50(3H,s), 7.47(1H,d,J=6Hz), 8.48(1H,d,J=6Hz) (3) 0.69 g of Compound 17 and 0.31 g of hydrazine hydrate were added to 20 ml of methanol and the solution was heated under reflux for 24 hr. The solvent was distilled off to give 0.63 g of 5-hydrazino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione (Compound 18). Yield: 93 % m.p.: 244 °C Elementary Analysis: C₉H₁₁N₅O₂ C % H % N % Calculated 48.86 5.01 31.66 Found 49.08 5.05 31.69 NMR(DMSO-d₆): δ=3.32(3H,s), 3.56(3H,s), 7.02(1H,d,J=7Hz), 8.32(1H,d,J=7Hz), 10.44(1H,br) 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 1 400 Compound 3 710 Compound 6 720 Compound 8 700 (2) Anti-allergic effect PCA (Passive Cutaneous Anaphylaxis) reaction in rats was taken as an index to an 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 1 20 85.3 Compound 3 20 77.3 Compound 4 20 89.3 Compound 6 20 92.0 Compound 7 20 72.7 Compound 8 20 73.4 Theophylline 20 78.7 As is clearly apparent from the above mentioned results, the pyrido[4,3-d]pyrimidine derivatives of the present invention have excellent anti-allergic properties which are superior to those of conventional pharmaceuticals, for example, theophylline. 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 into pharmaceutical compositions by combination with appropriate medicinal 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, antihistaminic 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 combination with an ointment base such as vaseline, paraffin, plastibase, simple ointment, hydrophilic ointment, hydrophilic vaseline 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 injection 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 containers 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/kg, preferably 5 to 600 mg/kg 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: A pyrido[4,3-d]pyrimidine derivative having the following formulae (Ia), (Ib) or (Ic): wherein each of R₁ and R₂, which may be the same or different, is an alkyl group having 1 to 5 carbon atoms; R₃ is hydrogen, halogen, hydroxy, amino, hydroxyamino, imino, hydrazino or an alkylamino group having 1 to 5 carbon atoms which may optionally have hydroxy, amino or an alkylamino group having 1 to 3 carbon atoms; and R₄ is amino, -NH ⊖ or an alkyl group having 1 to 5 carbon atoms which may optionally have hydroxy or an alkylamino group having 1 to 3 carbon atoms; or pharmaceutically acceptable salt thereof. A pyrido[4,3-d]pyrimidine derivative according to claim 1 wherein R₃ is amino or pharmaceutically acceptable salt thereof. A pyrido[4,3-d]pyrimidine derivative according to claim 2 which is 5-amino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione, 5-amino-1,3-diethylpyrido[4,3-d]pyrimidine-2,4-dione, 5-amino-1-isobutyl-3-methylpyrido[4,3-d]pyrimidine-2,4-dione, or pharmaceutically acceptable salt thereof. A pyrido[4,3-d]pyrimidine derivative according to claim 1 wherein R₃ is an alkylamino group having 1 to 5 carbon atoms or pharmaceutically acceptable salt thereof. A pyrido[4,3-d]pyrimidine derivative according to claim 4 which is 5-methylamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione, 5-methylamino-1,3-diethylpyrido[4,3-d]pyrimidine-2,4-dione, 5-isopropylamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione, or pharmaceutically acceptable salt thereof. A process for preparing a pyrido[4,3-d]pyrimidine derivative having the formulae (Ia), (Ib) or (Ic) or a pharmaceutically acceptable salt thereof as defined in any one of claims 1 to 5,which comprises reacting a compound having the formula (II): wherein each of R₁ and R₂, which may be the same or different, is an alkyl group having 1 to 5 carbon atoms and X is cyano or formyl; with a compound having the formula (III): wherein each of Y and Y', which may be the same or different, is hydrogen, hydroxy, amino or an alkyl group having 1 to 5 carbon atoms which may optionally have hydroxy, amino or an alkylamino group having 1 to 3 carbon atoms; and then, if desired, carrying out hydrolysis, halogenation or substitution reaction. A pharmaceutical composition which comprises a pharmaceutically acceptable carrier and an effective amount of a pyrido[4,3-d]pyrimidine derivative according to any one of claims 1 to 5 or pharmaceutically acceptable salt thereof. A pharmaceutical composition or salt according to claim 7 useful in the treatment of allergies. A pharmaceutical composition or salt according to claim 7 wherein said derivative is selected from: 1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-amino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-amino-1,3-diethylpyrido[4,3-d]pyrimidine-2,4-dione 5-methylamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-methylamino-1,3-diethylpyrido[4,3-d]pyrimidine-2,4-dione 5-isopropylamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione Use of a pyrido[4,3-d]pyrimidine derivative according to any one of claims 1 to 5 or pharmaceutically acceptable salt thereof for the manufacture of a drug for the treatment of allergies. Use according to claim 10 wherein said derivative is selected from: 1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-amino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-amino-1,3-diethylpyrido[4,3-d]pyrimidine-2,4-dione 5-methylamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione 5-methylamino-1,3-diethylpyrido[4,3-d]pyrimidine-2,4-dione 5-isopropylamino-1,3-dimethylpyrido[4,3-d]pyrimidine-2,4-dione

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