Condensed purine derivatives

Abstract: There are disclosed condensed purine derivatives represented by formula: alkyl or benzyl; each of X¹ and X² independently represents hydrogen, lower alkyl, aralkyl or phenyl; and n is an integer of 0 or 1; R¹ represents hydrogen, lower alkyl, alicyclic alkyl, noradamantan-3-yl, dicyclopropylmethyl or styryl; and R² represents hydrogen, lower alkyl or alicyclic alkyl; or a pharmaceutically acceptable salt thereof. The derivatives and pharmaceutically acceptable salts are useful as diuretics, renal protecting agents, antiallergic agents and hypotensives.

Description: The present invention relates to novel purine derivatives which possess diuretic,.renal protecting, bronchodilatory, antiallergic and hypotensive effects. As condensed purine derivatives which are structurally analogous to the presently claimed compounds, a compound represented by formula (A) and having a slight bronchodilatory effect is disclosed in J. Med. Chem., 23 , 1188 (1980): Compounds represented by formula (B) are disclosed in Liebigs. Ann. Chem., 11 , 1872 (1979): where Q is NH or O. In J. Med. Chem. 1980, 23, 1188-1198 and FR-A 2380282 imidazo[1,2a]purin-9(4H)-ones are disclosed. EP-A 0390111 discloses purine derivatives which do not have a keto function in the 5 position An object of the present invention is to provide novel condensed purine derivatives represented by the formula (I): in which R 3 represents hydrogen or C 1 -C 6 alkyl or benzyl, each of X 1 and X 2 independently represents hydrogen, C 1 -C 6 alkyl, C 7 -C 15 aralkyl or phenyl; R 1 represents hydrogen, C 1 -C 6 alkyl, C 3 -C 6 cycloalkyl, noradamantan-3-yl, dicyclopropylmethyl or styryl; and R 2 represents hydrogen or C 1 -C 6 alkyl or C 3 -C 6 cycloalkyl; or a pharmaceutically acceptable salt thereof. In the definitions of the groups in formula (I), the alkyl having 1 to 6 carbon atoms refers to a straight or branched alkyl and includes, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl and hexyl. The cycloalkyl of 3 to 6 carbon atoms includes, for example, cyclopropyl, cyclopentyl and cyclohexyl. The aralkyl of 7 to 15 carbon atoms includes, for example, benzyl and phenethyl. The pharmaceutically acceptable salts of Compound (I) include acid addition salts, metal salts, ammonium salts, organic amine addition salts and amino acid addition salts. The pharmaceutically acceptable acid addition salts of Compound (I), induce inorganic acid salts such as hydrochloride, sulfate, phosphate, and organic acid salts such as acetate, maleate, fumarate, tartrate and citrate. The pharmaceutically acceptable metal salts include alkali metal salts such as sodium salts and potassium salts; alkaline earth metal salts such as magnesium and calcium salts, and further aluminum and zinc salts. The pharmaceutically acceptable organic amine addition salts include addition salts of e.g. morpholine and piperidine. The pharmaceutically acceptable amino acid addition salts include e.g. salts with lysine, glycine and phenylalanine. The methods for preparing Compound (I) are described below. When the defined groups are changed under the conditions of the following processes or are inadequate to proceeding of the following processes, processes can be readily carried out by a usual method in the organic synthetic chemistry, for example, by protection of functional groups, elimination of protecting groups. Process 1 Compounds of formula (I), are synthesized according to the following reaction steps. wherein R 1 ,R 2 , R 3 , X 1 and X 2 have the same significance as described above. Compound (IV) is obtained by reacting Compound (II) with Compound (III) in the absence or presence of a solvent. Any solvent is used so long as it is inert to the reaction. The solvent includes, for example, dimethylamines such as dimethylformamide and dimethylacetamide; kentones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as dichloroethane and 1,1,2,2-tetrachloroethane; and dimethylsulfoxide. The solvent is used alone or in combination. The reaction is carried out at 50 to 180°C and completed in 5 minutes to 24 hours. The starting Compound (II) is synthesized by a notorious method [J. Chem. Soc. Perkin I, 739 (1973)] or by a modified method of Perkin. The starting Compound (III) is commercially available. Compound (I) is obtained by reacting Compound (IV) with a halogenating agent or an inorganic acid in the absence or presence of a solvent. The halogenating agent includes, for example, thionyl chloride and phosphorus oxychloride. The inorganic acid includes, for example, hydrochloric acid, hydrobromic acid, hydroiodic acid and phosphoric acid. The solvent includes, for example, halogenated hydrocarbons such as methylene chloride, chloroform and dichloroethane; dimethylformamide and dimethylsulfoxide. The solvent is used alone or in combination. The reaction is carried out at -10 to 150°C and completed in 5 minutes to 24 hours. Process 2 Compounds (I) where R 2 represents groups other than hydrogen and Compounds I obtained in Process 1 where R 2 represents hydrogen. Compounds I wherein R 2 is other than hydrogen are obtained by reacting Compounds I wherein R 2 is H with Compound (XI) represented by the following formula in the presence or absence of a base. R 2a - Z wherein Z represents a leaving group and R 2a has the same significance as that of R 2 except for hydrogen. Examples of the leaving group denoted by Z include halogen such as chlorine, bromine and iodine; alkylsulfonyloxy such as methanesulfonyloxy; and arylsulfonyloxy such as phenylsulfonyloxy and p-toluenesulfonyloxy. The base includes, for example, alkali metal carbonates such as potassium carbonate and sodium carbonate; alkali metal hydrides such as sodium hydride; and alkali metal alkoxides such as sodium methoxide and sodium ethoxide. The solvent is used alone or in combination, and includes, for example, ethers such as tetrahydrofuran and dioxane; amides such as dimethylformamide ; alcohols such as methanol and ethanol; and dimethylsulfoxide. The reaction is carried out at 0 to 180°C and completed in 30 minutes to 24 hours. The intermediates and objective compounds in the respective methods described above can be isolated and purified by purification methods conventionally used in organic synthesis chemistry, for example, filtration, extraction, washing, drying, concentration, recrystallization and various column chromatographies. Furthermore, the intermediates may also be provided in the subsequent reaction, without being further purified. In the case that it is desired to obtain salts of Compound (I), when Compound (I) is obtained in the form of its salt, Compound (I) may be purified as it is. Further in the case that Compound (I) is obtained in the free form, its salts may be formed in a conventional manner, for example, Compound (I) is suspended or dissolved in an appropriate solvent, and an acid or base is added to the solution or suspension. Furthermore, Compound (I) and pharmaceutically acceptable salts thereof may also be present in the form of addition products to water or to various solvents; in this case, the addition products are also included in the present invention. Furthermore, some of Compounds (I) may have optical isomers. In the present invention, all possible stereoisomers and their mixtures are all included. Specific examples of Compound (I) are shown in Table 1. Compound (I) or its pharmaceutically acceptable salts have diuretic, renal protecting, bronchodilatory and hypotensive activities. Accordingly, Compound (I) or its pharmaceutically acceptable salts are useful as diuretics, renal protecting agents, bronchodilatory agents, antiallergic agents and hypotensives. Next, pharmaceutical- activities of Compound (I) are explained below. (1) Acute toxicity The compounds were orally administrated to male dd-mice weighing 20 ±1 g. Minimum lethal dose (MLD) was determined by observing the mortality for seven days after the administration. The results are shown in Table 2. Compound MLD (mg/kg) Compound MLD (mg/kg) 1 >300 11Sa >300 3 >300 12Sa >300 4 >300 14Sa >300 15Sa >300 16Sa >300 8Sa >300 9Sa >300 (2) Diuretic activity Wistar male rats weighing 150 to 300 g were used after they were fasted for 18 hours. A test compound or saline (control) was orally administered to rats and urine was collected for 6 hours. The test was performed using 3 groups per the test compound, and each group consists of 3 animals. The urine was metered by a measuring cylinder and electrolytes (Na + and K + ) in the urine were assayed with a flame photometer (model 775A manufactured by Hitachi Ltd.). The results are shown in Table 3. Parameters in Table 3 are all expressed by relative value for control. Compound Dose (mg/kg) Urine volume (%) Excretion of Na + (%) Excretion of K + (%) Na + /K + Control - 0 0 0 1.00 4 25 165 197 77 1.67 5 1.6 121 102 30 1.55 6 25 128 114 56 1.37 7 6.25 42 46 1 1.45 9Sa 1.6 159 102 33 1.52 10Sa 6.25 140 92 18 1.63 11Sa 6.25 113 73 43 1.23 25 145 162 31 2.00 12Sa 6.25 137 153 9 2.32 25 95 90 26 1.51 13Sa 1.6 80 99 31 1.52 14Sa 6.25 138 158 18 2.91 15Sa 25 92 65 37 1.20 16Sa 25 111 87 31 1.43 Furosemide 25 75 64 57 1.07 (3) Effect on renal protecting activity (glycerol-induced renal deficient model): Renal insufficiency is the condition that homeostasis of body fluid failed to maintain by disorder of renal function. It is well known that subcutaneous or intramuscular administration of glycerol to rat induces acute renal insufficiency characterized by renal tubular disturbance [Can J. Physiol. Pharmacol., 65 , 42 (1987)]. Wistar male rats (fasted both food and water for 18 hours) were used. A test compound or saline (control) was intraperitoneally administered (dose: 10 mg/kg) to rats. After 30 minutes rats were anesthesized with ether and the back skin was picked up and 0.8 ml/100 g of 50% glycerol was subcutaneously administered. 24 hours after the glycerol injection, the rats were anesthesized with ether and 5 ml of the blood was collected from the descending aorta. To obtain the serum, after allowing it to stand for 30 minutes or longer, the blood sample was centrifuged at 3000 rpm for 10 minutes. Creatinine in the serum sample was determined using autoanalyzer (AU510, Olympus) or clinical analysis kit of creatinine (Creatinine Test Wako; by Wako Pure Chemical Ind., Japan). Urea nitrogen in the serum was determined using autoanalyzer (AU510; made by Olympus Optical Co., Ltd, Japan) or clinical analysis kit of urea nitrogen (Urea nitrogen test wako; by Wako Pure Chemical Ind., Japan). The results are shown in Table 4. Further, the left kidneys of test compound-treated groups and control groups were taken out from the animals and the kidneys were prepared for pathological sample. As the result of pathologic autopsy for kidneys, it was indicated that the renal insufficiency was improved by the test compounds as shown in Table 4. Creatinine in serum (mg/dl) Urea nitrogen in serum (mg/dl) Compound No. Glycerol treated Glycerol treated Control Test compound administrated (Significance for control ) Control Test compound administrated (Significance for control ) 1 2.64±0.27 1.94±0.16 P<0.005 2 2.49±0.43 1.63±0.19 P<0.1 5 5.01±0.19 1.81±0.12 P<0.001 6 3.63±0.29 1.70±0.17 P<0.001 137.9±8.5 64.3± 7.1 P<0.001 7 4.64±0.24 3.17±0.32 P<0.01 147.0±5.8 121.2± 9.0 P<0.05 11Sa 4.81±0.09 2.62±0.40 P<0.01 168.5±3.5 94.8±14.3 P<0.01 12Sa 4.81±0.09 2.34±0.12 P<0.001 168.5±3.5 101.8±11.8 P<0.01 13Sa 4.81±0.09 2.38±0.24 P<0.001 168.5±3.5 80.9± 9.5 P<0.001 14Sa 4.31±0.12 2.35±0.11 P<0.001 147.1±4.4 88.0± 4.9 P<0.001 15Sa 4.31±0.12 2.85±0.33 P<0.01 147.1±4.4 101.2± 9.9 P<0.01 Aminophylline 2.03±0.18 1.72±0.07 N.S. 46.2±6.5 30.6± 2.0 P<0.05 Furosemide 3.22±0.35 4.17±0.41 N.S. 110.7±9.4 150.3±13.7 P<0.05 Normal control Glycerol untreated 0.50 ±0.02 Glycerol untreated 15.2 ±0.9 N.S. No significant difference Sa is hydrochloride of the compound. (4) Effects on passive Schultz-Dale reaction (bronchodilatory effects) Guinea pigs were passively sensitized as follows. Hartley male guinea pigs weighing 350 to 500 g were injected intraperitoneally with rabbit anti-egg albumin (EWA) serum prepared by the method of Koda et al. [Folia pharmacol., Japon 66 , 237, (1970)]. After 24 hours, the guinea pigs were stunned and exsanguinated, and then trachea was excised. The zig-zag strips of the trachea were prepared by the method of Emmerson and Mackay [J. Pharm. Pharmacol., 31 , 798, (1979)]. The strips were suspended in Krebs-Henseleit solution at 37°C under aeration or a mixed gas of 95% oxygen and 5% carbon dioxide, and incubated for one hour. Antigen (EWA) was then introduced in the solution (final concentration; 1 µg/ml), and the contraction was measured by isotonic transducer (TD-112s, made by Nihon Kohden K.K., Japan) and recorded on a recorder (Type 3066, made by Yokogawa-Hokushin Denki, K.K. Japan). After the contraction curves reached plateau the compounds were successively added in order to get cumulative concentration-relaxation curves. Concentration of 50% relaxation rate (IC 50 ) was calculated from the regression line, which was obtained from cumulative concentration-relaxation curves. The results are shown in Table 5. (5) Inhibition effect on platelet activating factor (PAF)-induced mortality The experiment was performed by a minor modification of method of Carlson et al. [Agents and Actions, 21 , 379 (1987)]. Groups each consisting of 10 male dd mice (weighing 28 to 32 g) were used, and 100 mg/kg of test compound or a saline (control) was orally administrated. One hour after the administration of test compound, 40 µg/kg of PAF (manufactured by Avanti Polar Lipids Co., Ltd.) was intravenously administered. Two hours after PAF injection, the mortality rate of the animals was observed. The compound whose mortality rate was significantly (p <0.05: Fischer's accurate probability tests) lower than control is regarded as having inhibitory effect on PAF-induced mortality, and the results in Table 5 were represented by minimum effective dose (MED). Compound No. Passive S -D reaction IC 50 (µM) PAF-induced mortality inhibition MED (mg/kg) 1 0.0030 >100 2 21 100 3 0.036 >100 4 32 NT 5 >40 50 6 8.1 >100 7 72 NT 11Sa 11 100 12Sa >40 100 Theophylline 23 100 Sa is hydrochloride of the compound. (6) Effects on experimental asthma Guinea pigs were passively sensitized as follows. Hartley male guinea pigs weighing 350 to 500 g were intraperitoneally injected with 1 ml of rabbit anti-egg alubmin (EWA) serum prepared by the method of Koda et al. [Folia pharmacol., Japon, 66 , 237 (1970)]. The animals were treated with intraperitoneal injection of diphenhydramine (20 mg/kg) and propranolol (5 mg/kg), 30 minutes before administration of test compounds. 17 hours after the sensitization, the test compounds (50 mg/kg) or saline (control) were orally administrated to sensitized animals. After one hour from the administration of the test compounds, the guinea pigs were placed in plastic observation box and were exposed to an aerosal antigen of 1.5% EWA. The time until the onset of respiratory distress-like symptom [collapse time (second)] was measured as a result of experimental asthma. The results are shown in Table 6. Compound Experimental asthma Collapse time (sec) 2 552 ± 20 4 542 ± 36 10Sa 374 ± 76 Theophylline 414 ± 47 Control 254 ± 18 Sa is hydrochloride of the compound. Compounds (I) or their pharmaceutically acceptable salts are used directly or in various dosage forms. In the present invention, pharmaceutical compositions are prepared by homogeneously mixing an effective amount or Compound (I) or its pharmaceutically acceptable salt with pharmaceutically acceptable carrier. It is desirable that the pharmaceutical compositions are an appropriative dosable unit for oral administration or injection administration. In the preparation of orally administrated forms, any of useful pharmaceutically acceptable carriers are used. In the case of orally administrated liquid preparates such as suspensions and syrups, for example, water, saccharides such as sucrose, sorbitol and fructose; glycols such as polyethyleneglycol end propyleneglycol; oils such as sesame oil, olive oil and soybean oil; antiseptics such as p-hydroxybenzoic acid esters; and flavors such as strawberry flavor and peppermint are used. In the case of powders, pills, capsules and tablets; vehicles such as lactose, glucose, sucrose and mannitol; disintegrators such as starch, and sodium alginate; lubricants such as magnesium stearate and talc; binders such as polyvinyl alcohol, hydroxypropyl cellulose and gelatin; surfactants such as fatty acid esters and plasticizers such as glycerine, are used. Tablets and capsules are most useful dosage form for oral administration because of easy administration. In the preparation of tablets and capsules, solid medicament carriers are used. Injection solutions are prepared with such a carrier as distilled water, a salt solution, a glucose solution, or a mixture of a salt solution and a glucose solution. Effective dose and the number of administration of Compound (I) or its pharmaceutically acceptable salt depend on modes of administration and ages, body weight, and symptoms of patients. It is preferable to usually administer 1 to 50 mg/kg or Compound (I) or its pharmaceutically acceptable salt daily in 3 to 4 portions. Furthermore, Compound (I) is administrated by inhalation in the form of aerosol, finely pulverized powders, or spray solution. In the case or aerosol administration, the present compound is dissolved in a pharmaceutically acceptable solvent, for example, ethyl alcohol or a combination of miscible solvents and then mixed with a pharmaceutically acceptable propellant. Hereafter the present invention is described by referring to examples of the present invention and reference examples. Example 1 1-Methyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 1): After 50 ml of ethanolamine was added to 5.00 g or Compound a obtained in Reference Example 1, the mixture was heated at 160°C for an hour. After cooling, the reaction mixture was concentrated to the half in volume under reduced pressure. Ethanol was added to the concentrate and the precipitate was collected by filtration. Recrystallization from ethanol gave 3.52 g (67%) of 3,7-dihydro-6-(2-hydroxyethylamino)-7-methyl-3-n-propyl-2H-purin-2-one (Compound ml) as white plates. Elemental analysis: as C 11 H 17 N 5 O 2 Found (%): C 52.41 H 6.80 N 27.54 Calcd. (%): C 52.58 H 6.82 N 27.87 1 H-NMR (DMSO-d 6 , 90 MHz) δ (ppm): 6.82(brs, 1H), 4.87 (brs, 1H), 3.92(s, 3H), 3.91(t, 2H), 3.63-3.40 (m, 4H), 1.80-1.45(m, 2H), 0.88(t, 3H) After 15 ml of phosphorus oxychloride was added to 3.50 g (13.9 mmol) of Compound ml under ice cooling, the mixture was refluxed for 2 hours. Then the mixture was concentrated under reduced pressure. After neutralizing with 2 N aqueous sodium hydroxide solution, the mixture was extracted 3 times with chloroform. After washing with saturated sodium chloride aqueous solution, the extract was dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure. The residue was isolated and purified by silica gel column chromatography (eluting solvent: 2% methanol/chloroform) and then recrystallized from toluene to afford 1.27 g (39%) of Compound 1 as white needles. Melting point: 109.9-111.6°C (toluene) Elemental analysis: as C 11 H 15 N 5 O Found (%): C 56.49 H 6.57 N 30.23 Calcd. (%): C 56.64 H 6.48 N 30.02 IR (KBr) νmax (cm -1 ): 1685, 1657 1 H-NMR (CDCl 3 ) δ (ppm): 7.43(s, 1H), 4.15-4.05(m, 2H), 3.95(s, 3H), 4.05-3.90(m, 4H), 1.90-1.70(m, 2H), 0.97(t, 3H) Example 2 4-n-Propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 2): The procedure was performed in a manner similar to Example 1 except for using 4 g (17.9 mmol) of Compound b obtained in Reference Example 2. Thus, 3.24 g (77%) of 3,7-dihydro-6-(2-hydroxyethylamino)-3-n-propyl-2H-purin-2-one (Compound m2) was obtained as a white powder. 1 H-NMR (DMSO-d 6 , 90 MHz) δ (ppm): 7.82(s, 1H), 7.50 (brs, 1H), 3.88(t, 2H), 3.80-3.00(m, 5H), 1.90-1.40(m, 2H), 0.86(t, 3H) Using 3.50 g (14.8 mmol) of the Compound m2, cyclization with phosphorus oxychloride was performed in a manner similar to Example 1 to afford 2.05 g (63%) of Compound 2 as a white powder. Melting point: 282.8-284.9°C (water) Elemental analysis: as C 10 H 13 N 5 O Found(%): C 54.54 H 6.05 N 32.15 Calcd. (%): C 54.78 H 5.98 N 31.94 IR (KBr) νmax (cm -1 ): 1718, 1660, 1550 1 H-NMR (DMSO-d 6 -DCl) δ (ppm): 7.70 (s, 1H), 4.12-3.85 (m, 6H), 1.80-1.60 (m, 2H), 0.58 (t, 3H) 13 C-NMR (DMSO-d 6 ) δ (ppm): 151.0, 149.1, 146.7, 143.9, 100.3, 45.3, 45.2, 20.6, 10.7 Example 3 8-Ethyl-1-methyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 3) Using 4.00 g (16.8 mmol) of Compound a obtained in Reference Example 1 and 10 ml of 2-amino-1-butanol, the procedure was performed in a manner similar to Example 1 to afford 3,34 g (71 %) of 3,7-dihydro-6-(1-ethyl-2-hydroxyethylamino)-7-methyl-3-n-propyl-2H-purin-2-one (Compound m3) as a white powder. 1 H-NMR (CDCl 3 ) δ (ppm): 7.42 (s, 1H), 6.30-5.70 (br, 1H), 4.40-3.50 (m, 6H), 4.00 (s, 3H), 1.95-1.40 (m, 4H), 1.05-0.70 (m, 6H) Using 3.20 g (11.5 mmol) of the compound m3, cyclization with phosphorus oxychloride was performed in a manner similar to Example 1 to afford 2.06 g (69 %) of Compound 3 as white needles. Melting point: 123.8-125.5°C (cyclohexane) Elemental analysis: as C 13 H 19 N 5 O·0.3 H 2 O Found(%): C 58.30 H 7.68 N 26.50 Calcd. (%): C 58.54 H 7.41 N 26.26 IR (KBr) νmax (cm -1 ): 1698, 1668, 1655 1 H-NMR (CDCl 3 ) δ (ppm): 7.43 (s, 1H), 4.23-4.18 (m, 1H), 4.05-3.91 (m, 3H), 3.97 (s, 3H), 3.64-3.53 (m, 1H), 1.90-1.50 (m, 4H), 1.08-0.93 (m, 6H) Example 4 1-Methyl-7-phenyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 4) After 2.00 g (8.20 mmol) of Compound a obtained in Reference Example 1 was dissolved in 5 ml of dimethylsulfoxide, 5.76 g (42 mmol) of 2-amino-1-phenylethanol was added to the solution. Then the mixture was heated at 150°C for an hour with stirring. After cooling, 100 ml of water was added and the mixture was extracted 4 times with chloroform. After washing with saturated aqueous sodium chloride solution, the extract was dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure. The residue was isolated and purified by silica gel column chromatography (eluting solvent: 10 % methanol/chloroform) to afford 1.67 g (62 %) of 3,7-dihydro-6-(2-hydroxy-2-phenyl) ethylamino-7-methyl-3-n-propyl-2H-purin-2-one (Compound m4) as a white powder. 1 H-NMR (DMSO-d 6 -D 2 O, 90 MHz) δ (ppm): 8.30 (s, 1H), 7.60-7.20 (m, 5H), 4.94 (dd, 1H, J=5, 8Hz), 4.07 (s, 3H), 4.20-3.70 (m, 7H), 1.90-1.45 (m, 2H), 0.91 (t, 3H) After 20 ml of thionyl chloride was added to 1.51 g (4.61 mmol) of Compound m4, the mixture was stirred for 20 minutes. After concentration under reduced pressure, the reaction mixture was neutralized with 2 N aqueous sodium hydroxide solution under ice cooling followed by extraction 3 times with chloroform. After washing with aqueous saturated sodium chloride solution, the extract was dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (eluting solvent: 5 % methanol/chloroform) to afford 1.44 g (95 %) of Compound 4 as white needles. Melting point: 152.2-153.6°C (toluene-cyclohexane) Elemental analysis: as C 17 H 19 N 5 O Found(%): C 66.29 H 6.19 N 22.72 Calcd. (%): C 66.00 H 6.19 N 22.64 IR (KBr) νmax (cm - 1 ): 1693, 1651 1 H-NMR (CDCl 3 ) δ (ppm): 7.45 (s, 1H), 7.40-7.20 (m, 5H), 5.29 (dd, 1H, J=5.3, 10.7Hz), 4.49 (dd, 1H, J=10.7, 14.8Hz), 3.99 (dd, 1H, J=5.3, 14.8Hz), 3.87 (t, 2H), 1.80-1.60 (m, 2H), 0.90 (t, 3H) Example 5 2-Cyclopentyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo-[2,1-i]purin-5-one (Compound 5). The procedure was performed in a manner similar to Example 1 except for using 5.00 g (17.1 mmol) of Compound e obtained in Reference Example 5 to afford 4.81 g (89%) of 8-cyclopentyl-3,7-dihydro-6-(2-hydroxyethylamino)-3-n-propyl-2H-purin-2-one (Compound m5) as a white powder. 1 H-NMR (DMSO-d 6 , 90 MHz) δ (ppm): 7.08(brs, 1H), 3.89 (t, 2H), 3.56(s, 3H), 4.00-3.00(m, 6H), 2.20-1.45 (m, 10H) 0.88(t, 3H) In a manner similar to Example 4, 3.08 g (10.1 mmol) of the Compound m5 was subjected to cyclization with thionyl chloride to afford 3.00 g (quantitative) of Compound 5 as white crystals. Melting point: 214.9-216.1°C (dioxane) Elemental analysis: as C 15 H 21 N 5 O·1.3H 2 O Found (%): C 57.90 H 7.29 N 22.63 Calcd. (%): C 57.97 H 7.65 N 22.53 IR (KBr) νmax (cm -1 ) : 1712, 1670, 1588 1 H-NMR (DMSO-d 6 ) δ (ppm): 4.28-4.16(m, 2H), 4.12-3.90 (m, 4H), 3.40-3.25(m, 1H), 2.20-2.00(m, 2H), 1.90-1.60(m, 8H), 0.90(t, 3H) Example 6 2-Cyclopentyl-1-methyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 6). The procedure was performed in a manner similar to Example 1 except for using 1.30 g (4.25 mmol) of Compound f obtained in Reference Example 6. Thus, 1.26 g (93%) of 8-cyclopentyl-3,7-dihydro-6-(2-hydroxyethylamino)-7-methyl-3-n-propyl-2H-purin-2-one (Compound m6) was obtained as a white powder. 1 H-NMR (DMSO-d 6 , 90 MHz) δ (ppm): 3.93(s, 3H), 3.92(t, 2H), 3.70-3.10(m, 5H), 2.10-1.45(m, 10H), 0.88(t, 3H) In a manner similar to Example 4, 1.10 g (3.44 mmol) of Compound m7 was subjected to cyclization with thionyl chloride to afford 583 mg (56%) of Compound 7 as a white needle. Melting point: 245.5-247.1°C (propanol-water) IR (KBr) νmax (cm -1 ): 1712, 1686, 1662 1 H-NMR (DMSO-d 6 ) δ (ppm): 3.95(s, 3H), 3.87(t, 2H), 3.85(s, 4H), 3.40-3.20(m, 1H), 2.10-1.95(m, 2H), 1.90-1.60(m, 3H), 0.86(t, 3H) MS (m/e) relative intensity: 301(M + ), 272, 260 Example 7 2-Cyclopentyl-8-ethyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 7). The procedure was performed in a manner similar to Example 1 except for using 3.00 g (10.3 mmol) of Compound e obtained in Reference Example 5. Thus, 2.63 g (77%) of 8-cyclopentyl-3,7-dihydro-6-(1-ethyl-2-hydroxyethyl)amino-3-n-propyl-2H-purin-2-one (Compound m7) was obtained as a white powder. 1 H-NMR (CDCl 3 , 90 MHz) δ (ppm): 7.60(brs, 1H), 4.12 (t, 2H); 4.30-3.00(m, 7H), 2.35-1.10(m, 12H), 0.97(t, 3H), 0.68(t, 3H) In a manner similar to Example 4, 2.20 g (6.60 mmol) of the Compound m7 was subjected to cyclization. The crude product was dissolved in 10 ml of methanol. 1 ml of methanol solution saturated with hydrogen chloride was added under ice cooling. The mixture was concentrated under reduced pressure. The resulting light yellow powders were recrystallized from ethanol to afford 542 mg (26%) of the hydrochloride of Compound 7 as a light yellow needle. Melting point: 208.8-209.6°C Elemental analysis: as C 17 H 25 N 5 O·HCl Found (%): C 58.22 H 7.63 N 19.74 Calcd. (%): C 58.03 H 7.45 N 19.90 IR (KBr) νmax (cm -1 ): 1717, 1687, 1588 1 H-NMR (DMSO-d 6 ) δ (ppm): 14.0-13.4(br, 1H), 11.2-10.7 (br, 1H), 4.40-4.25(m, 2H), 3.98(t, 2H), 3.90-3.80 (m, 1H), 3.45-3.30(m, 1H), 2.20-2.05(m, 2H), 1.90-1.60(m, 8H), 0.97(t, 3H), 0.90(t, 3H) The same procedures as in Example 4 were performed in Examples 8 to 16 except that amino alcohols shown in Table 7 and 3.00 g (10.3 mmol) of Compound e obtained in Reference Example 5 were used. The physicochemical data of Compounds 8 to 16 were given in Table 8. Example 8 2-Cyclopentyl-7-phenyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 8). Example 9 8-Benzyl-2-cyclopentyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 9). Example 10 2-Cyclopentyl-8-isopropyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 10). Example 11 2-Cyclopentyl-8,8-dimethyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 11) Example 12 2-Cyclopentyl-8-phenyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 12) Example 13 2-Cyclopentyl-8-methyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 13) Example 14 2-Cyclopentyl-4,8-di-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 14) Example 15 2-Cyclopentyl-7-ethyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 15) Example 16 2-Cyclopentyl-7-methyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 16) Example No. Aminoalcohol Yield (%) 8 2-Amino-1-phenylethanol 64 9 2-Benzyl-2-aminoethanol 71 10 2-Amino-3-methylbutanol 61 11 2-Amino-2-methyl-1-propanol 42 12 2-Phenylglycinol 49 13 2-Amino-1-propanol 85 14 2-Amino-1-pentanol 65 15 1-Amino-2-butanol 86 16 1-Amino-2-propanol 73 Example 17 8-Ethyl-2-(noradamantan-3-yl)-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 17). The procedure was performed in a manner similar to Example 4 except for using 3.00 g (8.72 mmol) of Compound g obtained in Reference Example 7 and 4.14 ml (43.6 mmol) of 2-amino-1-butanol. Thus 3.00 g (yield, 89%) of 3,7-dihydro-6-(1-ethyl-2-hydroxyethylamino)-8-(noradamantan-3-yl)-3-n-propyl-2H-purin-2-one (Compound m17) was obtained as a light yellow powder. 1 H-NMR (CDCl 3 , 90 MHz) δ (ppm): 4.00-3.70(m, 5H), 2.82(t, 1H), 2.30-1.35(m, 16H), 1.05-0.85(m, 6H) Using 2.78 g (7.22 mmol) of Compound m17, cyclization with thionyl chloride was performed in a manner similar to Example 7 to afford 1.52 g (yield, 52%) of hydrochloride of Compound 17 as light yellow needles. Melting point: 196.3-201.3°C (ethylacetate) Elemental analysis: as C 21 H 29 N 5 O·HCl·0.25H 2 O Found (%): C 61.66 H 7.51 N 17.00 Calcd. (%): C 61.75 H 7.53 N 17.15 IR (KBr) νmax (cm -1 ): 1714, 1631, 1594 1 H-NMR (CDCl 3 , 90 MHz) δ (ppm): 4.50-3.90(m, 5H), 2.70(t, 1H), 2.55-1.60(m, 16H), 1.10(t, 3H), 0.96(t, 3H) Example 18 2-(Dicyclopropylmethyl)-8-ethyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 18), The procedure was performed in a manner similar to Example 4 except for using 2.60 g (8.17 mmol) of Compound h obtained in Reference Example 8 and 5 ml of 2-amino-1-butanol. Thus, 2.17 g (yield, 74%) of 8-(dicyclopropylmethyl)-3,7-dihydro-6-(1-ethyl-2-hydroxyethylamino)-3-n-propyl-2H-purin-2-one (Compound m18) was obtained as a light yellow powder. 1 H-NMR (DMSO-d 6 , 90 MHz) δ (ppm): 12.2(brs, 1H), 7.20 (brs, 1H), 4.30-3.30(m, 6H), 2.00-0.10(m, 21H) Using 2.03 g (5.65 mmol) of Compound m21, cyclization with thionyl chloride was performed in a manner similar to Example 7 to afford 1.66 g (yield, 86%) of hydrochloride of Compound 21 as a light yellow powder. Melting point: 153.1-157.2°C (cyclohexane-toluene) Elemental analysis: as C 19 H 2 N 5 O·HCl·1/4H 2 O Found (%): C 59.62 H 7.46 N 18.40 Calcd. (%): C 59.67 H 7.51 N 18.31 IR (KBr) νmax (cm -1 ): 1720, 1678, 1591 1 H-NMR (CDCl 3 , 90 MHz) δ (ppm): 4.50-3.90(m, 3H), 4.05(t, 2H), 2.00-1.60(m, 5H), 1.25-0.25(m, 16H), MS (m/e, relative intensity): 341(M + , 12), 312(100) Example 19 8-Ethyl-1-methyl-4-n-propyl-2-styryl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 19). The procedure was performed in a manner similar to Example 4 except for using 1.72 g (5.06 mmol) of Compound j obtained in Reference Example 10. Thus, 1.49 g (yield, 77%) of 3,7-dihydro-6-(1-ethyl-2-hydroxyethylamino)-7-methyl-3-n-propyl-8-styryl-2H-purin-2-one (Compound m19) was obtained as a light yellow powder. 1 H-NMR (CDCl 3 , 90 MHz) δ (ppm): 7.70(d, J=15.0Hz, 1H), 7.65-7.15(m, 5H), 6.86(d, J=15.0Hz, 1H), 4.50-3.55(m, 5H), 3.97(s, 3H), 2.00-1.45(m, 4H), 1.15-0.80(m, 6H) Using 1.30 g (3.41 mmol) of Compound m22, cyclization with thionyl chloride was performed in a manner similar to Example 7 to afford 530 mg (yield, 39%) of hydrochloride of Compound 19 as a white powder. Melting point: 198.7-203.4°C (isopropanol) IR (KBr) νmax (cm -1 ): 1706, 1670 1 H-NMR (DMSO-d 6 , 90 MHz) δ (ppm): 8.05-7.75(m, 3H), 7.60-7.30 (m, 4H), 4.45-3.80(m, 5H), 4.20(s, 3H), 2.00-1.60(m, 4H), 1.10-0.85(m, 6H) MS (m/e, relative intensity): 363(M + , 17), 334(100) Example 20 7-Phenyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one (Compound 20). The procedure was performed in a manner similar to Example 4 except for using 3.00 g (13.4 mmol) of Compound b obtained in Reference Example 2 and 9.10 g (67.0 mmol) of 2-amino-1-phenylethanol. Thus, 3.66 g (yield, 87%) of 3,7-dihydro-6-(2-hydroxy-2-phenyl)ethylamino-3-n-propyl-2H-purin-2-one (Compound m20) was obtained as a white powder. 1 H-NMR (DMSO-d 6 , 90 MHz) δ (ppm): 7.87(s, 1H), 7.65-7.20(m, 5H), 5.80(brs 1H), 4.80(dd, J=5.0, 9.0Hz, 1H), 4.00-3.50(m, 4H), 1.80-1.45(m, 2H), 0.89(t, 3H) Using 3.47 g (11.1 mmol) of Compound m23, cyclization with thionyl chloride was performed in a manner similar to Example 7 to afford 1.95 g (yield, 60%) of Compound 20 as white needles. Melting point: 258.2-263.5°C (ethanol) Elemental analysis: as C 16 H 17 N 5 O·HCl·0.1H 2 O Found (%): C 57.47 H 5.38 N 21.19 Calcd. (%): C 57.61 H 5.50 N 20.99 IR (KBr) νmax (cm -1 ): 1709, 1670, 1588 1 H-NMR (DMSO-d 6 , 90 MHz) δ (ppm): 8.11 (s, 1H), 7.43 (s, 5H), 5.80(dd, J=5, 10Hz, 1H), 4.53(dd, J= 10, 10Hz, 1H), 4.15-3.80(m, 3H), 1.85-1.50(m, 2H), 0.88(t, 3H) MS (m/e, relative intensity): 295(M + , 100), 266 (41), 253(20) Reference Example 1 3,7-Dihydro-7-methyl-6-methylthio-3-n-propyl-2H-purin-2-one (Compound a ) Under an argon atmosphere, 10.7 g (268 mmol) of 60% sodium hydride was washed 3 times with n-hexane. The solvent was evaporated under reduced pressure to dry. To the residue was added 300 ml of dimethylformamide. A suspension of 3-n-propyl-6-thioxanthine (Japanese Published Unexamined Patent Application No. 183286/86) (28.2 g, 134 mmol) in 200 ml of dimethylformamide was dropwise added to the mixture under ice cooling with stirring. 15 minutes after, 25.1 ml (403 mmol) of methyl iodide was dropwise added to the reaction mixture. After stirring was continued for 30 minutes, 50 ml of ethanol was added and the mixture was concentrated. 250 ml of water was added to the residue and the precipitate was collected by filtration to give 25.9 g (yield, 81%) of Compound a . Melting point: 224.7-226.4°C (acetonitrile) Elemental analysis: as C 10 H 14 N 4 OS Found (%): C 50.30 H 5.95 N 23.35 Calcd. (%): C 50.40 H 5.92 N 23.51 IR (KBr) νmax (cm -1 ): 1630, 1596, 1557, 1393 1 H-NMR (CDCl 3 ) δ (ppm): 7.53(s, 1H), 4.16(t, 2H), 4.01(s, 3H), 2.71(s, 3H), 1.95-1.77(m, 2H), 0.98 (t, 3H) 13 H-NMR (CDCl 3 ) δ (ppm): 160.9, 154.7, 151.6, 143.3, 114.3, 45.0, 34.7, 21.2, 12.2, 11.2 Reference Example 2 3,7-Dihydro-6-methylthio-3-n-propyl-2H-purin-2-one (Compound b ) Under an argon atmosphere, 9.77 g (244 mmol) of 60% sodium hydride was washed 3 times with n-hexane. The solvent was evaporated under reduced pressure to dry. To the residue was added 900 ml of dimethylformamide. Under ice cooling, 57.0 g (271 mmol) of 3-n-propyl-6-thioxanthine (Japanese Published Unexamined Patent Application No. 183287/86) was gently added to the mixture. 15 minutes after, 15.2 ml (244 mmol) of methyl iodide was dropwise added to the reaction solution. After stirring was continued for 30 minutes, 50 ml of ethanol was added and the mixture was concentrated under reduced pressure. After 400 ml of water was added to the residue, the precipitate was collected by filtration to afford 13.9 g (yield, 23%) of Compound b as a light yellow powder. The filtrate was extracted 5 times with 200 ml of chloroform. After washing with saturated sodium chloride aqueous solution, the filtrate was dried over anhydrous sodium sulfate and the solvent was evaporated under reduced pressure. The residue was isolated and purified by silica gel column chromatography (eluting solvent; 10% methanol/chloroform) to afford further 16.0 g (yield, 26%) of Compound b as a light yellow powder. Melting point: 240.8-242.5°C IR (KBr) νmax (cm -1 ): 3400(br), 1600, 1588, 1572 1 H-NMR (DMSO-d 6 ) δ (ppm): 13.54(brs, 1H), 8.13(brs, 1H), 3.99(t, 2H), 2.57(s, 3H), 1.80-1.62(m, 2H), 0.88(t, 3H) 13 C-NMR (DMSO-d 6 ) δ (ppm): 160.6(br), 153.8, 149.4(br), 141.9(br), 112.8(br), 44.4, 20.6, 11.3, 11.0 MS (m/e): 224(M + ), 195, 182, 135 Reference Example 3 8-Cyclopentyl-3-n-propylxanthine (Compound c ) To a suspension of 5,6-diamino-1-propyl-2,4(1H, 3H)pyrimidinedione (Japanese Published Unexamined Patent Application No. 57517/80) in 600 ml of dimethylformamide were sequentially added 17.7 ml (163 mmol) of cyclopentane-carboxylic acid, 30.0 g (196 mmol) of hydroxybenzotriazole and 50.5 g (245 mmol) of dicyclohexylcarbodiimide. The mixture was stirred at room temperature overnight. Insoluble materials were filtered off and the solvent was evaporated under reduced pressure. After 600 ml of 4 N aqueous sodium hydroxide solution was added to the residue, the mixture was refluxed for 10 minutes under heating. Under ice cooling, insoluble materials were filtered off and 50 ml of methanol was added-to the filtrate. After neutralization with conc. hydrochloric acid, the precipitate was collected by filtration to afford 28.3 g (yield, 66%) of Compound c . Melting point: 311.3-313.1°C (dimethylformamide) Elemental analysis: as C 13 H 18 N 4 O 2 Found (%): C 59.56 H 6.96 N 21.69 Calcd. (%): C 59.52 H 6.92 N 21.36 IR (KBr) νmax (cm -1 ) : 3150, 2880, 1698, 1669 1 H-NMR (DMSO-d 6 ) δ (ppm): 13.05(brs, 1H), 10.94(s, 1H), 3.86(t, 2H), 3.18-3.04(m, 1H), 2.05-1.55(m, 10H), 0.87(t, 3H) 13 C-NMR (DMSO-d 6 ) δ (ppm): 157.7, 154.3, 150.9, 149.4, 106.5, 43.3, 39.0, 31.9, 25.0, 20.9, 10.9 Reference Example 4 8-Cyclopentyl-3-n-propyl-6-thioxanthine (Compound d ) A mixture of Compound c obtained in Reference Example 3 (14.1 g, 53.8 mmol) and phosphorous pentasulfide (19.5 g, 87.7 mmol) in 280 ml of pyridine was refluxed for 4 hours. The reaction mixture was poured into 600 ml of ice water and the precipitate was collected by filtration. The filtrate was concentrated under reduced pressure and the precipitate was collected by filtration again. The filtrate was combined and 400 ml of 2 N aqueous sodium hydroxide solution was added to the crystals. After insoluble materials were removed, the system was neutralized with conc. hydrochloric acid and the precipitate was collected by filtration to afford Compound d as the crude product. The crude product was recrystallized from ethanol-water to afford 13.5 g (yield, 90%) of Compound d as light yellow plates. Melting point: 214.3-215.9°C Elemental analysis: as C 13 H 18 N 4 O·1/4C 2 H 5 OH Found (%): C 56.17 H 6.76 N 19.44 Calcd. (%): C 55.93 H 6.78 N 19.33 IR (KBr) νmax (cm -1 ): 2960, 1663, 1605, 1510, 1403 1 H-NMR (DMSO-d 6 ) δ (ppm): 13.03(brs, 1H), 12.04(brs, 1H), 3.90(t, 2H), 3.30-3.10(m, 1H), 2.05-1.55(m, 10H), 0.87(t, 3H) 13 C-NMR (DMSO-d 6 ) δ (ppm): 173.3, 161.5, 148.9, 145.7, 118.5, 56.0, 43.8, 38.7, 32.0, 25.2, 20.7, 18.5, 10.9 Reference Example 5 8-Cyclopentyl-3,7-dihydro-6-methylthio-3-n-propyl-2H-purin-2-one (Compound e ) Using 6.00 g (21.6 mmol) of Compound d obtained in Reference Example 4, the procedure was performed in a manner similar to Reference Example 2 to afford 4.70 g (yield, 75%) of Compound e as a light yellow powder. Melting point: 257.5-259.2°C Elemental analysis: as C 14 H 20 N 4 OS Found (%): C 57.77 H 7.22 N 19.36 Calcd. (%): C 57.51 H 6.89 N 19.16 IR (KBr) νmax (cm -1 ): 1599, 1580, 1553, 1513 1 H-NMR (CDCl 3 , 90 MHz) δ (ppm): 4.24(t, 2H), 3.53-3.15 (m, 1H), 2.10(s, 3H), 2.50-1.50(m, 10H), 0.95 (t, 3H) Reference Example 6 8-Cyclopentyl-3,7-dihydro-7-methyl-6-methylthio-3-n-propyl-2H-purin-2-one (Compound f ) After 1.50 g (5.4 mmol) of Compound d obtained in Reference Example 4 was dissolved in 23 ml of dimethylformamide, 432 mg (10.8 mmol) of sodium hydride (60% oily) was gently added to the solution under ice cooling. The mixture was stirred for 30 minutes under ice cooling. The reaction mixture was poured into ice water and the precipitate was collected by filtration. After washing with water and then with 50% ether/hexane, 1.47 g (yield, 39%) of Compound f was obtained as a light yellow powder. 1 H-NMR (CDCl 3 , 90 MHz) δ (ppm): 4.15(t, 2H), 3.91(s, 3H), 3.20-2.95(m, 1H), 2.68(s, 3H), 2.20-1.50(m, 10H), 0.90(t, 2H) Reference Example 7 3,7-Dihydro-6-methylthio-8-(noradamantan-3-yl)-3-n-propyl-2H-purin-2-one (Compound g ). After 10 g of (30.3 mmol) of 8-(Noradamantan-3-yl)-3-n-propyl-6-thioxanthine was suspended in 90 ml of water, 30 ml of 2 N aqueous sodium hydroxide solution and 60 ml of ethanol were added to the suspension. Under stirring, 2.83 ml (45.5 mmol) of methyliodide was dropwise added to the mixture. After stirring for 1 hour, the mixture was neutralized and extracted 3 times with chloroform. The extracts were combined, and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure to afford 9.81 g (yield, 94%) of Compound g as an amorphous powder. 1 H-NMR (CDCl 3 , 90 MHz) δ (ppm): 13.3(brs, 1H), 4.23 (t, 2H), 2.80(t, 1H), 2.50-1.45(m, 14H), 1.95(s, 3H), 0.96(t, 3H) Reference Example 8 8-Dicyclopropylmethyl-3,7-dihydro-6-methylthio-3-n-propyl-2H-purin-2-one (Compound h ). Using 2.33 g (7.66 mmol) of 8-dicyclopropylmethyl-3-n-propyl-6-thioxanthine, the procedure was performed in a manner similar to Reference Example 10 to afford 2.76 g (quantitative) of Compound h as a light yellow powder. 1 H-NMR (CDCl 3 , 90 MHz) δ (ppm): 4.23(t, 2H), 2.10-0.10 (m, 13H), 1.93(s, 3H), 0.93(t, 3H) Reference Example 9 3-n-Propyl-8-styryl-6-thioxanthine (Compound i), After 4.14 g (14.0 mmol) of 3-n-propyl-8-styryl-xanthine was suspended in 80 ml of pyridine, 5.07 g (22.8 mmol) of phosphoruspentasulfide was added to the suspension, and the mixture was refluxed for 2.5 hours under heating. After the mixture was poured into 300 ml of an ice water, a precipitate was collected by filtration, and suspended in 150 ml of 2 N sodium hydroxide. The suspension was stirred for 30 minutes at room temperature and insoluble matters were removed by filtration. A filtrate was neutralized, and a precipitate was collected by filtration to afford 4.25 g (yield, 97%) of Compound i as a yellow powder. Melting point: >290°C (dioxane-water) Elemental analysis: as C 16 H 16 N 4 OS·1/2C 4 H 8 O 2 Found (%): C 60.60 H 5.65 N 15.73 Calcd. (%): C 60.65 H 5.65 N 15.72 IR (KBr) νmax (cm -1 ): 1689, 1604, 1511 1 H-NMR (DMSO-d 6 , 90 MHz) δ (ppm): 7.85(d, J=16.0Hz, 1H), 7.70-7.35(m, 5H), 7.20(d, J=16.0Hz, 1H), 3.99(t, 2H), 2.00-1.65(m, 2H), 0.93(t, 3H) MS (m/e, relative intensity): 312(M + , 100), 269(35), 252(18) Reference Example 10 3,7-Dihydro-7-methyl-6-methylthio-3-n-propyl-8-styryl-2H-purin-2-one (Compound j ). Using 2.00 g (6.41 mmol) of Compound i obtained in Reference Example 9, the procedure was performed in a manner similar to Reference Example 1 to afford 1.73 g (yield, 79%) of Compound j as a light yellow powder. 1 H-NMR (CDCl 3 , 90 MHz δ (ppm): 7.91(d, J=15.5Hz, 1H), 7.70-7.35(m, 5H), 6.92(d, J=15.5Hz, 1H), 4.20 (t, 2H), 4.04(s, 3H), 2.70(s, 3H), 2.10-1.70(m, 2H), 1.02(t, 3H) Preparation Example 1 Tablet Tablet comprising the following composition is prepared in a conventional manner. Compound 6 20 mg Lactose 60 mg Potato starch 30 mg Polyvinyl alcohol 3 mg Magnesium stearate 1 mg Reference Example 14 2-Benzylthio-9-trityl-1,7-dihydro-6H-purin-6-one (Compound o ) 2.00 g (11.9 mmol) of 2-mercapto-6-hydroxypurine was dissolved in a solvent mixture of 10 ml of ethanol, 10.9 ml of 2 N sodium hydroxide and 15 ml of water. Under ice cooling with stirring, 2.06 ml (17.9 mmol) of benzylbromide was added to the solution, following stirring at room temperature for 30 minutes. Again under ice cooling, the mixture was neutralized with 2 N hydrochloric acid and 30 ml of n-hexane was added to the mixture. A precipitated was collected by filtration, washed with ethyl acetate and dried to afford 1.32 g (yield, 45%) of 2-benzylthio-6-hydroxypurine as a crude product. 1.00 g (3.88 mmol) of 2-benzylthio-6-hydroxypurine was dissolved in 20 ml of dimethylformamide and 0.816 ml (5.82 mmol) of triethylamine was added to the solution. Under ice cooling, 1.62 g (5.82 mmol) of tritylchloride was added to the mixture following stirring at room temperature overnight. After 400 ml of water was added, a precipitate was collected by filtration and washed with n-hexane and with ethyl acetate. Recrystallization from ethanol afforded 0.785 g (yield, 40%) of Compound o as a white powder. Melting point: 267-270°C Elemental analysis: as C 31 H 24 N 4 OS Found (%): C 74.33 H 4.87 N 11.30 Calcd. (%): C 74.38 H 4.83 N 11.19 IR (KBr) νmax (cm -1 ): 1683, 1554 1 H-NMR (CDCl 3 , 90 MHz) δ (ppm): 7.76(s, 1H), 6.75-7.61 (m, 20H), 4.38(s, 2H) MS (m/e): 260(M + -C 6 H 5 X 3 +1) Reference Example 15 2-Benzylthio-1-methyl-9-trityl-1,7-dihydro-6H-purin-6-one (Compound p ) After 500 mg (0.10 mmol) of Compound o obtained in Reference Example 14 was dissolved in 20 ml of tetrahydrofuran, 0.08 g (0.20 mmol) of 60% sodium hydroxide was added to the solution under ice cooling. After 30 minutes, 0.125 ml (0.20 mmol) of methyliodide was added, and the mixture was stirred for 2 hours at 50°C. The solvent was evaporated under reduced pressure, and water was added to the residue. The mixture was extracted with chloroform, and the extract was washed with a saturated aqueous sodium chloride, dried over anhydrous sodium sulfate and filtered. The solvent was evaporated under reduced pressure, and the residue was purified by silicagelcolumchromatography (eluent: chloroform) to afford 300 mg (yield, 58%) of Compound p as a white powder. Melting point: 255-258°C (isopropanol-water) Elemental analysis: as C 32 H 26 N 4 OS Found (%): C 75.00 H 5.11 N 10.96 Calcd. (%): C 74.68 H 5.09 N 10.89 IR (KBr) νmax (cm -1 ): 1700, 1555 1 H-NMR (CDCl 3 ) δ (ppm): 7.64(s, 1H), 7.07-7.46(m, 18H), 6.94-6.98(m, 2H), 3.49(s, 3H), 3.48(s, 2H) Reference Example 16 2-Chloro-8-(noradamantan-3-yl)-1-n-butyl-7-methyl-1,7-dihydro-6 H -purin-6-one The procedure is performed in a manner similar to Reference Example 9 except for using 2-chloro-8-(noradamantan-3-yl)-7-methyl-1,7-dihydro-6 H -purin-6-one to afford the captioned compound. Reference Example 17 2-Chloro-8-dicyclopropylmethyl-1-n-butyl-7-methyl-1,7-dihydro-6 H -purin-6-one The procedure is performed in a manner similar to Reference Example 9 except for using 2-chloro-8-dicyclopropylmethyl-7-methyl-1,7-dihydro-6 H -purin-6-one to afford the captioned compound. Reference Example 18 2-Chloro-8-styryl-1-n-butyl-7-methyl-1,7-dihydro-6 H -purin-6-one The procedure is performed in a manner similar to Reference Example 9 except for using 2-chloro-8-styryl-7-methyl-1,7-dihydro-6 H -purin-6-one to afford the captioned compound. Reference Example 19 2-Benzylthio-8-(noradamantan-3-yl)-9-trityl-1,7-dihydro-6 H -purin-6-one The procedure is performed in a manner similar to Reference Example 14 except for using 8-(noradamantan-3-yl)-2-mercapto-6-hydroxypurin to afford the captioned compound. Reference Example 20 2-Benzylthio-8-dicyclopropylmethyl-9-trityl-1,7-dihydro-6 H -purin-6-one The procedure is performed in a manner similar to Reference Example 14 except for using 8-dicyclopropylmethyl-2-mercapto-6-hydroxypurin to afford the captioned compound. Reference Example 21 2-Benzylthio-8-styryl-9-trityl-1,7-dihydro-6 H -purin-6-one The procedure is performed in a manner similar to Reference Example 14 except for using 8-styryl-2-mercapto-6-hydroxypurin to afford the captioned compound. Reference Example 22 2-Benzylthio-1-methyl-8-(noradamantan-3-yl)-9-trityl-1,7-dihydro-6 H -purin-6-one The procedure is performed in a manner similar to Reference Example 15 using the compound obtained in Reference Example 19 to afford the captioned compound. Reference Example 23 2-Benzylthio-8-dicyclopropylmethyl-1-methyl-9-trityl-1,7-dihydro-6 H -purin-6-one The procedure is performed in a manner similar to Reference Example 15 using the compound obtained in Reference Example 20 to afford the captioned compound. Reference Example 24 2-Benzylthio-1-methyl-8-styryl-9-trityl-1,7-dihydro-6 H -purin-6-one The procedure is performed in a manner similar to Reference Example 15 using the compound obtained in Reference Example 21 to afford the captioned compound. Preparation Example 1 Tablet Tablet comprising the following composition is prepared in a conventional manner. Compound 6 20 mg Lactose 60 mg Potato starch 30 mg Polyvinyl alcohol 3 mg Magnesium stearate 1 mg

Claims: A condensed purin derivative represented by the formula (I): in which R 3 represents hydrogen or C 1 -C 6 alkyl or benzyl, each of X 1 and X 2 independently represents hydrogen, C 1 -C 6 alkyl, C 7 -C 15 aralkyl or phenyl; R 1 represents hydrogen, C 1 -C 6 alkyl, C 3 -C 6 cycloalkyl, noradamantan-3-yl, dicyclopropylmethyl or styryl; and R 2 represents hydrogen or C 1 -C 6 alkyl or C 3 -C 6 cycloalkyl; or a pharmaceutically acceptable salt thereof. The compound according to Claim 1, wherein R 1 represents hydrogen, C 3 -C 6 cycloalkyl, noradamantan-3-yl, dicyclopropylmethyl or styryl; R 2 represents hydrogen or C 1 -C 6 alkyl; R 3 represents C 1 -C 6 alkyl; X 1 represents hydrogen, C 1 -C 6 alkyl, aralkyl or phenyl; and X 2 represents hydrogen, phenyl or C 1 -C 6 alkyl. The compound according to Claim 2, wherein both of X 1 and R 1 are hydrogen. The compound according to Claim 2, wherein X 1 is ethyl and X 2 is hydrogen. A compound which is selected from 1-methyl-7-phenyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo [2,1-i] purin-5-one;7-phenyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one;2-cyclopentyl-8-ethyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i]purin-5-one; 8-ethyl-2-(noradamantan-3-yl)-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i] purin-5-one;2-(dicyclopropylmethyl)-8-ethyl-4-n-propyl-1,4,7,8-tetrahydro-5H-imidazo-[2,1-i] purin-5-one;8-ethyl-1-methyl-4-n-propyl-2-styryl-1,4,7,8-tetrahydro-5H-imidazo[2,1-i] purin-5-one and a pharmaceutically acceptable salt thereof. A compound according to Claim 1 or 5, wherein said salt is selected from the group consisting of a pharmaceutically acceptable acid addition salt, a metal salt, an ammonium salt, an organic amine addition salt and an amino acid addition salt. A pharmaceutical composition comprising a pharmaceutical carrier and as an active ingredient, an effective amount of the compound as defined by Claim 1 or 5. A condensed purine derivative of the formula I according to any one of claims 1 to 6 for use as a therapeutically active agent. A condensed purine derivative of the formula I according to any one of claims 1 to 6 for use as diuretic agent, renal protecting agent, bronchodilatory agent or hypotensive agent. Method for the preparation of a compound according to any one of claims 1 to 5, comprising reacting a compound of formula (IV) with a halogenating agent or an inorganic acid in the presence or absence of a solvent. Method for the preparation of a compound according to any one of claims 1 to 5, wherein R 2 is other than hydrogen, comprising reacting a compound of formula (I), wherein R 2 is hydrogen with a compound (XI) represented by the following formula in the presence or absence of a base R 2a -Z wherein Z represents the leaving group and R 2a has the same significance as that of R 2 except for hydrogen. Method for the preparation of a pharmaceutical composition, comprising combining an effective amount of a compound according to any one of claims 1 to 5 as an active ingredient and an pharmaceutically acceptable carrier.

Inventors: KARASAWA AKIRA, KUBO KAZUHIRO, KURODA TAKESHI, OHMORI KENJI, OHNO TETSUJI, SHIMADA JUNICHI, SUZUKI FUMIO, KARASAWA, AKIRA, KUBO, KAZUHIRO, KURODA, TAKESHI, OHMORI, KENJI, OHNO, TETSUJI, SHIMADA, JUNICHI, SUZUKI, FUMIO
Applicants: KYOWA HAKKO KOGYO KK, KYOWA HAKKO KOGYO KABUSHIKI KAISHA
Application year: 1990
Main classification: C07D487
IPC codes: C07D487, A61K31, A61P7, A61P9, A61P13, A61P15, A61P11, C07D471