Abstract:
Disclosed are naphthyridine derivatives represented by formula (I) ##STR1## wherein: X represents hydrogen; lower alkyl; aralkyl; substituted or unsubstituted aryl; substituted or unsubstituted aromatic heterocyclic group; --NR 1  R 2  wherein R 1  and R 2  independently represent hydrogen or lower alkyl; ##STR2##  wherein W represents N or CH, Z represents a single bond, oxygen or NR 3  (wherein R 3  represents hydrogen, lower alkyl or benzyl) and n1 and n2 represent an integer of 1 to 3; or substituted or unsubstituted thiazolinyl; and 
     Y is a single bond or alkylene and pharmaceutically acceptable salts thereof. The compounds show potent anti-inflammatory activity and are expected to be useful in treating rheumarthritis.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to novel 1,8-naphthyridin-2-one derivatives having an anti-inflammatory activity and which are useful for the treatment of rheumarthritis. 
     Rheumarthritis, which is characterized by inflammation and pain of articulations, shows a morbidity rate of 3-4%. While pathogenesis of rheumarthritis is not fully clarified, steroid type and non-steroid type anti-inflammatory agents have been used for therapy of rheumarthritis. In contrast to other non-steroid type anti-inflammatory agents, piroxicam (U.S. Pat. No. 3,591,584) and RU-43526 [J. Med. Chem., 31, 1453 (1988)] have no carboxylic acid moiety. ##STR3## 
     As to 4-hydroxy-1,8-naphthyridin-2-one derivatives, the following compounds represented by formula (A) are disclosed. ##STR4## 
     (1) A compound of formula (A) wherein R A  is phenyl and R B  is nitro having anti-allergic activity (Japanese Published Unexamined Patent Application No. 36694/77). 
     (2) A compound of formula (A) wherein R A  is phenyl and R B  is butyl having anti-ulcer activity (Sch 12223) [J Pharm. Exp. Ther., 246, 578 (1988)]. 
     (3) Compounds of formula (A) wherein R A  is alkyl, aralkyl, or the like and R B  is carbamoyl, N-alkylcarbamoyl, N-alkoxycarbamoyl, or the like having anti-ulcer activity (U S. Pat. No. 4,215,123). 
     (4) Compounds of formula (A) wherein R A  is alkyl or the like and R B  is ethoxycarbonyl [J. Med. Chem., 30, 2270, (1987)]. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide novel naphthyridine derivatives having potent anti-inflammatory activity. 
     The present invention relates to naphthyridine derivatives represented by general formula (I): ##STR5## wherein X represents hydrogen; lower alkyl; aralkyl; substituted or unsubstituted aryl; substituted or unsubstituted aromatic heterocyclic group; --NR 1  R 2  wherein R 1  and R 2  independently represent hydrogen or lower alkyl; ##STR6## wherein W represents N or CH, Z represents a single bond, oxygen or NR 3  (wherein R 3  represents hydrogen, lower alkyl or benzyl), and n1 and n2 represent an integer of 1 to 3 or substituted or unsubstituted thiazolinyl; and Y is a single bond or alkylene and pharmaceutically acceptable salts thereof. 
     The compounds represented by formula (I) are hereinafter referred to as Compounds (I); the same applies to the compounds of other formula numbers. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the definitions of the groups in formula (I), the lower alkyl means a straight-chain or branched alkyl group having 1 to 6 carbon atoms, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl and hexyl. The aralkyl means an aralkyl group having 7 to 20 carbon atoms, for example, benzyl, phenethyl, benzhydryl and trityl. The aryl means an aryl group having 6 to 10 carbon atoms such as phenyl and naphthyl. Examples of the aromatic heterocyclic group include pyridyl, pyrimidinyl, thiazole and benzothiazole. The alkylene means a straight-chain or branched alkylene group having 1 to 6 carbon atoms such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, ethylethylene and propylene. The aryl, the aromatic heterocyclic group and the thiazolinyl may be substituted by 1 to 2 substituents which are the same or different. Examples of the substituents are lower alkyl, lower alkoxy, halogen, nitro, and amino. The lower alkyl and the alkyl moiety in the lower alkoxy are the same as defined for the lower alkyl described above. Examples of the halogen include fluorine, chlorine, bromine and iodine. 
     The pharmaceutically acceptable salts of Compounds (I) include acid addition salts, metal salts, ammonium salts, organic amine addition salts, and amino acid addition salts. 
     As the pharmaceutically acceptable acid addition salts of Compounds (I), inorganic acid addition salts such as hydrochloride, sulfate and phosphate, and organic acid addition salts such as acetate, maleate, fumarate, tartrate and citrate may be mentioned. As the pharmaceutically acceptable metal salts, alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as magnesium salt and calcium salt, aluminum salt, and zinc salt may be mentioned. As the pharmaceutically acceptable organic amine addition salts, salts with morpholine and piperidine may be mentioned, and as the pharmaceutically acceptable amino acid addition salts, salts with lysine, glycine and phenylalanine may be mentioned. 
     The processes for preparing Compounds (I) are described below. 
     In the following processes, in cases where the defined groups change under the conditions shown or are inappropriate for practicing the processes, the processes can be readily carried out by applying thereto means conventionally used in organic synthetic chemistry, for example, protection of functional groups and elimination of protecting groups. 
     Process 1 
     Compound (I) can be obtained by allowing Compound (II) to react with Compound (III), if necessary, in the presence of a base. ##STR7## In the above formulae, R 3  represents lower alkyl; and X and Y have the same significances as defined above. 
     The lower alkyl in formula (II) has the same significance as the lower alkyl described above. 
     Examples of the base are alkali metal carbonates such as potassium carbonate and sodium carbonate, alkali metal hydrides such as sodium hydride, alkali metal alkoxides such as sodium methoxide and sodium ethoxide, and alkylamines such as triethylamine. 
     As a reaction solvent, those which are inert to the reaction, for example, ethers such as tetrahydrofuran and dioxane, amides such as dimethylformamide, alcohols such as methanol and ethanol, hydrocarbons such as xylene, toluene, hexane and cyclohexane, halogenated hydrocarbons such as chloroform and carbon tetrachloride, and dimethylsulfoxide may be used alone or in combination. 
     The reaction is carried out at 0° to 300° C. and is completed in 10 minutes to 24 hours. 
     Compound (II) can be obtained in accordance with the following reaction steps shown as Processes A and B. ##STR8## In the above formulae, R 3  has the same significance as defined above; and the definition of R 3a  is the same as R 3 . 
     The starting Compound (IV) can be synthesized by a known method [J. Org. Chem., 39, 1803 (1974)] or by its modification. 
     Step 1 
     Compound (V) can be obtained by allowing Compound (IV) to react with phosgene, triphosgene or trichloromethyl chloroformate (TCF), if necessary, in a solvent. 
     As the reaction solvent, those which are inert to the reaction, for example, ethers such as tetrahydrofuran and dioxane, hydrocarbons such as toluene and hexane, and halogenated hydrocarbons such as 1,2-dichloroethane and chloroform may be used alone or in combination. 
     The reaction is carried out at 0° to 200° C. and is completed in 5 minutes to 24 hours. 
     Step 2 
     Compound (II) can be obtained by allowing Compound (V) to react with Compound (VI), in the presence of a base, and if necessary, in a solvent. 
     The reaction is carried out under the same conditions using the same solvent and base as in Step 1. ##STR9## In the above formulae, Hal represents chlorine, bromine or iodine; and R 3  and R 3a  have the same significances as defined above. 
     Step 3 
     Compound (VII) can be obtained by allowing Compound (IV) to react with Compound (VIII) in the presence of a base, and if necessary, in a solvent. 
     The reaction is carried out under the same conditions using the same solvent and base as in Step 1. 
     Step 4 
     Compound (II) can be obtained by treating Compound (VII) with a base, if necessary, in a solvent. 
     The reaction is carried out under the same conditions using the same solvent and base as in Step 1. 
     Process 2 
     Compound (I) can also be obtained by the following reaction steps. ##STR10## In the above formulae, R 3  has the same significance as defined above. 
     Step 5 
     Compound (IX) can be obtained by heating Compound (II) in a solvent in the presence of an alkali. 
     As the alkali, alkali metal hydroxides such as sodium hydroxide, alkali metal carbonates such as potassium carbonate, alkali metal bicarbonates such as potassium bicarbonate, etc. may be used. 
     As the reaction solvent, water, alcohols such as methanol and ethanol, ethers such as tetrahydrofuran and dioxane, etc. may be used alone or in combination. 
     The reaction is carried out at 30° to 200° C. and is completed in 5 minutes to 24 hours. 
     Step 6 
     Compound (I) can be obtained by allowing Compound (IX) to react with Compound (X) represented by formula (X): 
     
         X--Y--N═C═O                                        (X) 
    
     (wherein X and Y have the same significances as defined above), if necessary, in the presence of a base. 
     The reaction is carried out under the same conditions using the same solvent and base as in Process 1. 
     Process 3 
     Compound (I) can also be prepared according to the following reaction step. ##STR11## In the above formula, the definition of R 3b  is the same as R 3  ; and X and Y have the same significances as defined above. 
     Compound (I) can be obtained by allowing Compound (V) to react with Compound (XI) in the presence of a base. 
     The reaction is carried out under the same conditions using the same solvent and base as in Process 1. 
     The intermediates and the desired products in the processes described above can be isolated and purified by purification means conventionally used in organic synthetic chemistry, for example, filtration, extraction, washing, drying, concentration, recrystallization and various kinds of chromatography. The intermediates can be subjected to the subsequent reaction without particular purification. 
     In the case where a salt of Compound (I) is desired and it is produced in the form of the desired salt, it can be subjected to purification as such. In the case where Compound (I) is produced in the free state and its salt is desired, it can be converted into its salt in a conventional manner. 
     Compounds (I) and pharmaceutically acceptable salts thereof sometimes exist in the form of an addition product with water or with a solvent. Such addition products are also included within the scope of the present invention. 
     Specific examples of Compounds (I) are shown in Table 1. The compound numbers in the table respectively correspond to the numbers of Examples described below. 
     
                       TABLE 1______________________________________ ##STR12##Compound No.   YX______________________________________1              (CH.sub.2).sub.3 CH.sub.32              CH.sub.3           ##STR13##4           ##STR14##5           ##STR15##6              N(CH.sub.3).sub.2 7             CH.sub.2 CH.sub.2 N(CH.sub.3).sub.2 8           ##STR16## 9           ##STR17##10           ##STR18##11           ##STR19##12           ##STR20##13           ##STR21##14           ##STR22##15           ##STR23##16           ##STR24##17           ##STR25##18           ##STR26##19           ##STR27##20           ##STR28##21           ##STR29##22           ##STR30##23           ##STR31##24           ##STR32##25           ##STR33##26           ##STR34##27           ##STR35##28           ##STR36##29           ##STR37##30           ##STR38##31           ##STR39##32           ##STR40##______________________________________ 
    
     The pharmacological activities of Compounds (1) are illustrated below. 
     a) Effect on carrageenin-induced paw edema 
     Male Wistar rats weighing 150 to 160 g (n=3-5) were used in the experiment. After the right hind paw volume was measured with the plethysmograph (TK-101; Unicom Co., Ltd.), the test compound (100 mg/kg) was orally administered. After one hour, 0.1 ml of 1 % carrageenin (λ-carrageenin; PICNIN-A®, Zushi Kagaku Co., Ltd.) was subcutaneously injected into the right hind paw footpad. Three hours after the injection of carrageenin, the right hind paw volume was measured and the swelling rate was determined by the following equation 1. ##EQU1## 
     Vt: the right hind paw volume measured 3 hours after the injection of carrageenin 
     Vo: the right hind paw volume measured prior to the injection of carrageenin 
     The suppression rate was calculated by the following equation 2. ##EQU2## 
     Swt: the swelling rate of the group administered with the test compound 
     Swc: the swelling rate of the control group administered with no test compound 
     The results are shown in Table 2. 
     b) Effect on zymosan-induced paw edema 
     The experiment was carried out in the same manner as in the carrageenin-induced paw edema test except that 1% zymosan (Zymosan A®; Sigma Chemical Co.) was used in place of 1% carrageenin and the right hind paw volume was measured 4 hours after the injection of the edema-inducing substance instead of 3 hours. The swelling rate and the suppression rate were calculated by equation 1 and equation 2, respectively. The results are shown in Table 2. 
     c) Arachidonic acid-induced paw edema 
     The experiment was carried out in the same manner as in the carrageenin-induced paw edema test except that 0.5% arachidonic acid was used in place of 1% carrageenin and the right hind paw volume was measured one hour after the injection of the edema-inducing substance instead of 3 hours. The swelling rate and the suppression rate were calculated by equation 1 and equation 2, respectively. The results are shown in Table 2. 
     
                       TABLE 2______________________________________Suppression rate for paw swelling (%)   (a)         (b)       (c)   Carrageenin-               Zymosan-  Arachidonic acid-   induced     induced   inducedCompound   edema       edema     edema______________________________________1                   20.54       40.0        37.8      34.95       38.5        38.4      48.06       31.7        27.37       23.29       25.219      34.222                            33.423      22.7        22.228      27.3                  41.629                            33.3______________________________________ 
    
     d) Effect on Type III allergic reaction-induced pleurisy 
     1. Preparation of IgG fraction of rabbit anti-egg white albumin (anti-OA) 
     IgG was purified from rabbit anti-OA serum prepared in advance by the method of Koda et al. [Folia Pharmacol., Japon 66, 237, (1970)] in the following manner. 
     A saturated solution of ammonium sulfate (half volume of the serum) was added to the anti-OA serum, and the mixture was left for one hour at 4° C. The precipitate was taken by centrifugation (3,000 rpm, 30 min, 4° C.) and dissolved in phosphate buffered saline of Dulbecco. Then, ammonium sulfate fractionation was carried out three times in the same manner as above, whereby a purified IgG fraction was obtained. 
     2. Type III allergic reaction-induced pleurisy 
     Male Wistar rats weighing 225-250 g were pre-bred for several days and fasted overnight prior to the experiment The test compound (100 mg/kg) was orally administered to the animals, and after 30 minutes, IgG of rabbit anti-OA (0.2 ml, 5 mg protein/ml) was injected into the pleural cavity of the animals under anesthesia with ether. Thirty minutes after the injection of IgG, OA (albumin egg grade III; Sigma Chemical Co.) was intravenously injected into the animals as an inducer of pleurisy. After two hours, Evans Blue (25 mg/kg) was intravenously injected, and four and a half hours after the induction of pleurisy, the animals were killed by bleeding. 
     Then, an exudate in the pleural cavity was obtained, and the volume of the exudate was measured. The pleural cavity was rinsed with 5 ml of physiological saline and the rinsings were added to the exudate. The number of infiltrated cells in the mixture was counted and the volume of the dye in the mixture was determined by the absorption at 625 nm [Agent Actions., 25, 326 (1988)]. The suppression rates for the volume of the exudate, the number of infiltrated cells and the volume of the dye in the pleural cavity were calculated by the following equation 3. ##EQU3## 
     S.V: the value obtained with the group administered with the test compound and in which pleurisy is induced 
     N.V: the value obtained with the group in which pleurisy is not induced 
     P.V: the value obtained with the group administered with no test compound and in which pleurisy is induced 
     The results are shown in Table 3 
     
                       TABLE 3______________________________________    Suppression rate (%)                Volume of   Number of      Volume of dye in the  infiltrated cellsCompound   exudate   exudate     in the exudate______________________________________2          27.2      28.34          75.3      54.4        30.55          100.0     66.5        58.68                                21.79          27.3                  28.511         22.1      37.212                   24.013         28.9      25.816                               25.417         22.4                  21.518         26.9                  22.119                               26.821         32.4      50.2        22.122         89.2      51.0        34.623         24.0      43.2        26.724         29.7      32.127                   23.6______________________________________ 
    
     e) Acute toxicity 
     The test compounds were orally or intraperitoneally administered to male dd-mice weighing 20 to 25 g. MLD (Minimum Lethal Dose) was determined by observing the mortality for seven days after the administration. 
     The results are shown in Table 4. 
     
                       TABLE 4______________________________________          Acute toxicity (MLD: mg/kg)Compound         p.o.    i.p.______________________________________4                &gt;300    &gt;1005                 300    &gt;1006                &gt;300    &gt;1007                &gt;300    &gt;1009                &gt;300    &gt;10011               &gt;300    &gt;10019               &gt;300    &gt;10022               &gt;300    &gt;10023               &gt;300    &gt;10028               &gt;300    &gt;10029               &gt;300    &gt;100______________________________________ 
    
     It is considered that the tissue disturbance caused by immunocomplex (Type III allergy reaction) is one of the pathogenetic factors for rheumarthritis. Hence, the above results suggest that Compounds (I) will be effective for the therapy of rheumarthritis by the suppression effects on both inflammation and Type III allergic reaction. 
     Compounds (I) and pharmaceutically acceptable salts thereof may be used as they are or in various preparation forms. The pharmaceutical composition of the present invention can be prepared by uniformly mixing Compound (I) or a pharmaceutically acceptable salt thereof as the active ingredient in an effective amount, with pharmaceutically acceptable carriers. These pharmaceutical compositions are desirably in a single dose unit which is suited for oral or parenteral administration. 
     In preparing the composition for oral administration, any pharmaceutically acceptable carriers may be used according to the preparation form. For example, liquid preparations such as a suspension and a syrup may be prepared using water; sugars such as sucrose, sorbitol and fructose; glycols such as polyethylene glycol and propylene glycol; oils such as sesame oil, olive oil and soybean oil; preservatives such as p-hydroxybenzoic acid esters; flavors such as strawberry flavor and peppermint, etc. Powders, pills, capsules and tablets may be prepared using excipients 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; plasticizers such as glycerine, etc. Tablets and capsules are the most useful single dose units for oral administration since their administration is easy. 
     A solution for parenteral administration may be prepared using carriers such as distilled water, a saline solution, a glucose solution, and a mixture of a saline solution and a glucose solution. 
     The effective dose and the administration schedule of Compounds (I) or pharmaceutically acceptable salts thereof vary depending upon mode of administration, age, body weight and conditions of a patient, etc., but it is generally preferred to administer the effective compound in a dose of 1 to 1,000 mg/person/day atone time or in 2 to 3 parts. 
     Certain embodiments of the invention are illustrated in the following examples. 
     EXAMPLE 1 
     N-(n-Butyl)-4-hydroxy-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 1) 
     Xylene (30 ml) was added to 7.5 g (0.0051 mol) of Compound IIa obtained in Reference Example 2 and 0.27 ml (0.015 mol) of n-butylamine, and the mixture was heated to reflux for 2 hours. The resulting solution was cooled to room temperature and the precipitate was taken by filtration. After 150 ml of ethyl acetate was added to the precipitate and the mixture was stirred for one hour, the resulting crystals were taken by filtration. Recrystallization from ethanol-water gave 1.1 g (yield 62%) of Compound 1 as colorless crystals. 
     Melting point: 181-184° C. (ethanol-water) 
     MS (EI) m/e: 337(M + ), 294, 265 
     NMR (CF 3  COOD) δ (ppm): 9.40(1H, dd, J=8, 2 Hz), 8.62 (1H, dd, J=4, 2 Hz), 7.75-7.96(4H, m), 7.43-7.62 (2H, m), 3.63(2H, t, J=7 Hz), 1.65-1.84(2H, m), 1.40-1.57(2H, m), 1.04(3H, t, J=7 Hz) 
     IR (KBr) cm -1  : 1622, 1554 
     Elemental analysis (%): C 19  H 19  N 3  O 3   
     Calcd. C 67.64, H 5.67, N 12.45. 
     Found C 67.83, H 5.96, N 12.40. 
     EXAMPLE 2 
     4-Hydroxy-N-methyl-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 2) 
     Compound 2 was obtained in the same manner as in Example 1 except for the use of methylamine instead of n-butylamine (yield 70%). 
     Melting point: &gt;300° C. (ethanol) 
     MS (EI) m/e: 295(M + ), 294, 263, 168 
     NMR (CF 3  COOD) δ (ppm): 9.40(1H, dd, J=8, 2 Hz), 8.63 (1H, dd, J=6, 2 Hz), 7.73-7.94(4H, m), 7.45-7.58 (2H, m) 
     IR (KBr) cm 31  1 : 1629, 1595, 1553 
     Elemental analysis (%): C 16  H 13  N 3  O 3   
     Calcd.: C 65.08, H 4.44, N 14.23. 
     Found : C 65.29, H 4.26, N 14.184. 
     EXAMPLE 3 
     N-Benzyl-4-hydroxy-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 3) 
     Compound 3 was obtained in the same manner as in Example 1 except for the use of benzylamine instead of n-butylamine (yield 66%). 
     Melting point: 219-222° C. (dimethylsulfoxide-water) 
     MS (EI) m/e: 371(M + ), 265 
     NMR (CF 3  COOD) δ (ppm): 9.40(1H, dd, J=8, 2 Hz), 8.63 (1H, dd, J=4, 2 Hz), 7.90(1H, dd, J=8, 4 Hz), 7.75-7.86(3H, m), 7.46-7.58(2H, m), 7.30-7.46 (5H, m), 4.77(2H, s) 
     IR (KBr) cm -1  : 1627, 1582, 1549 
     Elemental analysis (%): C 22  H 17  N 3  O 3   
     Calcd.: C 71.15, H 4.61, N 11.31. 
     Found: C 71.54, H 4.62, N 11.22. 
     EXAMPLE 4 
     4-Hydroxy-2-oxo-1-phenyl-N-(3-pyridyl)-1H-1,8-naphthyridine-3-carboxamide (Compound 4) 
     Compound 4 was obtained in the same manner as in Example 1 except for the use of 3-aminopyridine instead of n-butylamine (yield 74%). 
     Melting point: &gt;300° C. (dimethylsulfoxide) 
     MS (EI) m/e: 358(M + ), 265, 94 
     NMR (CF 3  COOD) δ (ppm): 9.76(1H, d, J=2 Hz), 9.47(1H, dd, J=8, 2 Hz), 8.88-8.93(1H, m), 8.74(1H, dd, J=6, 2 Hz), 8.67(1H, d, J=6 Hz), 8.16(1H, dd, J=8, 6 Hz), 7.90(1H, dd, J=8, 6 Hz), 7.75-7.92(3H, m), 7.53-7.57(2H, m) 
     IR (KBr) cm -1  : 1658, 1620, 1542 
     Elemental analysis (%): C 20  H 14  N 4  O 3 .0.3H 2  O 
     Calcd.: C 66.04, H 4.05, N 15.40. 
     Found: C 66.21, H 3.92, N 15.16. 
     EXAMPLE 5 
     4-Hydroxy-2-oxo-1-phenyl-N-(4-pyridyl)-1H-1,8-naphthyridine-3-carboxamide (Compound 5) 
     Compound 5 was obtained in the same manner as in Example 1 except for the use of 4-aminopyridine instead of n-butylamine (yield 51%). 
     Melting point: &gt;300° C. (dimethylsulfoxide) 
     MS (EI) m/e: 358M + ), 357, 265, 263 
     NMR (CF 3  COOD) δ (ppm): 9.47(1H, d, J=8 Hz), 8.75(1H, d, J=6 Hz), 8.70(2H, d, J=7 Hz), 8.53(2H, d, J=7 Hz), 7.99(1H, dd, J=8, 6 Hz), 7.79-7.93(3H, m), 7.49-7.59(2H, m) 
     IR (KBr) cm -1  : 1687, 1589, 1503 
     Elemental analysis (%): C 20  H 14  N 4  O 3 .0.6H 2  O 
     Calcd.: C 65.07, H 4.15, N 15.17. 
     Found: C 65.22, H 3.85, N 14.93. 
     EXAMPLE 6 
     N-Dimethylamino-4-hydroxy-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 6) 
     Compound 6 was obtained in the same manner as in Example 1 except for the use of N,N-dimethylhydrazine instead of n-butylamine (yield 57%). 
     Melting point: 239-240° C. (isopropyl alcohol-water) 
     MS (EI) m/e: 324(M + ), 265, 263 
     NMR (CDCl 3 ) δ (ppm): 17.36(1H, s), 10.74(1H, s), 8.51-8.59(2H, m), 7.49-7.64(3H, m), 7.20-7.32 (3H, m), 2.67(6H, s) 
     IR (KBr) cm -1  : 1626, 1548 
     Elemental analysis (%): C 17  H 16  N 4  O 3   
     Calcd.: C 62.95, H 4.97, N 17.27. 
     Found: C 63.19, H 5.01, N 17.09. 
     EXAMPLE 7 
     N-(2-Dimethylaminoethyl)-4-hydroxy-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 7) 
     Compound 7 was obtained in the same manner as in Example 1 except for the use of N,N-dimethylaminoethylamine instead of n-butylamine (yield 66%). 
     Melting point: 240-242° C. (ethanol) 
     MS (EI) m/e: 352(M + ), 265, 58 
     NMR (CDCl 3 ) δ (ppm): 17.50-17.77(1H, brs), 10.09(1H, brs), 8.49-8.56(2H, m), 7.47-7.62(3H, m), 7.21-7.29(3H, m), 3.50-3.58(2H, m), 2.47-2.52(2H, m), 2.25(6H, s) 
     IR (KBr) cm -1  : 1657, 1627 
     Elemental analysis (%): C 19  H 20  N 4  O 3   
     Calcd.: C 64.76, H 5.72, N 15.90. 
     Found: C 64.41, H 5.87, N 15.50. 
     EXAMPLE 8 
     N-(3-Chlorophenyl)-4-hydroxy-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 8) 
     Compound 8 was obtained in the same manner as in Example 1 except for the use of 3-chloroaniline instead of n-butylamine (yield 75%). 
     Melting point: 295-298° C. (dimethylsulfoxide-water) 
     MS (EI) m/e: 391, 393(M + ), 265 
     NMR (CF 3  COOD) δ (ppm): 9.43(1H, dd, J=8, 2 Hz), 8.69 (1H, dd, J=6, 2 Hz), 7.95(1H, dd, J=8, 6 Hz), 7.81-7.88(3H, m), 7.64(1H, s), 7.52-7.59(2H, m), 7.31-7.43(3H, m) 
     IR (KBr) cm -1  : 1660, 1592, 1538 
     Elemental analysis (%): C 21  H 14  ClN 3  O 3   
     Calcd.: C 64.38, H 3.60, N 10.72. 
     Found: C 64.31, H 3.16, N 10.50. 
     EXAMPLE 9 
     4-Hydroxy-N-(3-methylphenyl)-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 9) 
     Compound 9 was obtained in the same manner as in Example 1 except for the use of m-toluidine instead of n-butylamine (yield 74%). 
     Melting point: 230-299° C. (dimethylsulfoxide-water) 
     MS (EI) m/e: 371(M + ), 265, 107 
     NMR (CF 3  COOD) δ (ppm): 9.43(1H, dd, J=8, 2 Hz), 8.69 (1H, dd, J=6, 2 Hz), 7.94(1H, dd, J=8, 6 Hz), 7.80-7.88(3H, m), 7.53-7.59(2H, m), 7.20-7.40 (4H, m), 2.41(3H, s) 
     IR (KBr) cm -1  : 1660, 1621, 1563 
     Elemental analysis (%): C 22  H 17  N 3  O 3   
     Calcd.: C 71.15, H 4.61, N 11.31. 
     Found: C 71.42, H 4.43, N 11 32. 
     EXAMPLE 10 
     4-Hydroxy-N-(2-methylphenyl)-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 10) 
     Compound 10 was obtained in the same manner as in Example 1 except for the use of o-toluidine instead of n-butylamine (yield 74%). 
     Melting point: 280-283° C. (dimethylsulfoxide-water) 
     MS (EI) m/e: 371(M + ), 265, 107 
     NMR (CF 3  COOD) δ (ppm): 9.44(1H, dd, J=8, 2 Hz), 8.70 (1H, dd, J=6, 2 Hz), 7.95(1H, dd, J=8, 6 Hz), 7.79-7.89(3H, m), 7.47-7.59(3H, m), 7.28-7.39(3H, m), 2.34(3H, s) 
     IR (KBr) cm -1  : 1658, 1620, 1551 
     Elemental analysis (%): C 22  H 17  N 3  O 3   
     Calcd.: C 71.15, H 4.61, N 11.30. 
     Found: C 71.31, H 4.42, N 11.25. 
     EXAMPLE 11 
     4-Hydroxy-N-(3-nitrophenyl)-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 11) 
     Compound 11 was obtained in the same manner as in Example 1 except for the use of 3-nitroaniline instead of n-butylamine (yield 77%). 
     Melting point: &gt;300° C. (dimethylsulfoxide-water) 
     MS (EI) m/e 402(M + ), 265, 263 
     NMR (CF 3  COOD) δ (ppm): 9.45(1H, dd, J=8, 2 Hz), 8.76 (1H, t, J=2 Hz), 8.71(1H, dd, J=6, 2 Hz), 8.24(1H, dd, J=8, 2 Hz), 7.91-7.99(2H, m), 7.80-7.87(3H, m), 7.69(1H, t, J=8 Hz), 7.54-7.58(2H, m) 
     IR (KBr) cm -1  : 1660, 1548 
     Elemental analysis (%): C 21  H 14  N 4  O 5   
     Calcd.: C 62.69, H 3.51, N 13.92. 
     Found: C 62.97, H 3.09, N 13.87. 
     EXAMPLE 12 
     4-Hydroxy-2-oxo-1-phenyl-N-(2-thiazolyl)-1H-1,8-naphthyridine-3-carboxamide (Compound 12) 
     Compound 12 was obtained in the same manner as in Example 1 except for the use of 2-aminothiazole instead of n-butylamine (yield 81%). 
     Melting point: &gt;300° C. (dimethylformamide-water) 
     MS (EI) m/e: 364(M + ), 265, 100 
     NMR (CF 3  COOD) δ (ppm): 9.48(1H, dd, J=8, 2 Hz), 8.78 (1H, dd, J=6, 2 Hz), 8.01(1H, dd, J=8, 6 Hz), 8.77-8.90(4H, m), 7.62(1H, d, J=4 Hz), 7.52-7.56(2H, m) 
     IR (KBr) cm -1  : 1652, 1620, 1547 
     Elemental analysis (%): C 18  H 12  N 4  O 3  S 
     Calcd.: C 59.33, H 3.32, N 15.38. 
     Found: C 59.76, H 3.00, N 15.57. 
     EXAMPLE 13 
     N-(2-Benzothiazolyl)-4-hydroxy-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 13) 
     Compound 13 was obtained in the same manner as in Example 1 except for the use of 2-aminobenzothiazole instead of n-butylamine (yield 51%). 
     Melting point: &gt;300° C. (dimethylformamide-water) 
     MS (EI) m/e: 414(M + ), 265, 150 
     NMR (CF 3  COOD) δ (ppm): 9.49(1H, dd, J=8, 2 Hz), 8.80 (1H, dd, J=6, 2 Hz), 8.12(1H, d, J=8 Hz), 8.03(1H, dd, J=8, 6 Hz), 7.75-7.97(6H, m), 7.53-7.61(2H, m) 
     IR (KBr) cm 1658, 1616, 1532 
     Elemental analysis (%): C 22  H 14  N 4  O 3  S 
     Calcd.: C 63.76, H 3.40, N 13.52. 
     Found: C 63.59, H 3.01, N 13.21. 
     EXAMPLE 14 
     N-(4-Chlorophenyl)-4-hydroxy-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 14) 
     Dimethylsulfoxide (20 ml) and 0.92 ml (0.0066 mol) of triethylamine were added to 1.5 g (0.0063 mol) of Compound IXa obtained in Reference Example 3 and 0.85 ml (0.006 mol) of 4-chlorophenyl isocyanate, and the mixture was stirred overnight. The mixture was poured into 150 ml of 4N aqueous solution of hydrochloric acid, and the precipitate was taken by filtration and then added to 150 ml of ethyl acetate. The mixture was stirred for 30 minutes and the crystals were taken by filtration. Recrystallization from dimethylsulfoxide-water gave 1.4 g (yield 56%) of Compound 14 as colorless crystals. 
     Melting point: 281-286° C. (dimethylsulfoxide-water) 
     MS (EI) m/e: 391(M + ), 265, 127 
     NMR (CF 3  COOD) δ (ppm): 9.43(1H, dd, J=8, 2 Hz), 8.69 (1H, dd, J=6, 2 Hz), 7.94(1H, dd, J=8, 4 Hz), 7.78-7.87(3H, m), 7.42-7.59(6H, m) 
     IR (KBr) cm -1  : 1660, 1593, 1548 
     Elemental analysis (%): C 21  H 14  ClN 3  O 3   
     Calcd.: C 64.38, H 3.60, N 10.72. 
     Found: C 64.19, H 3.57, N 10.52. 
     EXAMPLE 15 
     4-Hydroxy-N-(4-nitrophenyl)-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 15) 
     Compound 15 was obtained in the same manner as in Example 14 except for the use of 4-nitrophenyl isocyanate instead of 4-chlorophenyl isocyanate (yield 42%). 
     Melting point: &gt;300° C. (dimethylsulfoxide-water) 
     MS (EI) m/e: 402(M + ), 265, 77 
     NMR (CF 3  COOD) δ (ppm): 9.45(1H, dd, J=8, 2 Hz), 8.74 (1H, dd, J=6, 2 Hz), 8.39(2H, d, J=9 Hz), 7.80-8.01 (6H, m), 7.50-7.67(2H, m) 
     IR (KBr) cm -1  : 1659, 1548, 1511 
     EXAMPLE 16 
     4-Hydroxy-N-(4-methoxyphenyl)-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 16) 
     Compound 16 was obtained in the same manner as in Example 14 except for the use of 4-methoxyphenyl isocyanate instead of 4-chlorophenyl isocyanate (yield 42%). 
     Melting point: &gt;300° C. (dimethylsulfoxide-water) 
     MS (EI) m/e: 387(M + ), 265, 123 
     NMR (CF 3  COOD) δ (ppm): 9.43(1H, dd, J=8, 2 Hz), 8.69 (1H, dd, J=6, 2 Hz), 7.94(1H, dd, J=8, 6 Hz), 7.80-7.92(3H, m), 7.45-7.66(4H, m), 7.08-7.23 (2H, m) 
     IR (KBr) cm -1  : 1657, 1602, 1554 
     Elemental analysis (%): C 22  H 17  N 3  O 4   
     Calcd.: C 68.21, H 4.42, N 10.84. 
     Found: C 68.18, H 4.46, N 10.80. 
     EXAMPLE 17 
     4-Hydroxy-N-(4-methylphenyl)-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 17) 
     Compound 17 was obtained in the same manner as in Example 14 except for the use of 4-methylphenyl isocyanate instead of 4-chlorophenyl isocyanate (yield 45%). 
     Melting point: &gt;300° C. (dimethylsulfoxide-water) 
     MS (EI) m/e: 371(M + ), 265, 107 
     NMR (CF 3  COOD) δ (ppm): 9.43(1H, dd, J=8, 2 Hz), 8.68 (1H, dd, J=6, 2 Hz), 7.94(1H, dd, J=8, 6 Hz), 7.76-7.91(3H, m), 7.50-7.64(2H, m), 7.27-7.41 (4H, m), 2.40(3H, s) 
     IR (KBr) cm -1  : 1658, 1598, 1550 
     Elemental analysis (%): C 22  H 17  N 3  O 3   
     Calcd.: C 71.14, H 4.61, N 11.31. 
     Found: C 70.83, H 4.64, N 11.17. 
     EXAMPLE 18 
     4-Hydroxy-N-(3-methoxyphenyl)-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 18) 
     Compound 18 was obtained in the same manner as in Example 14 except for the use of 3-methoxyphenyl isocyanate instead of 4-chlorophenyl isocyanate (yield 48%). 
     Melting point: 275-280° C. (dimethylsulfoxide-water) 
     MS (EI) m/e: 387(M + ), 265, 123 
     NMR (CF 3  COOD) δ (ppm): 9.44(1H, dd, J=8, 2 Hz), 8.69 (1H, dd, J=6, 2 Hz), 7.94(1H, dd, J=8, 6 Hz), 7.78-7.90(4H, m), 7.32-7.62(5H, m), 4.04(3H, s) 
     IR (KBr) cm -1  : 1656, 1593, 1549 
     Elemental analysis (%): C 22  H 17  N 3  O 4   
     Calcd.: C 68.21, H 4.42, N 10.85. 
     Found: C 67.81, H 4.39, N 10.80. 
     EXAMPLE 19 
     4-Hydroxy-N-(2-methoxyphenyl)-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 19) 
     Compound 19 was obtained in the same manner as in Example 14 except for the use of 2-methoxyphenyl isocyanate instead of 4-chlorophenyl isocyanate (yield 52%). 
     Melting point: &gt;300° C. (dimethylsulfoxide-water) 
     MS (EI) m/e: 387(M + ), 265, 123 
     NMR (CF 3  COOD) δ (ppm): 9.45(1H, dd, J=8, 2 Hz), 8.67 (1H, dd, J=6, 2 Hz), 7.78-8.09(5H, m), 7.50-7.69 (2H, m), 7.34(1H, t, J=8 Hz), 7.04-7.20(2H, m), 3.94(3H, s) 
     IR (KBr) cm -1  : 1600, 1577, 1548 
     Elemental analysis (%): C 22  H 17  N 3  O 4 .0.1H 2  O 
     Calcd.: C 67.89, H 4.45, N 10.80. 
     Found: C 67.78, H 4.43, N 10.64. 
     EXAMPLE 20 
     4-Hydroxy-2-oxo-l,N-diphenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 20) 
     Compound 20 was obtained in the same manner as in Example 14 except for the use of phenyl isocyanate instead of 4-chlorophenyl isocyanate (yield 50%). 
     Melting point: &gt;300° C. (dimethylsulfoxide-water) 
     MS (EI) m/e: 357(M + ), 265, 197 
     NMR (CF 3  COOD) δ (ppm): 9.44(1H, dd, J=8, 2 Hz), 8.69 (1H, dd, J=6, 2 Hz), 7.78-8.02(4H, m), 7.32-7.68 (7H, m) 
     IR (KBr) cm -1  : 1663, 1598, 1548 
     Elemental analysis (%): C 21  H 15  N 3  O 3   
     Calcd.: C 70.58, H 4.23, N 11.75. 
     Found: C 70.31, H 4.13, N 11.46. 
     EXAMPLE 21 
     N-(1-Benzylpiperidin-4-yl)-4-hydroxy-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 21) 
     Compound 21 was obtained in the same manner as in Example 1 except for the use of 4-amino-1-benzylpiperidine instead of n-butylamine (yield 97%). 
     Melting point: 205-206° C. (ethanol-methanol) 
     MS (EI) m/e: 454(M + ), 265, 91, 82 
     NMR (CF 3  COOD) δ (ppm): 9.41(1H, dd, J=8, 2 Hz), 8.65 (1H, dd, J=6, 2 Hz), 7.94(1H, t, J=7 Hz), 7.77-7.90 (3H, m), 7.42-7.64(7H, m), 4.42(2H, s), 3.86(2H, d, J=12 Hz), 3.42-3.73(1H, m), 3.30(2H, t, J=12 Hz), 2.47(2H, d, J=12 Hz), 2.07-2.25(2H, m) 
     Elemental analysis (%): C 27  H 20  N 4  O 3   
     Calcd.: C 71.35, H 5.77, N 12.33. 
     Found: C 71.38, H 5.95, N 12.52. 
     EXAMPLE 22 
     4-Hydroxy-2-oxo-1-phenyl-N-(thiazolin-2-yl)-1H-1,8-naphthyridine-3-carboxamide (Compound 22) 
     Compound 22 was obtained in the same manner as in Example 1 except for the use of 2-aminothiazoline instead of n-butylamine (yield 71%). 
     Melting point: &gt;300° C. (xylene) 
     MS (EI) m/e: 366(M + ), 347 
     IR (KBr) cm -1  : 1701, 1593, 1549 
     NMR (CF 3  COOD) δ (ppm): 9.79(1H, dd, J=8, 2 Hz), 8.64 (1H, dd, J=6, 2 Hz), 7.93(1H, t, J=7 Hz), 7.75-7.87 (3H, m), 7.45-7.58(2H, m), 4.85(2H, t, J=8 Hz), 3.78(2H, t, J=8 Hz) 
     Elemental analysis (%): C 18  H 14  N 4  O 3  S.0.2H 2  O 
     Calcd.: C 58.43, H 3.92, N 15.14. 
     Found: C 58.36, H 3.64, N 14.87. 
     EXAMPLE 23 
     4-Hydroxy-2-oxo-1-phenyl-N-(pyrazin-2-yl)-1H-1,8-naphthyridine-3-carboxamide (Compound 23) 
     Compound 23 was obtained in the same manner as in Example 1 except for the use of 2-aminopyrazine instead of n-butylamine (yield 38%). 
     Melting point: &gt;300° C. (xylene) 
     MS (EI) m/e: 359(M + ), 263 
     IR (KBr) cm -1  : 1659, 1621, 1520 
     NMR (CF 3  COOD) δ (ppm): 9.92(1H, s), 9.48(1H, dd, J=8, 2 Hz), 9.25(1H, dd, J=3, 1 Hz), 8.72-8.74(2H, m), 8.74(1H, t, J=7 Hz), 7.78-7.88(3H, m), 7.50-7.60 (2H, m) 
     Elemental analysis (%): C 19  H 13  N 5  O 3   
     Calcd.: C 63.51, H 3.65, N 19.49. 
     Found: C 63.68, H 3.39, N 19.19. 
     EXAMPLE 24 
     4-Hydroxy-2-oxo-1-phenyl-N-(5-ethyl-1,3,4-thiadiazol-2-yl)-1H-1,8-naphthyridine-3-carboxamide (Compound 24) 
     Compound 24 was obtained in the same manner as in Example 1 except for the use of 2-amino-5-ethyl-1,3,4-thiadiazole instead of n-butylamine (yield 68%). 
     Melting point: &gt;298° C. (DMF-water) 
     MS (EI) m/e: 393(M + ), 265, 263 
     IR (KBr) cm -1  : 1660, 1530, 1471 
     NMR (CF 3  COOD) δ (ppm): 9.46(1H, dd, J=8, 2 Hz), 8.77 (1H, dd, J=6, 2 Hz), 8.10(1H, t, J=7 Hz), 7.78-7.92 (3H, m), 7.50-7.58(2H, m), 3.46(2H, q, J=7 Hz), 1.67(3H, t, J=7 Hz) 
     Elemental analysis (%): C 19  H 15  N 5  O 3  S 
     Calcd.: C 58.00, H 3.84, N 17.80. 
     Found: C 58.16, H 3.59, N 17.58. 
     EXAMPLE 25 
     4-Hydroxy-N-(2-methoxypyridin-5-yl)-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 25) 
     Compound 25 was obtained in the same manner as in Example 1 except for the use of 5-amino-2-methoxypyridine instead of n-butylamine (yield 71%). 
     Melting point: 285-287° C. (DMF-water) 
     MS (EI) m/e: 388(M + ), 265, 124 
     IR (KBr) cm -1  : 1661, 1544, 1493 
     NMR (CF 3  COOD) δ (ppm): 9.44(1H, d, J=4 Hz), 9.23(1H, brs), 8.71-8.80(2H, m), 7.80-8.01(4H, m), 7.51-7.60(3H, m), 4.34(3H, s) 
     Elemental analysis (%): C 21  H 16  N 4  O 4 .0.4H 2  O 
     Calcd.: C 63.76, H 4.28, N 14.17. 
     Found: C 63.71, H 3.99, N 14.07. 
     EXAMPLE 26 
     N-(2-Chloropyridin-5-yl)-4-hydroxy-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 26) 
     Compound 26 was obtained in the same manner as in Example 1 except for the use of 5-amino-2-chloropyridine instead of n-butylamine (yield 64%). 
     Melting point: 282-283° C. (chloroform) 
     MS (EI) m/e: 392(M + ), 265, 128 
     IR (KBr) cm -1  : 1662, 1542, 1460 
     NMR (CF 3  COOD) δ (ppm): 9.69(1H, brs), 9.46(1H, dd, J=8, 2 Hz), 8.88(1H, dd, J=6, 2 Hz), 8.72(1H, d, J=6 Hz), 8.07(1H, d, J=10 Hz), 7.97(1H, t, J=7 Hz), 7.82-7.86(3H, m), 7.52-7.57(2H, m) 
     Elemental analysis (%): C 20  H 13  N 4  O 3  Cl 
     Calcd.: C 61.16, H 3.34, N 14.26. 
     Found: C 60.98, H 3.32, N 14.15. 
     EXAMPLE 27 
     4-Hydroxy-N-morpholino-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 27) 
     Compound 27 was obtained in the same manner as in Example 1 except for the use of N-aminomorpholine instead of n-butylamine (yield 87%). 
     Melting point: 263-266° C. (xylene) 
     MS (EI) m/e: 366(M + ), 263, 102 
     IR (KBr) cm -1  : 1618, 1473, 1440, 1113 
     NMR (CF 3  COOD) δ (ppm): 9.42(1H, dd, J=8, 2 Hz), 8.76 (1H, dd, J=6, 2 Hz), 7.98(1H, t, J=7 Hz), 7.80-7.86 (3H, m), 7.48-7.53(2H, m) 
     Elemental analysis (%): C 19  H 18  N 4  O 4   
     Calcd.: C 62.29, H 4.59, N 15.29. 
     Found: C 62.46, H 4.80, N 15.40. 
     EXAMPLE 28 
     4-Hydroxy-2-oxo-1-phenyl-N-(4-pyridylmethyl)-1H-1,8-naphthyridine-3-carboxamide (Compound 28) 
     Compound 28 was obtained in the same manner as in Example 1 except for the use of 4-aminomethylpyridine instead of n-butylamine (yield 73%). 
     Melting point: 232-234° C. (xylene) 
     MS (EI) m/e: 372(M + ), 263, 238, 108 
     IR (KBr) cm -1  : 1660, 1626, 1535 
     NMR (CF 3  COOD) δ (ppm): 9.42(1H, dd, J=8, 2 Hz), 8.81 (1H, d, J=6 Hz), 8.69(1H, dd, J=6, 2 Hz), 8.17(1H, d, J=6 Hz), 7.96(1H, t, J=7 Hz), 7.78-7.85(3H, m), 7.48-7.55(2H, m), 5.10(2H, s) 
     Elemental analysis (%): C 21  H 16  N 4  O 3   
     Calcd.: C 67.73, H 4.33, N 15.03. 
     Found C 67.74, H 4.27, N 14.89. 
     EXAMPLE 29 
     4-Hydroxy-2-oxo-1-phenyl-N-(3-pyridylmethyl)-1H-1,8-naphthyridine-3-carboxamide (Compound 29) 
     Compound 29 was obtained in the same manner as in Example 1 except for the use of 3-aminomethylpyridine instead of n-butylamine (yield 65%). 
     Melting point: 222-224° C. (xylene) 
     MS (EI) m/e: 372(M + ), 263, 238, 108 
     IR (KBr) cm -1  : 1658, 1556 
     NMR (CF 3  COOD) δ (ppm): 9.40(1H, dd, J=8, 2 Hz), 9.02 (1H, s), 8.76-8.83(2H, m), 8.64(1H, dd, J=6, 2 Hz), 8.14(1H, t, J=7 Hz), 7.92(1H, t, J=7 Hz), 7.78-7.86(3H, m), 7.47-7.55(2H, m), 5.02(2H, s) 
     Elemental analysis (%): C 21  H 16  N 4  O 3   
     Calcd.: C 67.73, H 4.33, N 15.05. 
     Found: C 67.59, H 4.06, N 14.84. 
     EXAMPLE 30 
     N-(4-Aminophenyl)-4-hydroxy-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 30) 
     Compound 30 was obtained in the same manner as in Example 1 except for the use of phenylenediamine instead of n-butylamine (yield 90%). 
     Melting point: &gt;300° C. (xylene) 
     MS (EI) m/e: 372(M + ), 108 
     IR (KBr) cm -1  : 1658, 1627, 1563, 1553, 1515 
     NMR (CF 3  COOD) δ (ppm): 9.44(1H, dd, J=8, 2 Hz), 8.69 (1H, dd, J=6, 2 Hz), 7.73-7.96(6H, m), 7.53-7.65 (4H, m) 
     Elemental analysis (%): C 21  H 16  N 4  O 3   
     Calcd.: C 67.73, H 4.33, N 15.04. 
     Found C 67.77, H 4.23, N 14.76. 
     EXAMPLE 31 
     4-Hydroxy-N-(3-methylpyridin-4-yl)-2-oxo-1-phenyl-1H-1,8-naphthyridine-3-carboxamide (Compound 31) 
     Compound 31 was obtained in the same manner as in Example 1 except for the use of 4-amino-3-methylpyridine instead of n-butylamine (yield 62%). 
     Melting point: 276-279° C. (DMF) 
     MS (EI) m/e: 372, 265, 263, 108 
     IR (KBr) cm -1  : 1666, 1594, 1434, 1394 
     Elemental analysis (%): C 21  H 16  N 4  O 3 .0.4H 2  O 
     Calcd.: C 66.45, H 4.46, N 14.76. 
     Found: C 66.43, H 4.32, N 14.79. 
     EXAMPLE 32 
     4-Hydroxy-2-oxo-1-phenyl-N-(2-pyridyl)-1H-1,8-naphthyridine-3-carboxamide (Compound 32) 
     In 40 ml of N,N-dimethylacetamide was dissolved 1.9 g (0.0092 mol) of 2-ethoxycarbonyl-N-(2-pyridyl)acetamide, and 1.0 g (0.025 mol) of 60% sodium hydride was added to the solution under cooling. After evolution of hydrogen ceased, 2.0 g (0.0083 mol) of Compound Va obtained in Reference Example 1 was added in small portions to the mixture, followed by heating at 110° C. for one hour. The mixture was cooled and the solvent was evaporated under reduced pressure. Then, 50 ml of ethyl acetate and 50 ml of water were added to the residue, and the formed crystals were taken by filtration and dried. Recrystallization from N,N-dimethylformamide gave 0.88 g (yield 30%) of Compound 32 as light yellow crystals. 
     Melting point: &gt;300° C. (DMF) 
     MS (EI) m/e: 358(M + ), 263, 94 
     NMR (CF 3  COOD) δ (ppm): 9.46(1H, dd, J=8, 2 Hz), 8.77 (1H, d, J=6 Hz), 8.55-8.65(2H, m), 7.98-8.06(2H, m), 7.81-7.92(4H, m), 7.52-7.58(2H, m) 
     IR (KBr) cm -1  : 1652, 1520, 1491, 1436 
     Elemental analysis (%): C 20  H 14  N 4  O 3   
     Calcd.: C 67.03, H 3.94, N 15.63. 
     Found: C 67.07, H 3.85, N 15.34. 
     EXAMPLE 33 
     Tablets 
     Tablets, each having the following composition, are prepared in a conventional manner. 
     
         ______________________________________Compound 1        50 mgLactose           60 mgPotato starch     30 mgPolyvinyl alcohol  2 mgMagnesium stearate              1 mgTar pigment       trace______________________________________ 
    
     EXAMPLE 34 
     Powder 
     Powder having the following composition is prepared in a conventional manner. 
     
         ______________________________________  Compound 2            50 mg  Lactose  300 mg______________________________________ 
    
     EXAMPLE 35 
     Syrup 
     Syrup having the following composition is prepared in a conventional manner. 
     
         ______________________________________Compound 1              50    mgRefined white sugar     30    gEthyl p-hydroxybenzoate 40    mgPropyl p-hydroxybenzoate                   10    mgStrawberry flavor       0.1   cc______________________________________ 
    
     Water is added to the composition to make the whole volume 100 cc. 
     EXAMPLE 36 
     Syrup 
     Syrup having the following composition is prepared in a conventional manner. 
     
         ______________________________________Compound 2              50    mgRefined white sugar     30    gEthyl p-hydroxybenzoate 40    mgPropyl p-hydroxybenzoate                   10    mgStrawberry flavor       0.1   cc______________________________________ 
    
     Water is added to the composition to make the whole volume 100 cc. 
     REFERENCE EXAMPLE 1 
     1-Phenyl-2H-pyrido[2,3-d][1,3]oxazine-2,4(1H)-dione (Compound Va) 
     In a mixture of 70 ml of 1,2-dichloroethane and 7 ml of dioxane was dissolved 7.0 g (0.031 mol) of methyl 2-anilinonicotinate [J. Org. Chem., 39, 1803 (1974)]. After 11 ml (0.092 mol) of trichloromethyl chloroformate was added dropwise to the solution at 60° C. with stirring, the mixture was refluxed for 3 hours. The mixture was slightly cooled and 0.25 g of activated carbon was added thereto, followed by refluxing for further 30 minutes in a nitrogen flow. The mixture was cooled to room temperature, filtered and concentrated. Recrystallization from methylene chloride-isopropyl ether gave 6.5 g (yield 87%) of Compound Va as colorless crystals. 
     Melting point: 196-198° C. 
     Elemental analysis (%): C 13  H 8  N 2  O 3   
     Calcd.: C 65.00, H 3.36, N 11.66. 
     Found: C 65.11, H 3.22, N 11.48. 
     IR (KBr) νmax (cm -1 ): 1791, 1727, 1584 
     NMR (CDCl 3 ) δ (ppm): 8.58(1H, dd, J=5, 2 Hz), 8.48(1H, dd, J=8, 2 Hz), 7.51-7.63(3H, m), 7.33-7.37(2H, m), 7.29(1H, dd, J=8, 5 Hz) 
     MS (m/z): 240(M + ), 196, 168 
     REFERENCE EXAMPLE 2 
     3-Ethoxycarbonyl-4-hydroxy-1-phenyl-1,8-naphthyridin-2(1H)-one (Compound IIa) 
     To 25 ml of N,N-dimethylacetamide was added 25 ml (0.16 mol) of diethyl malonate, and 0.80 g (0.020 mol) of 60% sodium hydride was added to the mixture under ice cooling. After evolution of hydrogen ceased, 4.0 g (0.017 mol) of Compound Va obtained in Reference Example 1 was added to the reaction mixture. The temperature was gradually elevated and the mixture was heated at 150° C. for 2.5 hours. The mixture was then cooled and 100 ml of ethyl acetate was added. The precipitate was taken by filtration and dissolved in 100 ml of water. The solution was made acidic with conc. hydrochloric acid and the precipitated crystals were taken by filtration. The crystals were washed with water and dried under reduced pressure. Recrystallization from isopropyl alcohol-ethanol gave 4.3 g (yield 88%) of Compound IIa as colorless crystals. 
     Melting point: 247-252° C. 
     Elemental analysis (%): C 17  H 14  N 2  O 4   
     Calcd.: C 65.80, H 4.55, N 9.03. 
     Found: C 66.05, H 4.35, N 8.98. 
     IR (KBr) νmax (cm -1 ): 1670, 1615, 466 
     NMR (CF 3  COOD) δ (ppm): 8.48(1H, dd, J=4, 2 Hz), 8.46 (1H, dd, J=8, 2 Hz), 7.38-7.56(3H, m), 7.32(1H, dd, J=8, 4 Hz), 7.21-7.26(2H, m), 4.32(2H, q, J=7 Hz), 1.28(3H, t, J=7 Hz) 
     MS (m/z): 310(M + ), 263, 77 
     REFERENCE EXAMPLE 3 
     4-Hydroxy-1-phenyl-1,8-naphthyridin-2(1H)-one (Compound IXa) 
     To 70 ml of 2N sodium hydroxide solution was added 2 g (0.068 mol) of Compound IIa obtained in Reference Example 2, and the mixture was heated to reflux for one hour. After cooling, 2N hydrochloric acid was added to neutralize the mixture. The precipitated crystals was taken by filtration and dried. Recrystallization from dimethylsulfoxide-water gave 1.4 g (yield 86%) of Compound IXa. 
     Melting poing: 300° C. 
     Elemental analysis (%): C 14  H 10  N 2  O 2 .0.2H 2  O 
     Calcd.: C 69.52, H 4.33, N 11.58. 
     Found: C 69.28, H 3.99, N 11.53. 
     IR (KBr) νmax (cm -1 ): 1680, 1641, 1615 
     NMR (CF 3  COOD) δ (ppm): 11.79(1H, brs) 8.40(1H, dd, 
     J=4, 2 Hz), 8.26(1H, dd, J=8, 2 Hz), 7.37-7.53(3H, m), 7.18-7.28(3H, m), 5.95(1H, s) 
     MS (m/z): 238(M + ), 237, 195, 77