QUINAZOLINE DERIVATIVES AND ANTIHYPERTENSIVE PREPARATIONS CONTAINING SAME AS EFFECTIVE COMPONENTS

Abstract: Disclosed herein is an antihypertensive preparation containing, as an active component, a novel quinazoline derivative represented by the following general formula or a salt thereof: wherein R¹⁰⁰ means a hydrogen atom or methoxy group, R²⁰⁰ and R³⁰⁰ denote individually a hydrogen atom or lower alkoxy group, R⁴⁰⁰ is a hydrogen atom or amino group, ℓ stands for 2 or 3, and Het is a specific hetero ring group.

Description: This invention relates to novel quinazoline derivatives useful for the treatment of hypertension. Numerous quinazoline derivatives have been known to date, including especially piperazinoquinazolines such as various acid amide compounds, eg. prazosin (Japanese Patent Publication No. 22135/1970; US Patent No. 3,511,836), terazosin (Japanese Patent Laid-Open No. 27588/1979; US Patent Nos. 4,026,894 and 4,112,097) and those disclosed in Japanese Patent Laid-Open No. 116052/1982 as well as piperazinoquinazolines of the pyrimidine structure such as those disclosed in Japanese Patent Laid-Open No. 181068/1982. Reference may also be made to EP-A-0 039 190 and EP-A-0 055 583. EP-A-0 039 190 discloses a series of piperazinyl quinazoline compounds in which the piperazine ring is substituted with a thiazole or cycloheptatrienone ring or a bicyclic ring system containing a 5-membered heterocyclic ring fused to a pyridine, benzene, cycloheptatriene or cycloheptane ring. EP-A-0 055 583 discloses a series of piperazinyl quinazoline compounds in which the piperazinyl ring is substituted with a diazinyl or triazinyl group. These conventional quinazoline derivatives have been subjected to further investigation, whereby some of the quinazoline derivatives have already been clinically applied as antihypertensive agents. They are classified as α-adrenergic antihypertensive agents. Although they have excellent clinical effects, some drawbacks have been observed that they lack long-acting properties and develop orthostatic hypotension as an undesirable side effect. An object of this invention is to provide novel quinazoline derivatives and their salts. Another object of this invention is to provide antihypertensive preparations which contain these compounds as active components. A further object of this invention is to provide a process for the preparation of these compounds. The present inventors have found through zoopery that compounds represented by the below-described general formula [I] have extremely strong and long-acting antihypertensive effects and can reduce or substantially avoid the development of the above-mentioned orthostatic hypotension compared with the conventional compounds, leading to completion of this invention. This invention provides, a quinazoline derivative represented by the following general formula [I] or a pharmacologically acceptable salt thereof: wherein R¹⁰⁰ means a hydrogen atom or methoxy group, R²⁰⁰ and R³⁰⁰ denote individually a hydrogen atom or lower alkoxy group, R⁴⁰⁰ is a hydrogen atom or amino group, ℓ stands for 2 or 3, and Het is represented by any one of the following formulae [II] through [XIX]: wherein, in the formula [II], either single or double bond is formed between the 3- and 4-positions, R² means a hydrogen atom or a lower alkyl, aralkyl, cyano or formyl group, R³ denotes a hydrogen atom or a lower alkoxycarbonyl or phenyl group, R⁴ is a hydrogen atom or a lower alkyl, lower cycloalkyl, hydroxy-substituted lower alkyl, lower alkoxy-substituted lower alkyl, phenyl or aralkyl group, and X stands for an oxygen or sulfur atom, in the formula [III], either single or double bond is formed between the 2- and 3-positions, and R⁵ means a hydrogen atom or a lower alkyl group, in the formula [IV], R⁶ and R⁷ mean individually a hydrogen atom or a lower alkyl group, in the formula [V], R⁸ and R⁹ mean individually a hydrogen atom or a lower alkyl group, in the formula [VI], m stands for 2 or 3, and R¹⁰ means a hydrogen atom or a lower alkyl group, in the formula [VII], n stands for an integer of from 2 to 4, in the formula [VIII], R¹¹ to R¹³ mean individually a hydrogen atom or a lower alkyl group, in the formula [IX], R¹⁴ means a hydrogen atom or a hydroxyl, lower alkyl, -NR³¹R³² in which R³¹ is a hydrogen atom or a lower alkyl group and R³² is a hydrogen atom or a lower alkyl or lower acyl group, lower alkylthio or lower alkoxy group, R¹⁵ denotes a lower acyl, lower alkoxycarbonyl, -CONR³³R³⁴ in which R³³ is a hydrogen atom or a lower alkyl group, R³⁴ is a hydrogen atom or a lower alkyl, phenyl, aralkyl, halogen-substituted lower alkyl or cycloalkyl group or R³³ and R³⁴ couples together to form a methylene moiety which in turn forms a ring having 4 to 5 carbon atoms together with the associated nitrogen atom, -CONHNR³⁵R³⁶ in which R³⁵ and R³⁶ are individually a lower alkyl group, -CH₂CONHR³⁷ in which R³⁷ is a lower alkyl, or cyano-group, in the formula [X], R¹⁶ means a lower alkyl group, in the formula [XI], R¹⁷ and R¹⁸ mean individually a hydrogen atom or a lower alkyl group, in the formula [XII], R¹⁹ through R²¹ means a hydrogen atom or a lower alkoxy group, and R²² denotes -NR³⁸R³⁹ in which R³⁸ and R³⁹ are individually a hydrogen atom or a lower alkyl group, or a hydrogen atom, in the formula [XIII], R²³ means a hydrogen atom or a lower alkyl group, and R²⁴ denotes a hydrogen atom or a lower alkylthio group, in the formula [XIV], R²⁵ means an alkyl, cycloalkyl, hydroxy-substituted lower alkyl group, lower alkoxy-substituted lower alkyl, di(lower alkylamino)-substituted lower alkyl or aralkyl group, in the formula [XV], R²⁶ means a lower alkyl group, in the formula [XVI], R²⁷ and R²⁸ are either same or different and mean individually a lower alkoxy, hydroxyl or lower alkylamino group, or R²⁷ and R²⁸ couples together to form a lower alkyl-substituted imino group, and in the formula [XVIII], R²⁹ and R³⁰ are either same or different and mean individually a lower alkyl group; and as an invention on utility, an antihypertensive preparation containing the quinazoline derivative or its pharmacologically acceptable salt as an active component. Definitions The term "lower alkyl" as used herein means C₁₋₄ alkyl, and references to "lower alkylthio" and "lower alkylamino" shall be construed accordingly. Similarly, the terms "lower alkoxy" and "lower alkoxy carbonyl" refer to compounds containing a C₁₋₄ alkoxy moiety. The term "lower cycloalkyl" means C₃-₅ cycloalkyl and the term "cycloalkyl" means C₄-₇ cycloalkyl. References to "aralkyl" mean a benzyl, diphenylmethyl, triphenylmethyl or 2-phenylethyl group. Particularly preferred compounds include those having the general formula [I] in which R²⁰⁰ and R³⁰⁰ are individually a methoxy group, R⁴⁰⁰ denotes an amino group and Het is represented by any one of the formulae [II] through [XIII]; those having the general formula [I] in which R¹⁰⁰ denotes a hydrogen atom, R²⁰⁰ and R³⁰⁰ denote individually a methoxy group, R⁴⁰⁰ is an amino group, ℓ stands for 2 and Het is represented by any one of the formulae [XIV] through [XIX]; and those having the general formula [I] in which R¹⁰⁰ and R⁴⁰⁰ mean individually a hydrogen atom, ℓ stands for 2 and Het is represented by the formula [II] wherein a double bond is formed between the 3- and 4-positions, R² and R³ mean individually a hydrogen atom, X denotes an oxygen atom and R⁴ is a lower alkyl group. Detailed Description of the Preferred Embodiments : [Materials of the Invention] Although materials of the present invention are the compounds represented by the general formula [I], the compounds represented by the following formula [I'] will next be mentioned as one of preferred embodiments of this invention: wherein R¹⁰⁰ means a hydrogen atom or methoxy group, the former being preferred, and ℓ stands for 2 or 3 with 2 being preferred. In the above formula [I'], Het is represented by any one of the formulae [II] to [XIII]. In the formula [II], as the lower alkyl group represented by R², may be mentioned by way of example methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group with methyl group being preferred. As an exemplary aralkyl group, may be mentioned benzyl group or diphenyl methyl group with benzyl group being preferred. R³ is a hydrogen atom or a lower alkoxycarbonyl or phenyl group with a hydrogen atom being preferred. Illustrative of the lower alkoxycarbonyl group may be methoxycarbonyl group, ethoxycarbonyl group or propoxycarbonyl group. Among these groups, ethoxycarbonyl group is preferred. As the lower alkyl group represented by R⁴, the lower alkyl group represented above by R² may be mentioned. The lower cycloalkyl group contains 3 - 5 carbon atoms with a cyclopropyl group being preferred. As an exemplary hydroxy-substituted lower alkyl group, may be mentioned a methylol group or ethylol group with an ethylol group being preferred. Illustrative of the lower alkoxy-substituted lower alkyl group may be a methoxymethyl group, ethoxymethyl group, methoxyethyl group or ethoxyethyl group. Of these, a methoxyethyl group is preferred. As the aralkyl group, may be mentioned that represented above by R². In the formula [III], as the lower alkyl group represented by R⁵, may be mentioned the lower alkyl group represented above by R² with an ethyl group being preferred. In the formula [IV], as the lower alkyl group represented by each of R⁶ and R⁷, may be mentioned the lower alkyl group represented above by R². A hydrogen atom is preferred as R⁶. As the lower alkyl groups represented respectively by R⁸ through R¹⁴ in the formulae [V], [VI], [VIII] and [IX], may be mentioned those represented above by R². In the formula [V], a lower alkyl group is preferred as R⁸ while a hydrogen atom is preferred as R⁹. In the formula [VI], m is preferably 3 and R¹⁰ denotes preferably a lower alkyl group. In the formula [VII], n stands preferably for 3. In the formula [VIII], R¹¹ and R¹² mean individually and preferably a hydrogen atom and R¹³ is preferably a lower alkyl group. In -NR³¹R³² as R¹⁴ in the formula [IX], as exemplary lower alkyl groups represented respectively by R³¹,R³², may be mentioned those represented above by R². Illustrative of the lower acyl group represented by R³² may be an acetyl group, propionyl group or butyryl group. Of these, an acetyl group is preferred. As exemplary lower alkylthio groups represented by R¹⁴, may be mentioned a methylthio group or ethylthio group with the former group being preferred. As the lower alkoxy group, may for example be mentioned a methoxy group, ethoxy group, propoxy group, isopropoxy group or butoxy group with a methoxy group being preferred. As the lower acyl group represented by R¹⁵, may be mentioned that represented above by R³² with an acetyl group being preferred. Illustrative of the lower alkoxycarbonyl group may be a methoxycarbonyl group, ethoxycarbonyl group, propoxycarbonyl group, isopropoxycarbonyl group or butoxycarbonyl group. As the lower alkyl groups represented respectively by R³³ and R³⁴, may be mentioned those represented above by R². R³³ and R³⁴may be either same or different. Illustrative of the aralkyl represented by R³⁴ may be those represented above by R². A benzyl group is preferred as the aralkyl group. As exemplary halogen-substituted lower alkyl groups, may be mentioned a trifluoromethyl group, 2-fluoroethyl group, 2,2,2-trifluoroethyl group, 2,2,3,3,3-pentafluoropropyl group or 2-chloroethyl group. Of these, a 2,2,2-trifluoroethyl group is preferred. As the cycloalkyl group, may for example be mentioned a cyclobutyl group, cyclopentyl group, cyclohexyl group or cycloheptyl group with a cyclohexyl group being preferred. As the lower alkyl groups represented respectively by R³⁵ to R³⁷ in -CONHNR³⁵R³⁶ and -CH₂CONHR³⁷, may be mentioned those represented above by R². In the formulae [X] through [XIII], illustrative of the lower alkyl groups represented respectively by R¹⁶ to R²¹, R²³, R³⁸ and R³⁹ may be those represented above by R². As the alkylthio group represented by R²⁴, may be mentioned that represented above by R¹⁴. In the formula [XI], each of R¹⁷ and R¹⁸ is preferably a lower alkyl group. As R²³ in the formula [XIII], a lower alkyl group is preferred. As R²⁴, a lower alkylthio group is preferred. Furthermore, the compounds represented by the following formula [I''] may also be mentioned as another preferred embodiment of this invention. In the above formula [I''], Het is represented by the formulae [XIV] through [XIX]. In the formula [XIV], the alkyl group represented by R²⁵ contains 5 or more carbon atoms. As such alkyl groups, may for example be mentioned amyl groups such as n-amyl group, hexyl groups such as n-hexyl groups, heptyl groups such as n-heptyl group, octyl groups such as n-octyl groups. Among these alkyl groups, n-heptyl group is particularly preferred. The cycloalkyl groups represented by R²⁵, are those containing 4 to 7 carbon atoms with cyclohexyl group containing 6 carbon atoms being particularly preferred. As illustrative hydroxy-substituted lower alkyl groups represented by R²⁵, may be mentioned methylol group and ethylol groups. Of these, the latter group is preferred. As exemplary lower alkoxy-substituted lower alkyl groups represented by R²⁵, may be mentioned those containing 2 - 8 carbon atoms, for example, methoxymethyl group, ethoxy-methyl group, methoxyethyl group or ethoxyethyl group. Of these, methoxyethyl group is preferred. As the lower(alkyl)amino-substituted lower alkyl group represented by R²⁵, may for example be mentioned 2-dimethylaminoethyl group or 2-diethylaminoethyl group. Of these, the former is preferred. As illustrative aralkyl groups represented by R²⁵, may be mentioned benzyl group, diphenylmethyl group, triphenyl methyl group or 2-phenylethyl group. Of these, benzyl group and 2-phenylethyl group are preferred. In the formula [XV], the lower alkyl group represented by R²⁶ may be a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group or tert-butyl group with methyl group being preferred. In the formula [XVI], as exemplary lower alkoxy groups represented by R²⁷ or R²⁸, may be mentioned a methoxy group, ethoxy group, propoxy group, isopropoxy group, and butoxy group. Among these groups, ethoxy groups are especially preferred. In addition, illustrative of the lower(alkyl)amino group represented by R²⁷ or R²⁸ may be methylamino group, ethylamino group, n-propylamino group, isopropylamino group, n-butylamino group, isobutylamino group, sec-butylamino group, and the tert-butylamino group. Among these groups, ethylamino group is particularly preferred. As the lower alkyl group in the lower(alkyl)-substituted imino group represented by R²⁷ or R²⁸, any one of the lower alkyl groups referred to above by way of example for R²⁶ may be mentioned with ethyl group being preferred. In the formula [XVIII], the lower alkyl groups mentioned above for R²⁶ may be mentioned as exemplary lower alkyl groups represented by R²⁹ and R³⁰. As a further preferred embodiment of this invention, may be mentioned the compounds represented by the following formula [I''']: In the above formula [I'''], R²⁰⁰ and R³⁰⁰ individually means a hydrogen atom or lower alkoxy group and R⁴ denotes a lower alkyl group. As exemplary lower alkoxy groups represented by R²⁰⁰ or R³⁰⁰, may be mentioned methoxy group, ethoxy group, propoxy group, isopropoxy group or butoxy group with methoxy group being preferred. Where R²⁰⁰ stands for a hydrogen atom, it is preferred that R³⁰⁰ stands also for a hydrogen atom. Similarly, where R²⁰⁰ stands for a lower alkoxy group, it is preferred that R³⁰⁰ is also a lower alkoxy group. In the latter case, R²⁰⁰ and R³⁰⁰ may be different from each other. Furthermore, as exemplary lower alkyl groups represented by R⁴, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group and tert-butyl group may be mentioned by way of example. Among these groups, ethyl group is preferred. Certain specific exemplary compounds of this invention will be described in Examples, which will be given later in this specification. As pharmacologically acceptable salts of the compound [I] of this invention, may be mentioned, by way of example, those obtained in combination with acids capable of forming pharmacologically-acceptable nontoxic acid addition salts which may optionally contain anions, such as its hydrochloride, hydrobromide, sulfate, bisulfate, phosphate, acid phosphate, acetate, maleate, fumarate, succinate, lactate, tartrate, benzoate, citrate, gluconate, saccharate, methanesulfonate and p-toluenesulfonate. Hydrates of such salts are also embraced in the compounds of this invention. [Preparation process] The compounds of this invention may be prepared in a process known per se in the art, for example, in accordance with the process described in Japanese Patent Laid-Open No. 181068/1982. Namely, an exemplary preparation process may be indicated by the following equation. wherein Q means a readily-removable group such as a halogen atom, C₁₋₄ alkoxy group or C₁₋₄ alkylthio group with Cℓ being preferred. The compound (1) employed in the above reaction is a known material, while as the compound (2), any one of compounds synthesized respectively in the below-given Referential Examples may be used. Compounds which will not be found in the Referential Examples but fall within the definition for the compound (2) may also be synthesized following the Referential Examples and may also be used. The reaction may be carried out by reacting the compounds (1) and (2), for example, in a suitable solvent such as isoamyl alcohol or n-butanol, under reflux, for example, at 100 to 150°C and for about 1 to 6 hours. The temperature and time and type of the solvent may be changed suitably in accordance with the types of the compounds (1) and (2). In the above reaction, the compound [I] can usually be obtained as a free base by adding a tertiary amine such as triethylamine or the like to the reaction system. Alternatively, the above reaction can directly provide the hydrochloride of the compound [I] unless such a tertiary amine is employed. The compound [I] may also be synthetically prepared by the following reaction: wherein Q is as defined above. The thus-prepared compound [I] may be isolated and purified by a usual method. Furthermore, its acid addition salts led by its hydrochloride may also be obtained by a usual method, for example, by reacting the compound [I] with an acid in an inert organic solvent, isolating the resulting precipitate, and if necessary purifying same. [Invention on Drug] As already described above, the compound [I] of this invention has a strong antihypertensive effect. It is also expected to show some effects for the improvement of heart failure. The compound of the formula [I] is generally used in the form of pharmaceutical preparations and administered through various routes such as oral, subcutaneous, intramuscular, intravenous, endonasal, skin-penetrative and rectal routes. The present invention includes pharmaceutical preparations each of which is typically composed of a pharmaceutically-acceptable carrier and as an active component, the compound of the general formula [I] or its acid addition salt. When producing preparations of this invention, they may be formed into tablets, capsules, powders, granules, troches, sansi (synchyses), cachets, elixirs, emulsions, solutions, syrups, suspensions, aerosols, ointments, formed poulitices, tapes, soft and hard gelatin capsules, suppositories, sterile parenteral solutions, packed sterile powders, etc. Examples of the pharmaceutically-acceptable carrier include lactose, glucose, sucrose, sorbitol, mannitol, corn starch, crystalline cellulose, gum arabic, calcium phosphate, alginate, calcium silicate, microcrystalline cellulose, polyvinyl pyrrolidone, tragacanth gum, gelatin, syrup, methylcellulose, carboxymethylcellulose, methyl hydroxybenzoate, propyl hydroxybenzoate, talc, magnesium stearate, inert polymers, water, mineral oil, etc. Both solid and liquid preparations may contain one or more of the above-mentioned fillers, binders, lubricants, wetting agents, disintegrators, emulsifying and suspending agents, preservatives, sweetening agents and/or aromatics. The preparations may each be formulated in such a way that after administration to patients, its active component is released in a rapid, long-acting or sustained fashion. For oral administration, the compound of the formula [I] is mixed with a carrier and diluent and is then formed into tablets, capsules or the like. For parenteral administration, the active component is dissolved in a 10% aqueous solution of glucose, isotonic saline, sterilized water or an analogous liquid and is then sealed in vials or ampuls for its administration into veins by drip infusion or injection or its intramuscular injection. Advantageously, a solubilizer, local anesthetic, preservative and/or buffer may also be incorporated in the medium. It is also feasible to lyophilize the preparation after its sealing in vials or ampuls. As other preparation forms for parenteral administration, may be mentioned those administrable percutaneously, such as ointments and cataplasms. For such parenteral administration, formed poulitices and tapes are advantageous. The preparation of this invention may contain an active component in an amount of 0.005 - 200 mg, more generally, 0.02 - 50 mg per unit dosage. The compound of the general formula [I] is effective over a wide range of dosage. For example, its dosage per day may generally range from 0.0001 mg/Kg to 200 mg/Kg. The amount of the compound to be administered actually varies depending on the type of the compound and may be determined by physician depending on the age, weight and sensitivity of each patient, the seriousness in symptom of the patient, the administration route, etc. Therefore, the above dosage range shall not be interpreted as limiting the scope of this invention. The preparation of this invention may be administered 1 - 6 times a day with 1 - 4 times being usually suitable. Although the compound of the formula [I] is by itself an effective antihypertensive agent, it may be administered, if necessary, in combination with one or more other antihypertensive agents and/or diuretics. Such additional drugs may include methyldopa, hydralazine, nifedipine, nicardipine, amyloride, propranolol, pindolol, timolol, reserpine, indapamide, hydrochlorothiazide, trichloromethiaxide, indaclinone and their analogous drugs. Physical properties and biological activities of certain compounds of this invention will hereinafter be described in the following Referential Examples, Examples and Tests. It should however be borne in mind that the present invention is not limited to the following Examples and Tests. The following Referential Examples relate to the preparation of intermediates for some compounds of the general formula [I], while the following Examples are concerned with the preparation of certain compounds of the general formula [I]. Tests will be described in the [Effects of the Invention]. Referential Example 1 : Methyl 2-(4-benzylpiperazino)-4-methylpyrimidine-5-carboxylate One hundred milliliters of a 1 M solution of sodium hydroxide in methanol were added to a suspension (60 mℓ) of 26.8 g (0.1 mol) of 1-amidino-4-benzylpiperazine sulfate [which had been synthesized in accordance with the process disclosed in J. Am. Chem. Soc., 66, 263 (1944)] in methanol, followed by a dropwise addition of 15.8 g (0.1 mol) of methyl α-methoxymethyleneacetoacetate. After stirring the resultant mixture overnight at room temperature, the precipitated sodium sulfate was filtered off. After distilling off methanol, the residue was dissolved in 500 mℓ of ethyl acetate. The resultant solution was washed twice with 100 mℓ of water. The ethyl acetate layer was washed with saturated saline and then dried with anhydrous magnesium sulfate. Upon distilling off ethyl acetate, 28.7 g of the intended compound was obtained as an orange-colored oily substance (yield: 88%). When the oily substance was left over at room temperature subsequent to its distillation under a reduced pressure, it was crystallized. Boiling point: 205 - 208°C/l mmHg(0.0013 Bar). Melting point: 38 - 40°C. Infrared absorption spectrum (neat, cm⁻¹): 1710, 1580, 1520. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.50 (4H,m), 2.63 (3H,s), 3.54 (2H,s), 3.83 (3H,s), 3.94 (4H,m), 7.32 (5H,s), 8.78 (1H,s). The following compounds were synthesized in a similar manner. (Yellow oil. The raw material was synthesized by the process of Referential Example 2.) Referential Example 2 : Methyl 2-methoxymethylene-3-oxo-n-valerate A mixture of 1.95 g of methyl 3-oxo-n-valerate [15 mmol; synthesized in accordance with the process disclosed in J. Am. Chem. Soc., 96, 1082 (1974)], 3.18 g (30 mmol) of methyl orthoformate and 4.59 g (45 mmol) of acetic anhydride was heated under reflux for 8 hours, and low b.p. fractions were then distilled off (bath temperature: 100°C). The residue was distilled under reduced pressure to obtain 1.97 g of the intended compound as a yellowish oily substance (yield: 76%). This compound was used in the synthesis of the compound of Referential Example 1. Boiling point: 86 - 90°C/3 mmHg(0.004 Bar) Infrared absorption spectrum (neat, cm⁻¹): 1710, 1625. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.07 and 1.08 (total 3H,t,J=7.0HZ), 2.68 and 2.71 (total 2H,q,J=7.0HZ), 3.74 and 3.81 (total 3H,s), 3.96 and 4.00 (total 3H,s), 7.51 and 7.56 (total 1H,s). Referential Example 3 : 2-(4-Benzylpiperazino)-4-methylpyrimidine-5-carboxylic acid Added to a 1 ℓ flask were 40 g (0.128 mol) of the ethyl 2-(4-benzylpiperazino)-4-methylpyrimidine-5-carboxylate, 11 g of KOH, 200 mℓ of H₂O and 500 mℓ of EtOH. The contents were stirred at 100°C for 0.5 hr. Thereafter, the solvent was distilled off under reduced pressure. One liter of H₂O was then added to the residue and the resulting mixture was adjusted to pH 4 with conc. hydrochloric acid. The precipitated crystals were filtered off and the filtrate was dried under reduced pressure, thereby obtaining 36 g of the intended compound as a white solid substance (yield: 98%). Melting point: 192°C. Mass spectrum (m/z): 312 (molecular ion peak). Infrared absorption spectrum (KBr tablet, cm⁻¹): 3424, 1700, 1652, 1576. ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 2.56 (3H,s), 2.77 (4H,m), 3.87 (2H,s), 4.00 (4H,m), 7.36 (5H,s), 8.71 (1H,s). Referential Example 4 : 2-(4-(Benzylpiperazino)-4-methyl-N-phenylpyrimidine-5-carboxylic acid amide Added with ice cooling to a suspension (100 mℓ) of 16.1 g (60 mmol) of 1-amidino-4-benzylpiperazine sulfate in methanol was 100 mℓ of a methanol solution of 2.4 g (60 mmol) of sodium hydroxide, followed by a dropwise addition of 200 mℓ of a methanol solution of 14.0 g (60 mmol) of α-ethoxymethyleneacetoacetic anilide (Referential Example 6). After stirring the resultant mixture overnight at room temperature, the precipitated salt was filtered off. The salt was washed with methanol. The filtrate and washing were combined together. After distilling off methanol, the residue was recrystallized from chloroform-hexane to obtain 17.26 g of the intended product as colorless crystals (yield: 74%). This compound was used for the synthesis of the compounds described in Referential Examples 10 and 11. Melting point: 176 - 177°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 3300, 1653, 1595. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.48 (4H,m), 2.53 (3H,s), 3.54 (2H,s), 3.89 (4H,m), 7.1 - 7.6 (5H,m), 7.32 (5H,s), 7.70 (1H,br), 8.39 (1H,s). Referential Example 5 : 2-(4-Benzylpiperazino)-N-ethyl-4-methylpyrimidine-5-carboxylic acid amide Placed in a 50 mℓ autoclave and reacted at 100°C for 3.5 hours were 8.16 g (25 mmol) of the methyl 2-(4-benzylpiperazino)-4-methylpyrimidine-5-carboxylate obtained in Referential Example 1, 5.64 g (125 mmol) of ethyl amine and 1.24 g (5 mmol) of a 21.8 wt.% solution of sodium methoxide in methanol. The thus-obtained reaction mixture was poured in 150 mℓ of water, followed by extraction with ethyl acetate. The ethyl acetate layer was washed with saturated saline and then dried with magnesium sulfate. Thereafter, ethyl acetate was distilled off. The residue was recrystallized from ethyl acetate-hexane to obtain 7.71 g of the intended product as light yellowish crystals (yield: 91%). Melting point: 110 - 111°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 3290, 1625, 1585. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.22 (3H,t,J=7.0HZ), 2.49 (4H,m), 2.51 (3H,s), 3.42 (2H,m), 3.55 (2H,s), 3.88 (4H,m), 5.76 (1H,m), 7.32 (5H,s), 8.30 (1H,s). The following compounds were also prepared in a similar manner. Referential Example 6 : Synthesis of α-ethoxymethyleneacetoacetic anilide A mixture of 26.6 g (0.15 mol) of acetoacetic anilide, 44.5 g (0.3 mol) of ethyl orthoformate and 45.9 g (0.3 mol) of acetic anhydride was heated under reflux for 2 hours. After cooling the reaction mixture to room temperature, hexane was added. The precipitated crystals were collected by filtration. Upon their drying, 14.3 g of the intended product was obtained as light brownish needles (yield: 41%). Melting point: 88 - 89°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 3160, 1660, 1585. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.46 (3H,t,J=7.0HZ), 2.50 (3H,s), 4.37 (2H,q,J=7.0HZ), 7.0 - 7.77 (6H), 8.46 (1H,s). Referential Example 7 : 2-(4-Benzylpiperazino)-N-(2-hydroxyethyl)-4-methylpyrimidine-5-carboxylic acid amide Reacted at 170°C for 1.5 hours were 0.34 g (1.0 mmol) of the ethyl 2-(4-benzylpiperazino)-4-methylpyrimidine-5-carboxylate and 1.22 g (20 mmol) of ethanol amine. After adding 50 mℓ of water, the resultant mixture was extracted with ethyl acetate. After washing the ethyl acetate layer with saturated saline, the ethyl acetate solution was dried with magnesium sulfate. Ethyl acetate was distilled off under reduced pressure and upon recrystallization of the residue from ethyl acetate-hexane, 0.25 g of the intended product was obtained as white crystals (yield: 72%). Melting point: 123°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 3280, 1630, 1594. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.48 (4H, m), 2.51 (3H,s), 2.46 - 2.62 (4H,m), 2.73 - 2.83 (6H,m), 6.39 (1H,brs), 7.32 (5H,s), 8.35 (1H,s). Referential Example 8 : 2-(4-Benzylpiperazino)-4-methyl-N-[2-(2'-tetrahydropyranyloxy)ethyl]pyrimidine-5-carboxylic acid amide To an ethyl acetate solution (160 mℓ) of 2.76 g (7.75 mmol) of the 2-(4-benzylpiperazino)-N-(2-hydroxyethyl)-4-methylpyrimidine-5-carboxylic acid amide obtained in Referential Example 7, 6.52 g (77.5 mmol) of 2,3-dihydropyran and 1.77 g (9.30 mmol) of p-toluenesulfonic acid monohydrate were added. The resultant mixture was stirred at room temperature for 2 days. The thus-obtained reaction mixture was washed with a saturated solution of sodium bicarbonate and was then dried with magnesium sulfate. Thereafter, ethyl acetate was distilled off under reduced pressure. The residue was purified by silica gel chromatography (eluent: ethyl acetate), thereby obtaining 3.24 g of the intended product as light yellowish crystals (yield: 95%). Melting point: 87 - 88°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 3280, 1622, 1588. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.3 - 2.0 (6H), 2.48 (4H,m), 2.52 (3H,s), 3.54 (2H,s), 3.5 - 3.9 (6H), 3.89 (4H,m), 4.56 (1H,m), 6.54 (1H,m), 7.31 (5H,s), 8.35 (1H,s). Referential Example 9 : 2-(4-Benzylpiperazino)-4-methyl-pyrimidine-5-carboxylic acid amide To 80 mℓ of pyridine containing, in a suspended state, 4.69 g (15 mmol) of the 2-(4-benzylpiperazino)-4-methylpyrimidine-5-carboxylic acid obtained in Referential Example 3, 4.45 g (37.5 mmol) of SOCl₂ was added. The resultant mixture was stirred at room temperature for 1 hour. Thereafter, 2.2 g (37.5 mmol) of 30% aqueous ammonia solution was added and the resultant mixture was stirred overnight at room temperature. After distilling off pyridine from the reaction mixture under reduced pressure, 200 mℓ of water was added, the pH of the resultant mixture was adjusted with K₂CO₃ to pH 8, and the thus-treated mixture was extracted with ethyl acetate. The ethyl acetate layer was washed with saturated saline. After drying the ethyl acetate solution with magnesium sulfate, ethyl acetate was distilled off under reduced pressure. The residue was recrystallized from chloroform-hexane to obtain 1.17 g of the intended product (yield: 25%). Melting point: 195 - 196°C. Mass spectrum (m/z): 311 (molecular ion peak). Infrared absorption spectrum (KBr tablet, cm⁻¹): 3497, 3367, 1611, 1577. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm: 2.48 (4H,m), 2.56 (3H,s), 3.54 (2H,s), 3.90 (4H,m), 7.31 (5H,s), 8.43 (1H,s). The following compounds were also synthesized in a similar manner: (The raw material was obtained in Referential Example 78.) Referential Example 10 : 4-Methyl-2-piperazino-N-tetramethylenepyrimidine-5-carboxylic acid amide Placed in a two-necked 100 mℓ flask were 1.00 g of the 2-(4-benzylpiperazino)-4-methyl-N-tetramethylenepyrimidine-5-carboxylic acid amide obtained in Referential Example 9 and 0.1 g of 10% Pd-C, followed by hydrogen substitution under reduced pressure. Then, 20 mℓ of absolute ethanol and 20 mℓ of glacial acetic acid were added and the resultant mixture was stirred at 60 - 65°C, under normal pressure for 1 hour. The reaction mixture was filtered and the catalyst was washed with ethanol. The filtrate was distilled to dryness under reduced pressure to obtain a viscous oily substance. The oily substance was purified by silica gel column chromatography (developed with EtOH), thereby obtaining 0.70 g of colorless crystals (yield: 93%). Melting point: 228°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 3420, 3300, 1625, 1585. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.82 (4H,br), 2.25 (3H,s), 2.73 (4H,m), 3.3 (4H,m), 3.70 (4H,m), 8.20 (1H,s). The following compounds were also synthesized in a similar manner. Referential Example 11 : 6-Ethyl-2-(4-benzylpiperazino)pyrido[4,3-d]pyrimidin-5(6H)-one After washing 240 mg of sodium hydride (60% in oil, 6 mmol) with hexane, it was suspended in 3 mℓ of N,N-dimethylformamide (DMF). Thereafter, a DMF solution (10 mℓ) of 1.7 g (5 mmol) of 2-(4-benzylpiperazino)-N-ethyl-4-methylpyrimidine-5-carboxylic acid amide (Referential Example 5) was added and the reactants were reacted at 150°C for 1.5 hours. After distilling off DMF under reduced pressure, 100 mℓ of water was added, followed by extraction with ethyl acetate. The ethyl acetate layer was washed with saturated saline and dried with magnesium sulfate, and ethyl acetate was distilled off under reduced pressure. The residue was recrystallized from ethyl acetatehexane to obtain 1.5 g of the intended product as light yellowish crystals (yield: 87%). Melting point: 116 - 118°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 1660, 1638. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.32 (3H,t,J=7HZ), 2.50 (4H,t,J=6HZ), 3.54 (2H,s), 3.76 - 4.08 (6H,m), 6.24 (1H,d,J=7HZ), 7.23 (1H,d,J=7HZ), 7.31 (5H,s), 9.20 (1H,s). The following compounds were also synthesized in a similar manner. Referential Example 12 : 2-(4-Benzylpiperazino)-N-ethyl-N-ethyloxaloyl-4-methylpyrimidine-5-carboxylic acid amide Five milliliters of a tetrahydrofuran solution of 0.335 g (1 mmol) of the 2-(4-benzylpiperazino)-N-ethyl-4-methylpyrimidine-5-carboxylic acid amide obtained in Referential Example 5 were cooled in an ice bath, to which 0.048 g (60% in oil, 1.2 mmol) of sodium hydride was added. The resultant mixture was stirred for 10 minutes. Thereafter, 1 ml of a tetrahydrofuran solution of 0.15 g (1.1 mmol) of ethyloxalyl chloride was added dropwise. The thus-prepared mixture was stirred at room temperature for 1 hour and then at 70°C for further 4 hours. The thus-obtained reaction mixture was poured in 50 g of ice water, followed by extraction with ethyl acetate. The organic layer was washed with saturated saline and then dried with sodium sulfate. Thereafter, the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane = 3/2) to obtain 0.306 g of the intended product as a light blue oil (yield: 71%). Infrared absorption spectrum (neat, cm⁻¹): 1740, 1712, 1672, 1590. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.18 (3H,t,J=7.2Hz), 1.24 (3H,t,J=7.2Hz), 2.47 (3H,s), 2.51 (4H,m), 3.58 (2H,s), 3.72 - 4.16 (8H,m), 7.34 (5H,s), 8.23 (1H,s). Referential Example 13 : Ethyl 2-(4-benzylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-7-carboxylate A mixture of 0.3 g (0.68 mmol) of the 2-(4-benzylpiperazino)-N-ethyl-N-ethyloxaloyl-4-methylpyrimidine-5-carboxylic acid amide obtained in Referential Example 12, 0.027 g (60% in oil, 0.68 mmol) of sodium hydride and 5 ml of dimethylformamide was reacted at 120°C for 2 hours. Fifty grams of ice water were added, followed be extraction with ethyl acetate. The oil layer was washed with saturated saline and was then dried with sodium sulfate. Ethyl acetate was distilled off under reduced pressure and the residue was purified by silica gel column chromatography (eluent: ethyl acetate), thereby obtaining 0.095 g of a light yellowish oil (yield: 33%). This compound was used for the preparation of the compound described in Referential Example 14. Infrared absorption spectrum (neat, cm⁻¹): 1730, 1660, 1613, 1574. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.35 (3H,t,J=7Hz), 1.42 (3H,t,J=7Hz), 2.51 (4H,t,J=5.5Hz), 3.55 (2H,s), 3.98 (4H,t,J=5.5Hz), 4.26 (2H,q,J=7Hz), 4.40 (2H,q,J=7Hz), 6.75 (1H,s), 7.37 (5H,s), 9.22 (1H,s). Mass spectrum: 421 (molecular ion peak). Referential Example 14 : 5,6-Dihydro-6-ethyl-8-methyl-5-oxo-2-piperazinopyrido[4,3-d]pyrimidine-5(6H)-one Added to 300 mg (0.83 mmol) of the 2-(4-benzylpiperazino)-6-ethyl-8-methylpyrido[4,3-d]pyrimidine-5(6H)-one obtained in Referential Example 11 were 6 mℓ of ethanol, 2 mℓ of acetic acid and 30 mg of 10% Pd-C. The resultant mixture was stirred at 45°C for 3.5 hours in a hydrogen atmosphere. The Pd-C was removed from the reaction mixture, followed by concentration under reduced pressure. The concentrate was added with 20 mℓ of water, to which potassium carbonate was added until no foams were developed. The resultant mixture was extracted three times with 50 mℓ of chloroform. The chloroform layer was dried with sodium sulfate and then concentrated under reduced pressure, thereby obtaining 200 mg of 6-ethyl-8-methyl-2-piperazinopyrido[4,3-d]pyrimidine-5(6H)-one as colorless crystals (yield: 88%). Melting point: 170 - 172°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 1657, 1618, 1578. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.33 (3H,t,J=7.2Hz), 1.66 (1H,s), 2.17 (3H,d,J=1.3Hz), 2.94 (4H,m), 3.97 (6H,m), 7.10 (1H,q,J=1.3Hz), 9.24 (1H,s). The following compounds were also prepared in a similar manner. Referential Example 15 : 2-(4-Benzylpiperazino)-6-(2-(2'-tetrahydropyranyloxy)ethyl)pyrido[4,3-d]pyrimidine-5(6H)-one After washing 240 mg of sodium hydride (60% in oil, 6 mmol) with hexane, it was suspended in 2 mℓ of DMF. Thereafter, a DMF solution (10 mℓ) of 1.76 g (3 mmol) of 2-(4-benzylpiperazino)-4-methyl-N-(2-(2'-tetrahydropyranyloxy)ethyl)pyrimidine-5-carboxylic acid amide (Referential Example 8) was added. The resultant mixture was stirred at 150°C for 7 hours. After driving off DMF under reduced pressure, 100 mℓ of water was added, followed by extraction with ethyl acetate. The ethyl acetate layer was washed with saturated saline and dried with MgSO₄, and the solvent was then distilled off under reduced pressure. The residue was purified by silica gel column chromatography (eluent: ethyl acetate) to obtain 0.86 g of the intended product as a yellowish oily substance (yield: 64%). Infrared absorption spectrum (neat, cm⁻¹): 1650, 1615, 1573, 1540, 1505. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.3 - 2.0 (6H,m), 2.52 (4H,m), 3.56 (2H,s), 3.4 - 4.3 (10H, m), 4.56 (1H, m), 6.26 (1H,d,J=7.4Hz), 7.33 (5H,s), 7.40 (1H,d,J=7.4Hz), 9.22 (1H,s). Referential Example 16 : 2-Piperazino-6-(2-hydroxyethyl)pyrido[4,3-d]pyrimidine-5(6H)-one An ethanol-acetic acid solution [15 mℓ, ethanol/acetic acid = 2 (volume ratio] of 450 mg (1 mmol) of the 2-(4-benzylpiperazino)-6-(2(2'-tetrahydropyranyloxy)ethyl)pyrido[4,3-d]pyrimidine-5(6H)-one obtained in Referential Example 15 was added with 10% Pd-C, to which hydrogen was introduced under atmospheric pressure at 80°C for 6.5 hours to effect debenzylation. After the reaction, the catalyst was filtered off and the filtrate was concentrated under reduced pressure to obtain the above-identified compound. Referential Example 17 : 2-(4-Benzylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbaldehyde Dissolved in 4.0 mℓ of diethylformamide was 0.4 g of the 2-(4-benzylpiperazino)-4-methylpyrimidine-5-carboxylic acid obtained in Referential Example 3. At room temperature, 0.5 mℓ of phosphorus oxychloride was added dropwise. Thereafter, the contents were heated and reacted at 100°C for 1.5 hours. After cooling, the reaction mixture was poured in an aqueous solution of sodium carbonate to neutralize same, followed by extraction with chloroform. After washing the chloroform layer with water, it was dried with anhydrous magnesium sulfate. Chloroform was distilled off under reduced pressure to obtain 0.29 g of the intended product (yield: 60%). Melting point: 151.9°C. Mass spectrum: 377 (molecular ion peak). Infrared absorption spectrum (KBr tablet, cm⁻¹): 1690, 1662, 1628, 1570. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.39 (3H,t,J=7Hz), 2.52 (4H,m), 3.58 (2H,s), 4.02 (4H,m), 4.05 (2H,q,J=7Hz), 7.33 (5H,s), 8.18 (1H,s), 9.19 (1H,s), 10.33 (1H,s). Referential Example 18 : 2-(4-Benzylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbaldehydooxime Dissolved in dimethylsulfoxide was 3.0 g of the 2-(4-benzylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbaldehyde obtained in Referential Example 17. The solution was heated to 50°C, at which an aqueous solution (10 mℓ) containing 0.83 g of hydroxylamine hydrochloride and 0.7 g of potassium hydroxide was added dropwise. Thereafter, the contents were stirred and reacted for further 30 minutes. The reaction mixture was poured in water, and the precipitate was collected by filtration and then washed with methanol. It was dried under reduced pressure to obtain 2.65 g of light yellowish crystals (yield: 82%). Melting point: 226.6 °C. Mass spectrum: 392 (molecular ion peak). Infrared absorption spectrum (KBr tablet, cm⁻¹): 3355, 3174, 1654, 1645, 1582. ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 1.32 (3H,t,J=7Hz), 2.56 (4H,brs), 3.62 (2H,s), 3.80 - 4.10 (6H,m), 7.32 (5H, s), 8.06 (1H,s), 8.42 (1H,s), 9.06 (1H,s), 10.87 (1H,s). Referential Example 19 : Preparation of 2-(4-benzylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidinecarbonitrile Added to 100 g of phosphorus oxychloride was 3.13 g of the 2-(4-benzylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbaldehydooxime obtained in Referential Example 18. The resultant mixture was heated under reflux for 0.5 hr. Excess phosphorus oxychloride was distilled off. Chloroform and a 10% aqueous solution of sodium hydroxide were added to the reaction mixture to neutralize same, followed by extraction with chloroform. The chloroform layer was dried with anhydrous magnesium sulfate. Chloroform was distilled off under reduced pressure and the extract was recrystallized from toluene, thereby obtaining 2.2 g of light yellowish crystals (yield: 74%). Melting point: 218.3°C. Mass spectrum: 374 (molecular ion peak). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.39 (3H,t,J=7Hz), 2.53 (4H,m), 3.57 (2H,s), 3.90 - 4.20 (6H,m), 7.33 (5H,s), 7.87 (1H,s), 9.15 (1H,s). Referential Example 20 : 2-(4-Benzyloxycarbonylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbaldehyde Dissolved in 5.0 mℓ of tetrahydrofuran was 0.55 g of the 2-(4-benzylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbaldehyde obtained in Referential Example 17, to which 0.31 g of benzyl chlorocarbonate was added dropwise at room temperature. The resultant mixture was stirred at 50°C for further 3 hours. After allowing the reaction mixture to cool, tetrahydrofuran was distilled off under reduced pressure and the residue was washed with n-hexane to obtain 0.55 g of light yellowish crystals (yield: 91%). Melting point: 208.0 - 208.9°C. Mass spectrum: 421 (molecular ion peak). Infrared absorption spectrum (nujol, cm⁻¹): 1711, 1691, 1657. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.41 (3H,t,J=7Hz), 3.62 (4H,m), 4.01 (6H,m), 5.20 (2H,s), 7.38 (5H,s), 8.23 (1H,s), 9.24 (1H,s), 10.56 (1H,s). The following compound was synthesized in the same manner except that the reaction was carried out at 50°C for 12 hours by using 2-(4-benzyl-piperazino)-4-methylthiopyrimidine-5-carboxylic acid diethylamide obtained in Referential Example 68 in place of 2-(4-benzylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbaldehyde. Referential Example 21 : 2-(4-Benzyloxycarbonylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbaldehydooxime Dissolved in 20 mℓ of chloroform was 1.0 g of the 2-(4-benzyloxycarbonylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbaldehyde obtained in Referential Example 20, to which an aqueous solution of 0.25 g of hydroxylamine hydrochloride and 0.24 g of potassium hydroxide was added at room temperature. Thereafter, the resulting mixture was heated with stirring at 60°C for 2.5 hours. After allowing the reaction mixture to cool down, the chloroform layer was collected and dried with anhydrous magnesium sulfate. Chloroform was distilled off under reduced pressure and the resultant crude crystals were washed with n-hexane to obtain 0.81 g of light yellowish crystals (yield: 81%). Melting point: 170.9°C. Mass spectrum: 436 (molecular ion peak). Infrared absorption spectrum (nujol, cm⁻¹): 1645, 1583, 1491, 1348. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.37 (3H,t,J=7.0Hz), 3.61 (4H,m), 3.96 (6H,m), 5.19 (2H,s), 7.36 (5H,s), 7.93 (1H,s), 8.61 (1H,s), 9.25 (1H,s). Referential Example 22 : 2-(4-Benzyloxypiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbonitrile The above-identified compound was synthesized in the same manner as in Referential Example 20 except that the reaction was carried out at room temperature for 12 hours by using 2-(4-benzylpiperazino)-5,6-dihydro-6-ethyl-5-oxo[4,3-d]pyrimidine-8-carbonitrile (Referential Example 19) instead of 2-(4-benzylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbaldehyde (slightly yellowish crystals, yield: 79%). Melting point: 184 - 186°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 2239 (CN), 1709, 1662, 1623, 1580. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.40 (3H,t,J=7.2Hz), 3.60 (4H,m), 4.10 (6H,m), 5.20 (2H,s), 7.39 (5H,s), 7.89 (1H,s), 9.20 (1H,s). Incidentally, the present compound may also be synthesized by dehydrating the compound of Referential Example 21 in the same manner as in Referential Example 19. Referential Example 23 : 5,6-Dihydro-6-ethyl-5-oxo-2-piperazinopyrido[4,3-d]pyrimidine-8-carbaldehyde Dissolved in a 25% hydrogen bromide solution of acetic acid was 0.2 g of the 2-(4-benzyloxycarbonylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbaldehyde obtained in Referential Example 20. The resulting mixture was stirred at room temperature for 1 hour. Hydrogen bromide, acetic acid and resulting benzyl bromide were distilled off under reduced pressure. After neutralizing the residue with a saturated aqueous solution of sodium carbonate, the mixture was extracted with chloroform and the chloroform layer was dried with anhydrous magnesium sulfate. Chloroform was distilled off under reduced pressure to obtain 0.13 g of light yellowish crystals (yield: 95%). Melting point: over 300°C. Infrared absorption spectrum (nujol, cm⁻¹): 3400, 1688, 1655. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.40 (3H,t,J=7.0Hz), 2.95 (4H,m), 4.08 (6H,m), 8.19 (1H,s), 9.20 (1H,s), 10.55 (1H,s). The following compound was also synthesized in a similar manner. (The raw material was synthesized in Referential Example 20.) Referential Example 24 : 5,6-Dihydro-6-ethyl-5-oxo-2-piperazinopyrido[4,3-d]pyrimidine-8-carbonitrile To 0.4 g of the 2-(4-benzyloxycarbonylpiperazino)-5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-8-carbonitrile obtained in Referential Example 22, 15 mℓ of ethanol, 1 mℓ of acetic acid and 0.2 g of 5% Pd-C were added. The resulting mixture was stirred at 50°C for 2 hours in a hydrogen atmosphere of normal pressure. Pd-C was removed from the reaction mixture by filtration and the resultant filtrate was concentrated under reduced pressure. The concentrate was added with 20 mℓ of water and 1 mℓ of 2M-HCℓ and then washed with chloroform. The water layer was neutralized with potassium carbonate and then extracted with chloroform. The chloroform solution was dried with anhydrous sodium sulfate and chloroform was then driven off under reduced pressure, thereby obtaining 80 mg of slightly yellowish crystals (yield: 29%). Melting point: 204 - 206°C (decomposed). Infrared absorption spectrum (KBr tablet, cm⁻¹): 2230 (CN), 1671, 1620, 1578. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.40 (3H,t,J=7.2Hz), 1.65 (1H,s), 2.95 (4H,m), 4.00 (6H,m), 7.88 (1H,s), 9.19 (1H,s). Referential Example 25 : 5,6-Dihydro-6-ethyl-5-thioxo-2-piperazinopyrido[4,3-d]pyrimidine In pyridine (20 mℓ), 2 g (7.7 mmol) of the 5,6-dihydro-6-ethyl-5-oxo-2-piperazinopyrido[4,3-d]pyrimidine obtained in Referential Example 14 and 6 g (27 mmol) of phosphorus pentasulfide were reacted at 100°C for 3 hours. Thereafter, pyridine was distilled off under reduced pressure and the residue was taken up in hot water. The resultant aqueous solution was extracted with chloroform. The chloroform layer was dried with anhydrous magnesium sulfate, followed by its concentration. The residue was purified by silica gel column chromatography (eluent: chloroform/methanol = 95/5) to obtain 0.3 g of the intended product (yield: 14%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.44 (3H,t,J=7.0Hz), 3.52 (4H,m), 3.98 (2H,m), 4.38 (4H,m), 6.58 (1H,d,J=7.5Hz), 7.55 (1H,d,J=7.5Hz), 9.79 (1H,s). Referential Example 26 : 2,4-Dichloro-5-chlorocarbonylpyrimidine Twenty grams of 2,4-dihydroxypyrimidine-5-carboxylic acid and 220 mℓ of phosphorus oxychloride were reacted under reflux for 10 hours. Thereafter, the reaction mixture was cooled to room temperature and 100 g of phosphorus pentachloride was added. The contents were again reacted at 120°C for 7 hours. After completion of the reaction, phosphorus oxychloride was distilled off and the reaction product was purified by its distillation under reduced pressure (b.p. 130 - 140°C/l mmHg, yield: 35%). Referential Example 27 : 2-4-Dichloro-N-ethyl-5-carboxylic acid amide To a solution of 1.02 g (4.8 mmol) of the 2,4-dichloro-5-chlorocarbonylpyrimidine synthesized in Referential Example 26 in methylene chloride (5 mℓ), 0.6 mℓ of ethylamine was added at -20°C. The resultant mixture was then reacted at room temperature for 2 hours. Water was added to the reaction mixture, followed by extraction with methylene chloride. After drying the methylene chloride layer with magnesium sulfate, methylene chloride layer was distilled off under reduced pressure to obtain 0.97 g of the intended product as yellowish solid (yield: 91%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.28 (3H,t,J=7.2Hz), 3.52 (2H,m), 8.92 (1H,s). Referential Example 28 : 2-Chloro-N-ethyl-4-methylthio-5-carboxylic acid amide An NaSCH₃/MeOH solution, which had been prepared on the side, was added dropwise to 1.15 g (5.2 mmol) of the 2,4-dichloro-N-ethyl-5-carboxylic acid amide prepared in Referential Example 27. Reaction course was monitored by TLC. Upon consumption of the raw material, the reaction mixture was concentrated and was then added with water, followed by extraction with chloroform. The chloroform layer was dried with anhydrous magnesium sulfate. Under reduced pressure, chloroform was distilled off. The residue was purified by silica gel column chromatography to obtain 0.7 g of the intended product (yield: 54%). Melting point: 188 - 190°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.27 (3H,t,J=7.4Hz), 2.59 (3H,s), 3.50 (2H,d.q,J=5.7 and 7.4Hz); 6.12 (1H,br.t), 8.47 (1H,s). The following compound was synthesized in the same manner except that the ethyl 2-(4-benzylpiperazino)-4-chloropyrimidine-5-carboxylate obtained in Referential Example 63 was used in place of 2,4-dichloro-N-ethyl-5-carboxylic acid amide. Referential Example 29 : 2-(4-Benzylpiperazino)-N-ethyl-4-methylthio-5-carboxylic acid amide One milliliter of benzylpiperazine was added to 10 mℓ of a butanol solution in which 1.0 g of the 2-chloro-N-ethyl-4-methylthio-5-carboxylic acid amide synthesized in Referential Example 28 was dissolved. The resultant mixture was refluxed for 2 hours. The reaction mixture was cooled, the precipitated benzylpiperazine hydrochloride was filtered off, and the filtrate was then concentrated under reduced pressure. The concentrate was recrystallized from ethyl acetate, thereby obtaining 600 mg of the intended product as colorless crystals (yield: 41%). Melting point: 145 - 148°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.23 (3H,t,J=7.2Hz), 2.46 (3H,s), 2.56 (4H,m), 3.46 (2H,d.q,J=5.7 and 7.2Hz), 3.55 (2H,s), 3.90 (4H,m), 6.20 (1H,br.t), 8.36 (1H,s). Referential Example 30 : N-Ethyl-2-piperazino-5-carboxylic acid amide An ethanol solution (10 mℓ) of 100 mg of the 2-(4-benzylpiperazino)-N-ethyl-4-methylthio-5-carboxylic acid amide synthesized in Referential Example 29 was added with 500 mg of Raney nickel and was then refluxed for 2.5 hours. Raney nickel was filtered off from the reaction mixture and the filtrate was concentrated under reduced pressure. The concentrate was added with 10 mℓ of methylene chloride and 1 mℓ of water. The resultant mixture was then allowed to separate into layers. After drying the methylene chloride layer with anhydrous sodium sulfate, it was concentrated to obtain 40 mg of the intended product as a colorless oil (yield: 64%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.23 (3H,t,J=7.0Hz), 2.95 (4H,m), 3.45 (2H,d.q,J=5.3 and 7.0Hz), 3.85 (4H,m), 6.20 (1H,br.t), 8.71 (2H,s). Referential Example 31 : 1,4,5,6-Tetrahydro-6-ethyl-5-oxo-2-(4-benzylpiperazino)pyrido[4,3-d]pyrimidine Added at room temperature to a suspension of 0.80 (21 mmol) of lithium aluminum hydride in THF (20 mℓ) was 1.5 g of 5,6-dihydro-6-ethyl-5-oxo-2-(4-benzylpiperazino)pyrido[4,3-d]pyrimidine (Referential Example 11). After refluxing the reaction mixture for 4 hours, the reaction mixture was added with water to decompose excess lithium aluminum hydride. An aqueous solution of sodium hydroxide and chloroform were added to the resultant mixture to extract the latter. After washing the chloroform layer with water, it was dried with anhydrous magnesium sulfate and was then concentrated to obtain 1.4 g of light yellowish crystals. The crude crystals were immersed in ethyl acetate to obtain 1.1 g of 1,4,5,6-Tetrahydro-6-ethyl-5-oxo-2-(4-benzylpiperazino)pyrido[4,3-d]pyrimidine as colorless crystals (yield: 72%). Melting point: 200 - 203°C. Mass spectrum: 351 (M⁺). Infrared absorption spectrum (CHCℓ₃ solution, cm⁻¹): 1640, 1565, 1529. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.30 (3H,t,J=7Hz), 2.50 (4H,m), 3.54 (6H,m), 3.90 (2H,q,J=7Hz), 4.42 (2H,s), 4.87 (1H,brs), 5.92 (1H,d,J=7.5Hz), 7.03 (1H,d,J=7.5Hz), 7.32 (5H,m). The following compound was also synthesized in a similar manner. Referential Example 32 : 1,4,5,6-Tetrahydro-6-ethyl-5-oxo-2-piperazinopyrido[4,3-d]pyrimidine Dissolved in 20 mℓ of ethanol was 1.0 g of the 1,4,5,6-tetrahydro-6-ethyl-5-oxo-2-(4-benzylpiperazino)pyrido[4,3-d]pyrimidine obtained in Referential Example 31, followed by an addition of 10% Pd-C. The resultant mixture was stirred at 70°C for 2.5 hours in a hydrogen atmosphere. After removal of the catalyst by filtration, the filtrate was concentrated to obtain 0.7 g of 1,4,5,6-Tetrahydro-6-ethyl-5-oxo-2-piperazinopyrido[4,3-d]pyrimidine as crystals (yield: 95%). Melting point: 117 - 120°C (decomposed, deliquescent). Mass spectrum: 247 (M⁺). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.30 (3H,t,J=7Hz), 2.90 (4H,m), 3.55 (4H,m), 3.88 (2H,q,J=7Hz), 4.40 (2H,s), 5.98 (1H,d,J=7.5Hz), 7.03 (1H,d,J=7.5Hz). The following compound was also synthesized in a similar manner. Referential Example 33 : Ethyl 3-ethylaminopropionate Dissolved in 500 mℓ of ethanol was 50 g (0.50 mol) of ethyl acrylate. While stirring the thus-prepared solution with ice cooling, a liquid mixture of 36 g (0.55 mol) of a 70% aqueous solution of ethylamine and 100 mℓ of ethanol was added dropwise over 3.5 hours. After allowing the reaction to proceed for further 3 hours, the solvents were distilled off. The residue was distilled under reduced pressure to obtain 50.5 g of the intended product as colorless liquid (yield: 70%). Boiling point: 65°C/10 mmHg. Infrared absorption spectrum (neat, cm⁻¹): 3320 (broad), 1735. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.0 - 1.4 (6H,m), 2.4 - 3.0 (6H,m), 4.16 (2H,q,J=7.0Hz). Referential Example 34 : Ethyl N-ethoxycarbonylacetyl-3-ethylaminopropionate While stirring with ice-cooling a mixture of 45 g (0.30 mol) of the ethyl 3-ethylaminopropionate obtained in Referential Example 33, 37.3 g (0.27 mol) of potassium carbonate, 250 mℓ of toluene and 250 mℓ of water, 67.7 g (0.45 mol) of ethylmalonyl chloride was dropped over 0.5 hour. After mixing the resultant mixture at room temperature for further 3 hours, the reaction mixture was allowed to separate into layers. The toluene layer was washed successively with 5% hydrochloric acid, saturated aqueous solution of sodium bicarbonate, and saturated saline, and was then dried with anhydrous magnesium sulfate. Toluene was distilled off under reduced pressure to obtain 64.3 g of the intended product as colorless liquid (yield: 83%). Infrared absorption spectrum (neat, cm⁻¹): 1735, 1648. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.1 - 1.3 (6H), 2.64 (2H), 3.2 - 3.8 (6H), 4.0 - 4.2 (4H). Referential Example 35 : 3-Carboethoxy-1-ethylpiperidine-2,4-dione To an ethanol solution of sodium ethoxide which had been synthesized by adding 5.8 g of metallic sodium to 300 mℓ of ethanol, 62.2 g of ethyl N-ethoxycarbonylacetyl-3-ethylaminopropionate (Referential Example 34) was added. The resultant mixture was refluxed for 4 hours. After allowing the reaction mixture to cool down, ethanol was distilled off. Ethyl acetate and a dilute aqueous solution of hydrogen chloride were added. The resulting mixture was shaken. After washing the organic layer with water, it was dried and concentrated to obtain 36.3 g of 3-carboethoxy-1-ethylpiperidine-2,4-dione as an oily substance (yield: 71%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.28 (6H,m), 2.66 (2H,m), 3.44 (4H,m), 4.32 (2H,m). Referential Example 36 : 1-Ethylpiperidine-2,4-dione Added to 36.0 g of 3-carboethoxy-1-ethylpiperidine-2,4-dione (Referential Example 35) was 300 mℓ of a 10% aqueous solution of hydrochloric acid. The resultant mixture was refluxed for 40 minutes. After allowing the reaction mixture to cool down, it was extracted with chloroform. The chloroform layer was washed with water, dried and then concentrated, thereby obtaining 16.6 g of 1-ethylpiperidine-2,4-dione as a light yellowish oily substance (yield: 70%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.20 (3H,t,J=7Hz), 2.64 (2H,t,J=7Hz), 3.36 (2H,s), 3.54 (4H,m). Referential Example 37 : 1-Ethyl-3-methoxymethylenepiperidine-2,4-dione Added to 8.3 g of 1-ethylpiperidine-2,4-dione were 11 g of methyl orthoformate and 20 mℓ of acetic anhydride. The resultant mixture was refluxed for 7 hours. After allowing the reaction mixture to cool down, excess methyl orthoformate and acetic anhydride were distilled off under reduced pressure. The brown residue was distilled under reduced pressure in a Kugelroll apparatus (0.5 mmHg; bath temperature: 200 - 250°C) to obtain 2.7 g of 1-ethyl-3-mehtoxymethylenepiperidine-2,4-dione as crystals (yield: 25%). The crystals were recrystallized from a mixed solvent of ethyl acetate and hexane to obtain needles. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.20 (3H,m), 2.64 (2H,t,J=7Hz), 3.50 (4H,m), 4.12 (3H,s), 7.86 (1H, two singlets). Referential Example 38 : 2-(4-Benzylpiperazino)-6-ethyl-5-oxo-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine To a suspension which had been obtained by adding 1.56 g of 1-amidino-4-benzylpiperazine sulfate to an ethanol solution of 0.23 g of sodium hydroxide, 1.07 g of 1-ethyl-3-methoxymethylenepiperidine-2,4-dione (Referential Example 37) was added. The resultant mixture was refluxed for 2 hours. After distilling off ethanol, water was added to the residue, followed by extraction with chloroform. After drying the chloroform layer, it was concentrated to obtain 1.4 g of 2-(4-benzylpiperazino)-6-ethyl-5-oxo-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine (yield: 69%). Melting point: 128 - 130°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.20 (3H,t,J=7Hz), 2.50 (4H,m), 2.94 (2H,t,J=8Hz), 3.55 (6H,m), 3.92 (4H,m), 7.32 (5H,m), 8.92 (1H,s). Referential Example 39 : 6-Ethyl-5-oxo-2-piperazino-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine Dissolved in 20 mℓ of ethanol was 0.70 g of 2-(4-benzylpiperazino)-6-ethyl-5-oxo-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine (Referential Example 38), followed by an addition of 10% Pd-C. The resultant mixture was stirred at 60°C for 4 hours in a hydrogen atmosphere. After allowing the reaction mixture to cool down, the catalyst was filtered off and the filtrate was concentrated to obtained 0.50 g of 6-ethyl-5-oxo-2-piperazino-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine as crystals (yield: 96%). The crystals were purified by their immersion in ethyl acetate. Melting point: 205 - 210°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.20 (3H,t,J=7Hz), 3.00 (6H,m), 3.60 (4H,m), 3.94 (4H,m), 8.84 (1H,s). Referential Example 40 : Ethyl 4-chloro-2-ethoxymethyleneacetoacetate After heating and stirring 10 g (60.7 mmol) of ethyl 4-chloroacetoacetate, 18 g (121 mmol) of ethyl orthoformate and 25 g (245 mmol) of acetic anhydride at 110°C for 3 hours, excess ethyl orthoformate and acetic anhydride were distilled off under reduced pressure and the residue was recrystallized from hexane to obtain 12.1 g of a solid substance as needles (yield: 90%). Melting point: 86.5°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.35 (3H,t,J=7Hz), 1.44 (3H,t,J=7Hz), 4.30 (2H,q,J=7Hz), 4.33 (2H,q,J=7Hz), 4.56 (2H,s), 7.88 (1H,s). Infrared absorption spectrum (KBr tablet, cm⁻¹): 2900, 2830, 1686, 1670, 1575, 1250, 1018. Referential Example 41 : Ethyl 4-chloromethyl-2-(4-benzylpiperazino)pyrimidine-5-carboxylate A solution, which had been prepared by dissolving 1.5 g of NaOH in 15 mℓ of H₂O, was added to a suspension of 9.7 g (36.4 mmol) of 1-amidino-4-benzylpiperazine sulfate and 185 mℓ of THF to neutralize the suspension. Thereafter, a solution of 8 g (36.4 mmol) of the ethyl 4-chloro-2-ethoxymethyleneacetoacetate obtained in Referential Example 40 in 200 mℓ of THF was added dropwise at 20°C. After completion of the dropwise addition, 300 mℓ of ether was added. The resultant mixture was washed three times with water. After drying the organic layer with anhydrous MgSO₄, the solvent was distilled off under reduced pressure to obtain 11.8 g of the intended product with a light yellowish color (yield: 86.7%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.37 (3H,t,J=7Hz), 2.51 (4H,t,J=6Hz), 3.75 (2H,s), 3.97 (4H,t,J=6Hz), 4.34 (2H,q,J=7Hz), 4.88 (2H,s), 7.32 (5H,s), 8.87 (1H,s). Infrared absorption spectrum (neat, cm⁻¹): 2873, 2780, 1706, 1582, 1526, 1445, 1350, 1250, 1090, 1000, 742, 696. Referential Example 42 : 2-(4-Benzylpiperazino)-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Dissolved in 10 mℓ of ethanol was 2.25 g (6 mmol) of ethyl 4-chloromethyl-2-(4-benzylpiperazino)pyrimidine-5-carboxylate (Referential Example 41), followed by an addition of 10 mℓ (59 mmol) of a 30% aqueous NH₄OH solution at 20°C. The resultant mixture was stirred for 12 hours. The reaction mixture was poured in a 10% aqueous NaHCO₃ solution, followed by extraction with CHCℓ₃. The solvent was then distilled off and the residue was recrystallized from toluene. Yield: 0.70 g (38%). Melting point: 172°C. ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 2.45 (4H,t,J=6Hz), 3.50 (2H,s), 3.83 (4H,t,J=6Hz), 4.20 (2H,s), 7.30 (5H,s), 8.20 (1H,br.s), 8.57 (1H,s). Infrared absorption spectrum (nujol, cm⁻¹): 2900, 1715, 1674, 1607, 1562, 1218, 1145, 730, 720. Referential Example 43 : 2-Piperazino-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine While heating at 60°C 1.6 g (5.18 mmol, Referential Example 42) of 2-(4-benzylpiperazino)-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine, 0.16 g of 10% Pd-C and 30 mℓ of AcOH, H₂ was bubbled. One hour later, Pd-C was filtered off and then the solvent was distilled off. The residue was suspended in a 10% aqueous NaHCO₃ solution. Insoluble matter was collected by filtration. Toluene was added to the solid and then toluene was distilled off under reduced pressure to obtain 0.75 g of the intended product (yield: 66%; oil). ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 2.80 (4H,br.s), 3.24 (1H,br.s), 3.78 (4H,br.s), 4.23 (2H,s), 8.18 (1H,br.s), 8.58 (1H,s). Infrared absorption spectrum (KBr tablet, cm⁻¹): 3210, 3100, 2920, 2880, 1700, 1612, 1260, 1150, 980. Referential Example 44 : 6-Ethyl-2-(4-benzylpiperazino)-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Dissolved in 10 mℓ of ethanol was 1.0 g (2.7 mmol, Referential Example 41) of ethyl 4-chloromethyl-2-(4-benzylpiperazino)pyrimidine-5-carboxylate, followed by an addition of 5 g (59 mmol) of a 70% aqueous solution of ethylamine at 20°C. The resultant mixture was stirred for 2 hours and was stirred for further 0.5 hour at 80°C. After completion of the reaction, the reaction mixture was poured in water, neutralized with a 10% aqueous NaHCO₃ solution, and then extracted with ether. After drying the organic layer, the solvent was distilled off and the residue was recrystallized from toluene/hexane [yield: 0.82 g (91%)]. Melting point: 159.2°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.22 (3H,t,J=7Hz), 2.50 (4H,t,J=6Hz), 3.55 (2H,s), 3.59 (2H,q,J=7Hz), 3.93 (4H,t,J=6Hz), 4.18 (2H,s), 7.32 (5H,s), 8.64 (1H,s). Infrared absorption spectrum (nujol, cm⁻¹): 2900, 1666, 1624, 1566, 1280, 1148, 1000, 975, 795, 733. Each of the following four compounds was also obtained in a similar manner. 6-Methyl-2-(4-benzylpiperazino)-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Yield: 94%. Melting point: 178 - 179°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.52 (4H,m), 3.15 (3H,s), 3.58 (2H,s), 3.96 (4H,m), 4.20 (2H,s), 7.36 (5H,m), 8.65 (1H,s). Infrared absorption spectrum (CHCℓ₃, cm⁻¹): 1685, 1618, 1522, 1350. 6-Isopropyl-2-(4-benzylpiperazino)-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Yield: 39%. Melting point: 173 - 174°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.25 (6H,d,J=7Hz), 2.52 (4H,m), 3.58 (2H,s), 3.96 (4H,m), 4.16 (2H,s), 4.64 (1H,sept.,J=7Hz), 7.36 (5H,m), 8.66 (1H,s). Infrared absorption spectrum (CHCℓ₃, cm⁻¹): 1680, 1618, 1530, 1345. 6-n-Propyl-2-(4-benzylpiperazino)-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Yield: 67%. Melting point: 148 - 150°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 0.95 (3H,t,J=7Hz), 1.65 (2H,hextet,J=7Hz), 2.52 (4H,m), 3.52 (2H,t,J=7Hz), 3.58 (2H,s), 3.96 (4H,m), 4.21 (2H,s), 7.37 (5H,s), 8.68 (1H,s). Infrared absorption spectrum (CHCℓ₃, cm⁻¹): 3000, 1680, 1610, 1520, 1342, 1000. 6-n-Butyl-2-(4-benzylpiperazino)-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Yield: 62%. Melting point: 144 - 146°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 0.96 (3H,t,J=7Hz), 1.16 - 1.80 (4H), 2.52 (4H,m), 3.57 (2H,s), 3.57 (2H,t,J=7Hz), 3.96 (4H,m), 4.20 (2H,s), 7.37 (5H,s), 8.68 (1H,s). Infrared absorption spectrum (CHCℓ₃, cm⁻¹): 3010, 1680, 1610, 1520, 1342, 1000. Referential Example 45 : 6-Ethyl-2-piperazino-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Added to 20 mℓ of AcOH were 1.5 g (4.45 mmol, Referential Example 44) of 6-ethyl-2-(4-benzylpiperazino)-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d] pyrimidine and 0.15 g of 10% Pd-C. While bubbling H₂ at 80°C, the reaction was conducted for 1 hour. After completion of the reaction, Pd-C was filtered off, AcOH was distilled off under reduced pressure, the residue was dissolved in chloroform, and the chloroform solution was neutralized with a 10% aqueous NaHCO₃ solution. Thereafter, the organic layer was dried with anhydrous MgSO₄, the solvent was distilled off, and the residue was purified by silica gel column chromatography [yield: 0.50 g (45%)]. Melting point: 58.5°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.24 (3H,t,J=7Hz), 2.12 (1H,br.s), 2.95 (4H,br.s), 3.62 (2H,q,J=7Hz), 3.92 (4H,br.s), 4.21 (2H,s), 8.66 (1H,s). Infrared absorption spectrum (KBr tablet, cm⁻¹): 3480, 3300, 2900, 1650, 1618, 1520, 1438, 1236, 1160, 862. Each of the following four compounds was also obtained in a similar manner. 6-Methyl-2-piperazino-5-oxo-5,6-dihydro(7H)pyrrolo(3,4-d]pyrimidine Yield: about 100%. Melting point: 176 - 177°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.98 (4H,m), 3.18 (3H,s), 3.96 (4H,m), 4.24 (2H,s), 8.70 (1H,s). Infrared absorption spectrum (CHCℓ₃, cm⁻¹): 1685, 1618, 1522, 1350. 6-Isopropyl-2-piperazino-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Yield: 96% Melting point: 161 - 162°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.28 (6H,d,J=7Hz), 2.96 (4H,m), 3.94 (4H,m), 4.18 (2H,s), 4.65 (1H,sept.,J=7Hz), 8.70 (1H,s). Infrared absorption spectrum (CHCℓ₃, cm⁻¹): 1680, 1618, 1520, 1345. 6-n-Propyl-2-piperazino-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Yield: about 100%. Melting point: 133 - 137°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 0.96 (3H,t,J=7Hz), 1.66 (2H,hextet,J=7Hz), 1.83 (1H,s), 2.96 (4H,m), 3.53 (2H,t,J=7Hz), 3.93 (4H,m), 4.22 (2H,s), 8.70 (1H,s). Infrared absorption spectrum (CHCℓ₃, cm⁻¹): 3400, 3340, 3000, 2970, 1680, 1610, 1570, 1520, 1345, 1260. 6-n-Butyl-2-piperazino-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Yield: about 100%. Melting point: 108 - 112°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 0.95 (3H,t,J=7Hz), 1.65 (2H,hextet,J=7Hz), 2.52 (4H,m), 3.52 (2H,t,J=7Hz), 3.58 (2H,s), 3.96 (4H,m), 4.21 (2H,s), 7.37 (5H,s), 8.68 (1H,s). Infrared absorption spectrum (CHCℓ₃ , cm⁻¹): 3430, 3340, 3000, 2960, 2930, 1680, 1610, 1575, 1520, 1455, 1435, 1350. Referential Example 46 : 2-Dimethylaminomethylenecyclohexane-1,3-dione While stirring 5.60 g (50 mmol) of cyclohexane-1,3-dione under ice-cooling, 11.9 g (100 mmol) of N,N-dimethylformamidodimethylacetal was added dropwise. They were reacted at 25°C for further 7 hours. Low b.p. fractions were distilled off under reduced pressure from the reaction mixture. The residue was recrystallized from ethyl acetate-hexane to obtain 7.7 g of the intended product as yellowish crystals (yield: 92%). Melting point: 106 - 107°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.92 (2H,m), 2.47 (4H,m), 3.18 (3H,s), 3.40 (3H,s), 8.05 (1H,s). Referential Example 47 : 2-(4-Benzylpiperazino)-5-oxo-5,6,7,8-tetrahydroquinazoline To an ethanol suspension (60 mℓ) of 10.73 g (40 mmol) of 1-amidino-4-benzylpiperazine sulfate, were added an ethanol solution (80 mℓ) of 1.6 g (40 mmol) of sodium hydroxide and then 6.69 g (40 mmol) of the 2-dimethylaminomethylenecyclohexane-1,3-dione obtained in Referential Example 46. The resultant mixture was heated under reflux for 4 hours. After cooling the reaction mixture to room temperature, the solvent was distilled off. The residue was added with 100 mℓ of water and then extracted twice with 200 mℓ of ethyl acetate. The ethyl acetate layer was washed with saturated saline and then dried with anhydrous magnesium sulfate. Ethyl acetate was the distilled off under reduced pressure. The residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane = 3/7) to obtain 9.90 g of the intended product as light yellowish crystals (yield: 77%). Melting point: 96 - 97°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 1665, 1590, 1530, 1515. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.08 (2H,m), 2.5 (6H,m), 2.80 (2H,m), 3.54 (2H,s), 3.96 (4H,m), 7.32 (5H,s), 8.83 (1H,s). Referential Example 48 : 2-Piperazino-5-oxo-5,6,7,8-tetrahydroquinazoline Dissolved in 30 mℓ of ethanol and 10 mℓ of acetic acid was 0.64 g (2 mmol, Referential Example 47) of 2-(4-benzylpiperazino)-5-oxo-5,6,7,8-tetrahydroquinazoline, followed by an addition of 64 mg of 10% Pd-C. The quinazoline derivative was hydrogenated at 50°C for 1 hour under atmospheric pressure. After cooling the reaction mixture to room temperature, the catalyst was filtered off and the solvent was distilled off from the filtrate under reduced pressure. The residue was recrystallized from ethyl acetate to obtain 0.42 g of the intended product as light yellowish crystals (yield: 90%). Melting point: 161 - 162°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 3400 (broad), 1670, 1600, 1530. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.10 (2H,m), 2.60 (2H,m), 2.84 (2H,m), 3.06 (4H,m), 4.08 (4H,m), 8.85 (1H,s). Referential Example 49 : 2-(4-Benzylpiperazino)-5,6,7,8-tetrahydro-5-hydroxyiminoquinazoline Added to 30 mℓ of methanol were 2.6 g (8.07 mmol, Referential Example 48) of 2-(4-benzylpiperazino)-5-oxo-5,6,7,8-tetrahydroquinazoline and 0.67 g (9.64 mmol) of hydroxylamine hydrochloride. The resultant mixture was heated with stirring at 60°C for 2 hours. The reaction mixture was cooled to 20°C and the resultant precipitate was collected by filtration, thereby obtaining 2.85 g of white solid (yield: 95%). Melting point: over 300°C (decomposed). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.80 (2H,m), 2.40 - 2.90 (8H,m), 3.58 (2H,s), 3.92 (4H,t,J=6Hz), 7.34 (5H,s), 8.91 (1H,s). Infrared absorption spectrum (KBr tablet, cm⁻¹): 3150, 2920, 2444, 1618, 1582, 1510, 1500, 1275, 1032, 955. Referential Example 50 : 2-(4-Benzylpiperazino)-5,6,7,8-tetrahydro-5-(p-toluenesulfonyl)iminoquinazoline Added to a mixture of 30 mℓ of acetone, 2 g (5.35 mmol, Referential Example 49) of 2-(4-benzylpiperazino)-5,6,7,8-tetrahydro-5-hydroxyiminoquinazoline, and 1.6 g (8.4 mmol) of p-toluenesulfonyl chloride was a solution of 0.7 g (11 mmol) of KOH in 10 mℓ of water. The resultant mixture was stirred at 20°C for 4 hours. After completion of the reaction, the reaction mixture was poured in saline and then extracted with ethyl acetate. The organic layer was dried to solid and the residue was purified by silica gel column chromatography (eluent: CHCℓ₃-ethanol), thereby obtaining 1.5 g of white solid (yield: 59%). Melting point: 180.6°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.68 - 1.98 (2H,m), 2.44 (3H,s), 2.46 - 2.85 (8H,m), 3.57 (2H,s), 3.90 (4H,t,J=6Hz), 7.26 - 7.40 (7H,m), 7.86 (1H,s), 7.95 (1H,s), 8.69 (1H,s). Infrared absorption spectrum (KBr tablet, cm⁻¹): 2920, 1578, 1526, 1424, 1188, 1176, 1005, 992. Referential Example 51 : 2-(4-Benzylpiperazino)-6-oxo-6,7,8,9-tetrahydro(5H)pyrimido[5,4-b]azepine Dissolved in 30 mℓ of acetic acid was 1.3 g (4 mmol, Referential Example 50) of 2-(4-benzylpiperazino)-5,6,7,8-tetrahydro-5-(p-toluenesulfonyl)iminoquinazoline). The resultant mixture was heated at 100°C for 4 hours. After completion of the reaction, acetic acid was distilled off. The residue was dissolved in CHCℓ₃. After neutralizing and washing the thus-obtained chloroform solution with a 10% aqueous NaHCO₃ solution, the solvents were distilled off and the residue was recrystallized from toluene to obtain 0.70 g of white solid (yield: 97%). Melting point: 210.7°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.26 - 2.40 (4H,m), 2.49 (4H,t,J=6Hz), 2.83 (2H,t,J=7Hz), 3.55 (2H,s), 3.82 (4H,t,J=6Hz), 7.32 (5H,s), 7.83 (1H,s), 7.94 (1H,s). Infrared absorption spectrum (KBr tablet, cm⁻¹): 3150, 2900, 2830, 1660, 1595, 1346, 1010, 982. Referential Example 52 : 5-Ethyl-2-(4-benzylpiperazino)-6-oxo-6,7,8,9-tetrahydro(5H)pyrimido[5,4-b]azepine Added to 30 mℓ of THF were 0.65 9 (1.84 mmol, Referential Example 51) of 2-(4-benzylpiperazino)-6-oxo-6,7,8,9-tetrahydro(5H)pyrimido[5,4-b]azepine and 0.15 g (3.75 mmol) of 60% NaH. The resultant mixture was stirred at 20°C for 30 minutes. Thereafter, 3 g (27.8 mmol) of ethyl bromide was added and the reaction mixture was heated to 60°C at which the reaction was conducted for 5 hours. After completion of the reaction, the solvent was distilled off and the residue was purified by silica gel column chromatography to obtain 0.65 g of a colorless oil (yield: 92%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.15 (3H,t,J=7Hz), 2.16 - 2.38 (4H,m), 2.53 (4H,t,J=6Hz), 2.74 (2H,t,J=5.5Hz), 2.58 (2H,s), 3.80 (2H,q,J=7Hz), 3.87 (4H,t,J=6Hz), 7.35 (5H,s), 8.13 (1H,s). Infrared absorption spectrum (KBr tablet, cm⁻¹): 2920, 1657, 1589, 1444, 1250, 1000, 980. Referential Example 53 : 5-Ethyl-2-piperazino-6-oxo-6,7,8,9-tetrahydro(5H))pyrimido[5,4-b]azepine To a mixed solvent of 30 mℓ of acetic acid and 10 mℓ of ethanol, 0.6 g (2.18 mmol, Referential Example 52) of 5-ethyl-2-(4-benzylpiperazino)-6-oxo-6,7,8,9-tetrahydro(5H)pyrimido[5,4-b]azepine and 0.06 g of 10% Pd-C were added. While causing hydrogen gas to flow through the reaction mixture, the reaction was allowed to proceed at 100°C for 4 hours. Thereafter, the Pd/C was filtered off and the filtrate was dried to obtain 0.5 g of a light yellowish oily substance (yield: about 100%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.16 (3H,t,J=7Hz), 2.21 - 2.40 (4H,m), 2.75 (2H,t,J=5.5Hz), 2.96 (4H,t,J=6Hz), 3.70 - 4.05 (6H,m), 8.15 (1H,s). Infrared absorption spectrum (neat, cm⁻¹): 3460, 3300, 2940, 1650, 1595, 1445, 1128, 984. Similarly, the following compound was also obtained by the following procedure. 2-Piperazino-6-oxo-6,7,8,9-tetrahydro(5H)pyrimido[5,4-b]azepine Added to 20 mℓ of ethanol were 0.1 g (0.3 mmol, Referential Example 51) of 2-(4-benzylpiperazino)-6-oxo-6,7,8,9-tetrahydro(5H)pyrimido[5,4-b]azepine and 0.01 g of 10% Pd-C. In a hydrogen atmosphere, they were reacted at 50°C for 4 hours. After filtering off the Pd-C, the filtrate was dried to solid to obtain 0.074 g of colorless crystals in a quantitative yield. Melting point: 175 - 178°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.2-2.5 (4H,m), 2.7-3.0 (2H,m), 2,94 (4H,t,J=4.5Hz), 3.81 (4H,t,J=4.5Hz), 7.00 (1H,br.s), 7.98 (1H,s). Infrared absorption spectrum (nujol, cm⁻¹): 1685, 1600, 1505, 1350, 1255. Referential Example 54 2-(4-Benzylpiperazino)-5,6-dihydro-7-ethyl-6-oxo(7H)pyrrolo[2,3-d]pyrimidine A mixture of 1.41 g (3.76 mmol, Referential Example 71) of ethyl 2-(4-benzylpiperazino)-4-chloropyrimidine-5-acetate, 5 mℓ of ethylamine and 20 mℓ of isopropanol was placed in a pressure vessel, in which they were heated at 120°C for 2 hours. The solvent was then driven off under reduced pressure. The residue was added with water, followed by extraction with chloroform. After drying the organic layer with MgSO₄, it was concentrated. The residue was purified by silica gel column chromatography to obtain 0.58 of the above-identified compound (yield: 46%). Melting point: 110 - 113°C. Infrared absorption spectrum (CDCℓ₃ solution, cm⁻¹): 1725, 1620, 1570. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.25 (3H,t,J=7.0Hz), 2.49 (4H,t,J=5.2Hz), 3.37 (2H,s), 3.54 (2H,s), 3.75 (2H,q,J=7.2Hz), 3.83 (4H,t,J=5.2Hz), 7.31 (5H,s), 7.89 (1H,s). Similarly, the following two compounds were also obtained. 2-(4-Benzylpiperazino)-5,6-dihydro-7-methyl-6-oxo(7H)pyrrolo[2,3-d]pyrimidine Yield: 72%. Melting point: 172 - 174°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.50 (4H,m), 3.18 (3H,s), 3.40 (2H,s), 3.54 (2H,s), 3.84 (4H,m), 7.34 (5H,m), 7.90 (1H,s). Infrared absorption spectrum (KBr tablet, cm⁻¹): 1735, 1630, 1575, 1520, 1480, 1340, 1245. 2-(4-Benzylpiperazino)-5,6-dihydro-7-isopropyl-6-oxo(7H)pyrrolo[2,3-d]pyrimidine Yield: 36%. Melting point: 125 - 127°C. ¹N-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.48 (6H,d,J=7Hz), 2.50 (4H,m), 3.36 (2H,s), 3.56 (2H,s), 3.82 (4H,m), 4.62 (1H,sept.,J=7Hz), 7.33 (5H,m), 7.89 (1H,s). Infrared absorption spectrum (KBr tablet, cm⁻¹): 1730, 1620, 1580, 1440, 1220, 1100. Referential Example 55 : 5,6-Dihydro-7-ethyl-6-oxo-2-piperazino(7H)pyrrolo[2,3-d]pyrimidine Using as a solvent 15 mℓ of ethanol which contained 0.12 mℓ of formic acid, 0.54 g (1.60 mmol, Referential Example 54) of 2-(4-benzylpiperazino)-5,6-dihydro-7-ethyl-6-oxo(7H)pyrrolo[2,3-d]pyrimidine was hydrogenated at normal pressure in the presence of 0.1 g of 10% Pd-C. After being refluxed for 4.5 hours, the catalyst was filtered off and ethanol was distilled off under reduced pressure. The residue was added with an aqueous solution of sodium carbonate, followed by extraction with chloroform. The organic layer was dried with MgSO₄ and then concentrated, thereby obtaining 0.36 g of the above-identified compound as an oily product (yield: 91%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.27 (3H,t,J=7.0Hz), 2.02 (1H,br.s), 2.92 (4H,t,J=5.2Hz), 3.40 (2H,s), 3.80 (6H,m), 7.91 (1H,s). The following compounds were also obtained in a similar manner. 5,6-Dihydro-7-methyl-6-oxo-2-piperazino(7H)pyrrolo[2,3-d]pyrimidine Yield: 70%. Melting point: 145 - 147°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.86 (1H,br.s), 2.94 (4H,m), 3.21 (3H,s), 3.43 (2H,s), 3.82 (4H,m), 7.93 (1H,s). Infrared absorption spectrum (KBr tablet, cm⁻¹): 3340, 1738, 1630, 1580, 1450, 1105. 5,6-Dihydro-7-isopropyl-6-oxo-2-piperazino(7H)pyrrolo[2,3-d]pyrimidine Yield: 83%. Melting point: 113 - 115°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.52 (6H;d,J=7Hz), 2.08 (1H, br.s), 2.93 (4H,m), 3.40 (2H,s), 3.80 (4H,m), 4.65 (1H,sept.,J=7Hz), 7.47 (1H,s), 7.93 (1H,s). Infrared absorption spectrum (neat, cm⁻¹): 3330, 1725, 1622, 1575, 1440, 1220, 1110. Referential Example 56 : 8-Ethyl-5-oxo-2-piperazino-5,6,7,8-tetrahydropyrido[2,3-d]pyrimidine A mixture, which consisted of 2.5 g (11.3 mmol) of 8-ethyl-5-oxo-2-methylthio-5,6,7,8-tetrahydropyrido[2,3-d]pyrimidine (synthesized by the process described in Japanese Patent Laid-Open No. 18600/1978), 2.93 g (34.0 mmol) of anhydrous piperazine and 20 mℓ of dimethylsulfoxide, was heated at 120°C for 3.5 hours and then at 140°C for 6.5 hours. Dimethylsulfoxide was distilled off under reduced pressure. The residue was added with water, followed by extraction with chloroform. The organic layer was dried with MgSO₄ and then concentrated to obtain 3.08 g of the above-identified compound as an oily product (yield: 90%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.20 (3H,t,J=7.2Hz), 1.77 (1H,s), 2.61 (2H,dd,J=6.6,6.7Hz), 2.90 (4H,m), 3.59 (4H,m), 3.88 (4H,m), 8.59 (1H,s). Referential Example 57 : 6,9-Dimethyl-2-methylthio-5-oxo-5,6,7,8-tetrahydro(9H)pyrimido[4,5-e]diazepine To a mixture of 4.58 mℓ (43.0 mmol) of N,N'-dimethylethylenediamine [synthesized by the process described in J. Am. Chem. Soc., 65, 350(1943)], 150 mℓ of EtOH and 2.51 g of Na₂CO₃, an ethanol solution (50 mℓ) of 5.0 g (21.5 mmol) of ethyl 4-chloro-2-methylthiopyrimidine-5-carboxylate was added dropwise over 50 minutes. After being refluxed for 13 hours, ethanol was distilled off under reduced pressure. The residue was added with water, followed by extraction with chloroform. The organic layer was dried and then concentrated. The residue was purified by silica gel column chromatography to obtain 3.55 g of the above-identified compound (yield: 69%). Melting point: 153 - 155°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.52 (3H,s), 3.13 (3H,s), 3.23 (3H,s), 3.63 (4H,ABqualt.), 8.72 (1H,s). Referential Example 58 : 6,9-Dimethyl-2-(4-benzylpiperazino)-5-oxo-5,6,7,8-tetrahydro(9H)pyrimido[4,5-e]diazepine Continuously stirred at 140 - 170°C for 28 hours were 1.3 g (5.46 mmol) of 6,9-dimethyl-2-methylthio-5-oxo-5,6,7,8-tetrahydro(9H)pyrimido[4,5-e]diazepine and 4 g (22.69 mmol) of 1-benzylpiperazine. After cooling the reaction mixture, ethyl acetate was added to the reaction mixture and insoluble matter was filtered off. Then, the ethyl acetate solution was concentrated and the residue was purified by column chromatography to obtain 0.2 g of the intended product as reddish brown oil (yield: 10%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.47 (4H,m), 3.11 (3H,s), 3.12 (3H,s), 3.55 (6H,m), 3.84 (4H,m), 7.32 (5H,m), 8.72 (1H,s). Referential Example 59 : 6,9-Dimethyl-2-piperazino-5-oxo-5,6,7,8-tetrahydro(9H)pyrimido[4,5-e]diazepine Dissolved in 10 mℓ of ethanol was 0.2 g (0.55 mmol) of 6,9-dimethyl-2-(4-benzylpiperazino)-5-oxo-5,6,7,8-tetrahydro(9H)pyrimido[4,5-e]diazepine, followed by an addition of 20 mg of 10% Pd-C. Under reflux, the reactant was hydrogenated at atmospheric pressure for 2 hours. After cooling the reaction mixture to room temperature, the catalyst was filtered off and the filtrate was concentrated under reduced pressure. The residue was purified by column chromatography to obtain 0.1 g of the intended product (yield: 67%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 3.59 (6H,s), 3.27 (4H,m), 3.62 (4H,br.s), 4.20 (4H,m), 8.70 (1H,s). Referential Example 60 : Ethyl 4-amino-2-(4-benzylpiperazino)pyrimidine-5-carboxylate and 2-(4-benzylpiperazino)-5-cyano-4-hydroxypyrimidine Mixed were 26.8 g of 1-amidino-4-benzylpiperazine sulfate and 133 mℓ of a 3% ethanol solution of sodium hydroxide, followed by an addition of 17.0 g of ethyl 2-cyano-3-ethoxyacrylate. After being refluxed for 5 hours, the reaction mixture was allowed to cool down. After distilling off ethanol from the reaction mixture, the residue was added with water and ethyl acetate. The resultant mixture was shaken. Precipitated colorless crystals of 2-(4-benzylpiperazino)-5-cyano-4-hydroxypyrimidine were collected by filtration, washed with water and then dried, thereby obtaining 7.4 g of 2-(4-benzylpiperazino)-5-cyano-4-hydroxypyrimidine (yield: 25%). Melting point: 243 - 244°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.45 (4H,m), 3.45 (2H,m), 3.50 (2H,s), 3.73 (2H,m), 7.32 (5H,m), 8.12 (1H,s). The filtrate was shaken, and the organic layer was dried and concentrated to obtain solid matter. The solid matter was added with ether. After removing insoluble matter, ether was distilled off to obtain 11.2 g of ethyl 4-amino-2-(4-benzylpiperazino)pyrimidine-5-carboxylate as light yellowish crystals. Melting point: 224 - 245°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.34 (3H,t,J=7Hz), 2.46 (4H,m), 3.53 (2H,s), 3.86 (4H,m), 4.27 (2H,q,J=7Hz), 7.32 (5H,m), 8.63 (1H,s). Referential Example 61 : Ethyl 4-acetylamino-2-(4-benzylpiperazino)pyrimidine-5-carboxylate In acetic anhydride, 1.00 g of ethyl 4-amino-2-(4-benzylpiperazino)pyrimidine-5-carboxylate (the compound synthesized in Referential Example 60) was refluxed for 1 hour. After allowing the reaction mixture to cool down, acetic anhydride was distilled off and the resulting viscous oil was purified by silica gel column chromatography to obtain 0.68 g of the above-identified compound (yield: 61%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.36 (3H,t,J=7Hz), 2.48 (3H,s), 2.52 (4H,m), 3.56 (2H,s), 3.92 (4H,m), 4.33 (2H,q,J=7Hz), 7.33 (5H,m), 8.78 (1H,s). Referential Example 62 : Ethyl 2-(4-benzylpiperazino)-4-hydroxypyrimidine-5-carboxylate An ethanol solution of 25.2 g of sodium hydroxide was added with 160 g (0.60 mol) of 1-amidino-4-benzylpiperazine sulfate, followed by a dropwise addition of 129.4 g (0.60 mol) of diethyl ethoxymethylenemalonate over 20 minutes. After being refluxed for 5.5 hours, the reaction mixture was cooled and the precipitated crystals were collected by filtration. The thus-obtained crystals were washed with water and then dried, thereby obtaining 131.4 g of the above-identified compound (yield: 64%). Melting point: 151 - 153°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.36 (3H,t,J=7Hz), 2.49 (4H,m), 3.54 (2H,s), 3.93 (4H,m), 4.35 (2H,q,J=7Hz), 7.31 (5H,s), 8.63 (1H,s). Referential Example 63 : Ethyl 2-(4-benzylpiperazino)-4-chloropyrimidine-5-carboxylate A mixture of 130.0 g (0.38 mol) of ethyl 2-(4-benzylpiperazino)-4-hydroxypyrimidine-5-carboxylate (the compound synthesized in Referential Example 62) and 390 mℓ of thionyl chloride was refluxed for 10 hours. After adding 600 mℓ of toluene, the resultant mixture was distilled to remove excess thionyl chloride. The reaction mixture was ice-cooled and was then added with an aqueous solution of sodium hydroxide to render it alkaline. It was then extracted with chloroform. After drying the chloroform layer with MgSO₄, chloroform was distilled off under reduced pressure to obtain 120.2 g of the above-identified compound as an oily product (yield: 88%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.36 (3H,5,J=7Hz), 2.50 (4H,m), 3.56 (2H,br.s), 3.92 (4H,m), 4.32 (2H,q,J=7Hz), 7.35 (5H,s), 8.79 (1H,s). Referential Example 64 : Ethyl 2-(4-benzylpiperazino)-4-ethylaminopyrimidine-5-carboxylate To a mixture of 101.3 g (0.28 mol) of ethyl 2-(4-benzylpiperazino)-4-chloropyrimidine-5-carboxylate (the compound synthesized in Referential Example 63) and 590 mℓ of chloroform, 72.3 g (1.12 mol) of a 70% aqueous solution of ethylamine was added dropwise over 15 minutes. The resultant mixture was stirred at room temperature for 2 hours. The reaction mixture was added with water, followed by extraction with chloroform. After drying the chloroform layer with MgSO₄, chloroform was distilled off to obtain 103.5 g of the above-identified compound as an oily product (yield: about 100%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.22 (3H,t,J=7Hz), 1.32 (3H,t,J=7Hz), 2.47 (4H,m), 3.46 (2H,d,q,J=5,7Hz), 3.54 (2H,s), 3.88 (4H,m), 4.25 (2H,q,J=7Hz), 7.31 (5H,s), 8.00 (1H,br.t,J=5Hz), 8.58 (1H,s). Each of the following compounds was also prepared in a similar manner. Referential Example 65 : Methyl 2-(4-benzylpiperazino)-4-ethylaminopyrimidine-5-carboxylate To a methanol solution (10 mℓ) containing 0.24 g (4.44 mmol) of sodium methoxide, was added a methanol solution (10 mℓ) of 0.80 g (2.17 mmol) of ethyl 2-(4-benzylpiperazino)-4-ethylaminopyrimidine-5-carboxylate (the compound synthesized in Referential Example 64). The resultant mixture was refluxed for 2 hours. Methanol was distilled off under reduced pressure. Water was added to the residue, followed by extraction with ethyl acetate. The organic layer was dried with MgSO₄ and ethyl acetate was distilled off under reduced pressure, thereby obtaining 0.75 g of the above-identified compound as an oily product (yield: 97%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.22 (3H,t,J=7Hz), 2.48 (4H,m), 3.47 (2H,d,q,J=5,7Hz), 3.54 (2H,s), 3.79 (3H,s), 3.83 (4H,m), 7.31 (5H,s), 7.96 (1H,br.t,J=5Hz), 8.56 (1H,s). The following compounds were also synthesized in a similar manner. Structural formula Referential Example 66 : Methyl 2-(4-benzylpiperazino)-4-methoxypyrimidine-5-carboxylate To a methanol solution (50 mℓ) of 1.88 g (34.8 mmol) of sodium methoxide, a methanol solution (40 mℓ) of 10.1 g (28.0 mmol) of ethyl 2-(4-benzylpiperazino)-4-chloropyrimidine-5-carboxylate (the compound synthesized in Referential Example 63) was added dropwise over 10 minutes. The resultant mixture was stirred at room temperature for 1 hour. Methanol was distilled off under reduced pressure and water was added, followed by extraction with chloroform. After drying the chloroform layer with MgSO₄, chloroform was distilled off under reduced pressure and the residue was recrystallized from methanol-ethyl acetate to obtain 7.9 g of the above-identified compound (yield: 79%). Melting Point: 135 - 138°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.49 (4H,m), 3.54 (2H,s), 3.82 (3H,s), 3.90 (4H,m), 3.97 (3H,s), 7.32 (5H,s), 8.71 (1H,m). Referential Example 67 : 2-(4-Benzylpiperazino)-4-ethylaminopyrimidine-5-carboxylic acid After refluxing for 1 hour a mixture of 106.4 g (0.29 mol) of ethyl 2-(4-benzylpiperazino)-4-ethylaminopyrimidine-5-carboxylate (the compound synthesized in Referential Example 64), 38.0 g (0.58 mol) of a 85% aqueous solution of potassium hydroxide, 100 mℓ of water and 400 mℓ of ethanol, ethanol was distilled off under reduced pressure. The residue was added with water and then neutralized with hydrochloric acid. The precipitated crystals were collected by filtration and were then dried to obtain 80.3 g of the above-identified compound (yield: 82%). Melting point: 158 - 160°C. ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 1.18 (3H,t,J=7Hz), 2.66 (4H,m), 3.44 (2H,d,q,J=5,7Hz), 3.75 (2H,s), 3.91 (4H,m), 7.35 (5H,s), 8.19 (1H,br.t,J=5Hz), 8.45 (1H,s). Each of the following compounds was also synthesized in a similar manner. Referential Example 68 : 2-(4-Benzylpiperazino)-4-ethylaminopyrimidine-5-carboxylic acid diethylamide A mixture of 0.5 g (1.46 mmol) of 2-(4-benzylpiperazino)-4-ethylaminopyrimidine-5-carboxylic acid (the compound synthesized in Referential Example 67) and 20 mℓ of chloroform was added with 0.2 mℓ (1.43 mmol) of triethylamine, followed by a further addition of 0.22 mℓ (3.02 mmol) of thionyl chloride. The resultant mixture was stirred at room temperature for 1 hour. After adding 1.0 mℓ (9.67 mmol) of diethylamine and stirring the resultant mixture for 1 hour, water was added. The resultant mixture was extracted with chloroform. After drying the chloroform layer with MgSO₄, the solvent was distilled off under reduced pressure and the residue was purified by silica gel column chromatography to obtain 0.37 g of the above-identified compound (yield: 64%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.20 (3H,t,J=7Hz), 1.21 (3H,t,J=7Hz), 1.25 (3H,t,J=7Hz), 2.48 (4H,m), 3.45 (6H), 3.54 (2H,s), 3.84 (4H,m), 6.98 (1H,br.t,J=5Hz), 7.32 (5H,s), 7.90 (1H,s). Each of the following compounds was also synthesized in a similar manner. Referential Example 69 : 2-Piperazino-4-ethylaminopyrimidine-5-carboxylic acid diethylamide Using 20 mℓ of ethanol and 0.1 mℓ of 99% formic acid as solvents and 0.1 g of 10% Pd-C as a catalyst, 0.33 g (0.83 mmol) of 2-(4-benzylpiperazino)-4-ethylaminopyrimidine-5-carboxylic acid diethylamide (the compound synthesized in Referential Example 68) was refluxed for 1 hour for its hydrodecomposition. The catalyst was filtered off and the solvents were distilled off under reduced pressure, thereby obtaining 0.26 g of the above-identified compound as an oily product (yield: about 100%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.23 (9H), 3.36 (4H,m), 4.47 (6H), 4.21 (4H,m), 7.05 (1H,br.t,J=5Hz), 7.27 (5H,s), 7.90 (1H,s). Each of the following compounds was also obtained in a similar manner. Referential Example 70 : Ethyl 2-(4-benzylpiperazino)-4-hydroxypyrimidine-5-acetate Added to an ethanol solution of sodium ethoxide, which had been prepared from 0.57 g (24.8 mmol) of sodium and 30 mℓ of EtOH, was 6.61 g (24.7 mmol) of 1-amidino-4-benzylpiperazine sulfate, followed by a dropwise addition of an ethanol solution (10 mℓ) of 5.0 g (24.7 mmol) of ethyl 2-formylsuccinate [the compound described in Ann. 363, 340] over 15 minutes. The resultant mixture was then refluxed for 4.5 hours. After cooling the reaction mixture, crystals were collected by filtration and then washed with water to obtain 3.65 g of the above-identified compound (yield: 41%). Melting point: 203 - 205°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.17 (3H,t,J=7Hz), 2.50 (4H,m), 3.26 (2H,s), 3.54 (2H,s), 3.71 (4H,m), 4.01 (2H,q,J=7Hz), 7.31 (5H,s), 7.66 (1H,s). Referential Example 71 : Ethyl 2-(4-benzylpiperazino)-4-chloropyrimidine-5-acetate A mixture of 3.0 g (8.00 mmol) of ethyl 2-(4-benzylpiperazino)-4-hydroxypyrimidine-5-acetate (the compound synthesized in Referential Example 70) and 50 mℓ of toluene was added with 1.12 mℓ (8.03 mmol) of triethylamine and 0.90 mℓ (9.66 mmol) of phosphorus oxychloride. The resultant mixture was stirred at room temperature for 2 hours and was then refluxed for 1 hour. The mixture was poured in water, followed by extraction with chloroform. The chloroform layer was dried with MgSO₄ and the solvent was distilled off under reduced pressure. The residue was purified by alumina column chromatography to obtain 1.85 g of the above-identified compound as an oily product (yield: 59%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.25 (3H,t,J=7Hz), 2.48 (4H,m), 3.53 (4H,s), 3.81 (4H,m), 4.17 (2H,q.J=7Hz), 7.31 (5H,s), 8.10 (1H,s). Referential Example 72 : 2-(4-Benzylpiperazino)-4-ethylaminopyrimidine-5-acetic acid ethylamide A mixture of 1.41 g (3.76 mmol) of ethyl 2-(4-benzylpiperazino)-4-chloropyrimidine-5-acetate [the compound synthesized in Referential Example 71], 5 mℓ of ethylamine and 20 mℓ of isopropanol was placed in a pressure vessel and was then heated at 120°C for 2 hours. Thereafter, the solvent was driven off under reduced pressure and water was added, followed by extraction with chloroform. The organic layer was dried with MgSO₄ and then concentrated. The residue was purified by silica gel column chromatography, thereby obtaining 0.58 g of the above-identified compound (yield: 40%). Melting point: 103 - 107°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.07 (3H,t,J=7Hz), 1.21 (3H,t,J=7Hz), 2.48 (4H,m), 3.16 (2H,s), 2.20 - 2.50 (4H), 3.54 (2H,s), 7.32 (5H,s), 7.59 (1H,s). Referential Example 73 : 2-Piperazino-6,7-dimethoxyquinazoline Refluxed for 2 hours in isoamyl alcohol (15 mℓ) were 0.63 g of 2-chloro-6,7-dimethoxyquinazoline (synthesized by the method described in Japanese Patent Laid-Open No. 36390/1972) and 0.72 g of anhydrous piperazine. Isoamyl alcohol was thereafter distilled off under reduced pressure, followed by extraction with 2N-NaOH and chloroform. The chloroform layer was washed with saturated saline and then dried with anhydrous magnesium sulfate. Chloroform was distilled off under reduced pressure to obtain 0.7 g of the intended product (yield: 91%). The following compound was also synthesized in a similar manner. Referential Example 74 : 2-Chloro-5-methyl-4-methylthio-5,6,7,8-tetrahydrobenzo[1]thieno[2,3-d]pyrimidine To 2.65 g of 2,4-dichloro-5-methyl-5,6,7,8-tetrahydrobenzo[1]thieno[2,3-d]pyrimidine [synthesized by the process described in M. Robba, P. Touzot and R.M. Riquelme, C.R. Acd. Sci. Ser. C.,276(1), 93(1973)] and 50 mℓ of acetone, a MeOH solution (15 mℓ) of 0.68 g of MeSNa which was prepared on the side was added. The resultant mixture was stirred at room temperature for 1 hour. The solvent was distilled off under reduced pressure, followed by extraction with water and chloroform. The chloroform layer was dried with magnesium sulfate and chloroform was distilled off under reduced pressure. The residue was purified by column chromatography to obtain 0.9 g of the intended product (yield: 31%). Referential Example 75 : 5-Methyl-4-methylthio-2-piperazino-5,6,7,8-tetrahydrobenzo[1]thieno[2,3-d]pyrimidine In methylene chloride, 0.9 g of the 2-chloro-5-methyl-4-methylthio-5,6,7,8-tetrahydrobenzo[1]thieno [2,3-d]pyrimidine obtained in Referential Example 74, 0.35 g of 1-piperazinecarboxyaldehyde and 0.6 g of triethylamine were reacted for 3 hours. The reaction mixture was poured in water, followed by extraction with methylene chloride. The methylene chloride layer was dried with anhydrous magnesium sulfate and was then concentrated under reduced pressure. The residue was added with 10 mℓ of HCℓ-saturated ethanol and the resultant mixture was stirred at 80°C for 2 hours. After concentration of the reaction mixture, the concentrate was extracted with chloroform. The chloroform layer was washed with 2N-NaOH and then with saturated saline. The chloroform layer was dried with anhydrous magnesium sulfate and was then concentrated. The residue was purified by column chromatography to obtain 0.6 g of the intended product (yield: 58%). Referential Example 76 : 2-(4-Benzylpiperazino)-5-ethoxypyrido[4,3-d]pyrimidine Phosphorus oxychloride (5 mℓ) was added to 0.56 g (1.74 mmol) of 2-(4-benzyl-1-piperazino)-5-oxopyrido[4,3-d]pyrimidine. They were reacted at 110°C for 1 hour. The reaction mixture was then added dropwise to a mixture of ice, sodium hydrogencarbonate and chloroform. After decomposition, the oil layer was washed with saturated saline and then dried with sodium sulfate. After distilling off chloroform under reduced pressure, an ethanol solution (50 mℓ) of 1.48 g (21.7 mmol) of sodium ethoxide was added at 0°C. The resultant mixture was heated under reflux for 1 hour. After distilling off ethanol under reduced pressure, water was added, followed by extraction with ethanol. The oil layer was washed with saturated saline and then dried with sodium sulfate. Chloroform was distilled off under reduced pressure to obtain 0.55 g of light yellowish oil (yield: 90%). ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.47 (3H,t,J=8Hz), 2.54 (2H,m), 3.57 (2H,s), 4.00 (2H,m), 4.31 (2H,q.J=8Hz), 6.87 (1H,d,J=7Hz), 7.34 (5H,s), 8.04 (1H,d,J=7Hz), 9.24 (1H,s). Referential Example 77 : 5-Ethoxy-2-piperazinopyrido[4,3-d]pyrimidine In a hydrogen atmosphere, a mixture of 0.5 g (1.43 mmol) of the 2-(4-benzylpiperazino)-5-ethoxypyrido[4,3-d]pyrimidine obtained in Referential Example 76, 0.05 g of 10% Pd-C and 30 mℓ of ethanol was heated under reflux for 5 hours. After cooling, the catalyst was filtered off and washed with ethanol. The solvent was distilled off from the mother liquor. Upon recrystallization from ethyl acetate, 0.3 g of white crystals were obtained (yield: 80%). Melting point: 196 - 198°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 3400, 2860, 2790, 1615, 1575, 1560, 1500, 1425, 1330, 1270, 830. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.30 (3H,t,J=8Hz), 3.35 (2H,m), 4.40 (2H,m), 4.56 (2H,q,J=8Hz), 6.93 (1H,d,J=7Hz), 8.14 (1H,d,J=7Hz), 9.31 (1H,s). Referential Example 78 : 2-(4-Benzylhomopiperazino)-4-methylpyrimidine-5-carboxylic acid Dissolved in 10 mℓ of isoamyl alcohol were 4 g of ethyl 4-methyl-2-methylthiopyrimidine-5-carboxylate [synthesized by the process described in Acta. Chim. Sinia., 23, 145(1957)] and 5.39 g of N-benzylhomopiperazine (synthesized by the process described in Japanese Patent Laid-Open No. 18488/1975). They were reacted for 5 hours while being heated under reflux. Thereafter, isoamyl alcohol and excess N-benzylhomopiperazine were distilled off under reduced pressure. The residue was added with 3.4 g of potassium hydroxide and 40 mℓ of ethanol. While being heated under reflux, they were reacted for 2.5 hours. After cooling the reaction mixture, ethanol was distilled off. The residue was dissolved in water and the resultant aqueous solution was adjusted to pH 3 - 4 with conc. hydrochloric acid. By filtration, 2.70 g of the intended product was obtained as crystals. Yield: 44% (based on 5-ethoxycarbonyl-6-methyl-2-methylthiopyrimidine). Melting point: 77 - 80°C. ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 2.20 (2H,m), 2.60 (3H,s), 3.32 (8H,m), 4.28 (2H,s), 7.46 (5H,s), 8.76 (1H,s). Example 1 : 4-Amino-6,7-dimethoxy-2-(4-(5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidin-2-yl)piperazino)quinazoline and acid addition salts thereof In 600 mℓ of isoamyl alcohol as a solvent, 24.5 g of 4-amino-2-chloro-6,7-dimethoxyquinazoline, 27.8 g of the 5,6-dihydro-6-ethyl-5-oxo-2-piperazinopyrido[4,3-d]pyrimidine and 10.8 g of triethylamine were refluxed for 4 hours. After allowing the reaction mixture to cool down, the precipitated crystals were collected by filtration. The crystals were then recrystallized from a mixed solvent of methanol and dichloromethane to obtain 39.4 g of the intended product (melting point: 255 - 259°C; yield: 83%). ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 1.25 (3H,t,J=7Hz), 3.88 (16H,m), 6.27 (1H,d,J=8Hz), 6.79 (1H,s), 7.12 (2H,br.s), 7.44 (1H,s), 7.72 (1H,d,J=8Hz), 9.08 (1H,s). Dissolved in methanol-chloroform was 33.4 g of the free base obtained in the above preparation process, followed by an addition of equimolar amount of HCℓ in ethanol. Thereafter, excess hydrogen chloride and solvent were distilled off to obtain 36 g of the hydrochloride of the above-identified compound. Melting point: 273 - 275°C. ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 1.22 (3H,t,J=7Hz), 3.84 (3H,s), 4.02 (10H,m), 6.22 (1H,d,J=8Hz), 7.62 (1H,s), 7.67 (1H,d,J=8Hz), 7.68 (1H,s), 8.54 (1H,br.s), 8.90 (1H,br.s), 9.03 (1H,s), 12.42 (1H,br.s). IR spectrum (KBr tablet, cm⁻¹): 1635, 1620, 1590, 1570, 1245. Each of the following acid addition salts was synthesized in a similar manner. Acetate m.p. 255 - 256°C Fumarate m.p. 242 - 244°C Maleate m.p. 242 - 244°C Benzoate m.p. 224 - 226°C Citrate m.p. 222 - 226°C Tartrate m.p. 237 - 241°C Hydrogenbromide m.p. 249 - 252°C Methanesulfonate m.p. >300°C Sulfate m.p. 278 - 280°C Phosphate m.p. 292 - 295°C Example 2 : 4-Amino-6,7-dimethoxy-2-(4-(4-ethylamino-5-methoxycarbonylpyrimidine-2-yl)piperazino)quinazoline hydrochloride In 20 mℓ of n-butanol, 1.1 g of 4-amino-2-chloro-6,7-dimethoxyquinazoline and 1.22 g of the 4-ethylamino-5-methoxycarbonyl-2-piperazinopyrimidine obtained in Referential Example 69 were refluxed for 4 hours. After allowing the reaction mixture to cool down, the precipitated crystals were collected by filtration. The crystals were washed with ethanol and then with ethyl acetate to obtain 1.8 g of the above-identified compound (yield: 78%). Melting point: 269 - 270°C (decomposed). ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 1.2 (3H,t,J=7Hz), 3.78 (3H,s), 3.86 (3H,s), 3.92 (3H,s), 3.97 (8H,m), 7.43 (1H,s), 7.74 (1H,s), 8.54 (1H,s). Examples 3 to 80 : Following the procedure of Example 1 or 2, a variety of compounds of this invention were prepared. Results are summarized in Table 1, in which Preparation Processes A and B correspond to Examples 1 and 2 respectively. In addition, the number of one of the Referential Example is given in parenthesis under each Preparation Process. This number indicates the Referential Example in which the corresponding starting material was prepared. Example 81 ; 4-Amino-6,7,8-trimethoxy-2-(4-(5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidin-2-yl)piperazino)quinazoline hydrochloride In 20 mℓ of isoamyl alcohol as a solvent, 1.04 g of 4-amino-2-chloro-6,7,8-trimethoxyquinazoline (synthesized by the process described in Japanese Patent Laid-Open No. 7180/1971) and 1.0 g of the 5,6-dihydro-6-ethyl-5-oxo-2-piperazinopyrido[4,3-d]pyrimidine obtained in Referential Example 14 were refluxed for 4 hours. After allowing the reaction mixture to cool down, the precipitated crystals were collected by filtration and then washed with methanol to obtain 1.16 g of the above-identified compound (yield; 61%). Melting point: 241 - 242°C. ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 1.23 (3H,t,J=7Hz), 3.96 (17H,m), 6.30 (1H,d,J=8Hz), 7.80 (1H,s), 7.85 (1H,d,J=8Hz), 9.12 (1H,s). Example 82 : 4-Amino-6,7-dimethoxy-2-(4-(5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidin-2-yl)homopiperazino)quinazoline and its hydrochloride In 20 mℓ of isoamyl alcohol as a solvent, were refluxed for 9 hours 0.81 g of 4-amino-2-chloro-6,7-dimethoxyquinazoline, 0.88 g of the 5,6-dihydro-6-ethyl-5-oxo-2-homopiperazinopyrimido[4,3-d]pyrimidine obtained in Referential Example 14 and 0.48 g of tri-n-propylamine. After allowing the reaction mixture to cool down, 0.5 g of sodium hydrogencarbonate and 20 mℓ of water were added. After thoroughly stirring the resultant mixture, the solvent was distilled off. The residue was washed with water and then with hot methanol, thereby obtaining 1.24 g of the intended product (yield: 83%). ¹H-NMR spectrum (CDCℓ₃-DMSO-d₆ solution, δ ppm): 1.34 (3H,t,J=6Hz), 2.15 (2H,br.s), 3.93 (18H,m), 6.30 (1H,d,J=7Hz), 7.20 (1H,s), 7.28 (1H,s), 7.41 (1H,d,J=7Hz), 9.19 (1H,s). The free base (1.24 g) obtained in the above preparation process was dissolved in methanoldichloromethane, followed by an addition of 10 mℓ of HCℓ-saturated ethanol. Thereafter, excess hydrogen chloride and solvent were distilled off to obtain 1.40 g of the hydrochloride of the above-identified compound. Melting point: 236 - 238°C. Referential Example 79 : 2-(4-Benzylpiperazino)-6-cyclohexyl-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Dissolved in 40 mℓ of isoamyl alcohol was 2.0 g (5.34 mmol) of ethyl 2(4-benzylpiperazino)-4-chloromethylpyrimidine-5-carboxylate, followed by an addition of 10.5 g (107 mmol) of cyclohexylamine. The resultant mixture was refluxed for 6 hours. After completion of the reaction, the solvent was distilled off and the residue was washed with ether to obtain 1.32 g of the above-identified compound as crystals (yield: 63%). Melting point: 176 - 178°C. Infrared absorption spectrum (CHCℓ₃ solution, cm⁻¹): 3120, 2850, 2800, 1670, 1610, 1572, 1350, 1005. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.20 - 2.00 (10H), 2.52 (4H,t,J=5Hz), 3.58 (2H,s), 3.96 (4H,t,J=5Hz), 4.18 (2H,s), 7.37 (5H,s), 8.69 (1H,s). The compounds given in Table 2 were also obtained in a similar manner. Referential Example 80 : 6-Cyclohexyl-5-oxo-2-piperazino-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine Dissolved in 30 mℓ of ethanol was 1.2 g (3.07 mmol, Referential Example 79) of 2-(4-benzylpiperazino)-6-cyclohexyl-5-oxo-5,6-dihydro(7H)pyrrolo[3,4-d]pyrimidine, followed by an addition of 0.16 g of 10% Pd-C. The pyrimidine derivative was hydrogenated at 60°C. After completion of the reaction, Pd-C was filtered off and ethanol was distilled off to obtain 0.92 g of the above-identified compound as crystals (yield: about 100%). Melting point: 177 - 180°C. Infrared absorption spectrum (CHCℓ₃ solution, cm⁻¹): 3330, 2920, 2850, 1670, 1610, 1570, 1345, 978. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.20 - 2.00 (10H), 2.94 (4H,t,J=5Hz), 3.92 (4H,t,J=5Hz), 4.19 (2H,s), 8.69 (1H,s). The compounds given in Table 3 were also obtained in a similar manner. Referential Example 81 : 6-(4-Benzylpiperazino)-2-methyl-3-oxo-2,3-dihydro-1H-pyrazolo[3,4-d]pyrimidine Added at room temperature (about 20°C) to an EtOH solution (20 mℓ) of 2.0 g of 2-methylhydrazine was a chloroform solution (12 mℓ) of 5.3 g of the ethyl 2-(4-benzylpiperazino)-4-chloropyrimidine-5-carboxylate synthesized in Referential Example 63. The resultant mixture was stirred for 3 hours. The solvent was distilled off and ethyl acetate was added to the resultant solid. After thoroughly mixing the thus-obtained mixture, 3 g of crystals were collected by filtration (yield: 63%). Melting point: 210 - 212°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 2.55 (4H,m), 3.60 (5H,s), 3.96 (4H,m), 6.98 (1H,br.s), 7.36 (5H,m), 8.72 (1H,s). Referential Example 82 : 6-Piperazino-2-methyl-3-oxo-2,3-dihydro-1H-pyrazolo[3,4-d]pyrimidine A catalytic amount of 10% Pd-C was added to an EtOH solution (30 mℓ) of 3.0 g of 6-benzylpiperazino2-methyl-3-oxo-2,3-dihydro-1H-pyrazolo[3,4-d]pyrimidine. In a hydrogen atmosphere, the resultant mixture was stirred at 60°C for 3 hours. After allowing the reaction mixture to cool down, the catalyst was filtered off and the filtrate was concentrated to obtain 1.8 g of the above-identified compound as yellowish crystals (yield: 88%). Melting point: 272 - 276°C (decomposed). ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 3.20 (4H,m), 3.64 (3H,s), 4.24 (2H,m), 8.70 (1H,s). Infrared absorption spectrum (KBr tablet, cm⁻¹): 3600 - 3300, 1700, 1621, 1565, 1443. Referential Example 83 : Diethyl 2-(4-benzylpiperazino)-4,5-pyrimidinedicarboxylate To absolute ethanol with 0.91 g of sodium dissolved therein, 11.5 g of 1-amidino-4-benzylpiperazine sulfate was added. The resultant mixture was stirred at room temperature for 30 minutes, to which 8.8 g of ethyl ethoxymethyleneoxaloacetate [synthesized by the process described in J. Am. Chem. Soc., 73 , 3684 (1951)] was added. After allowing them to react at room temperature for 2 days, the reaction was caused to proceed further for 1 hour while heating the reaction mixture under reflux. After cooling the reaction mixture to room temperature, ethanol was distilled off under reduced pressure and the residue was dissolved in a mixture of water and ethyl acetate. After separation of the water layer, the ethyl acetate layer was washed with water and then with saturated saline. After drying the ethyl acetate layer with magnesium sulfate, ethyl acetate was distilled off under reduced pressure to obtain 13.7 g of the above-identified compound as light brown crystals (yield: 96%). Melting point: 66°C. Infrared absorption spectrum (nujol, cm⁻¹): 1750, 1715, 1590. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.32 (3H,t,J=7Hz), 1.39 (3H,t,J=7Hz), 2.49 (4H,t,J=5Hz), 3.54 (2H,s), 3.94 (4H,t,J=5Hz), 4.30 (2H,q,J=7Hz), 4.42 (2H,q,J=7Hz), 7.31 (5H,s), 8.85 (1H,s). Referential Example 84 : N,N'-Diethyl-2-(4-benzylpiperazino)-4,5-pyrimidinedicarboxylic acid amide Charged in an autoclave were 1.5 g of the diethyl 2-(4-benzylpiperazino)-4,5-pyrimidinedicarboxylate synthesized in Referential Example 83, 1 mℓ of ethylamine and 20 mℓ of DMF. They were reacted at 150°C for 1 hour. After the reaction, DMF was distilled off and the residue was added with 20 mℓ of hexane and 5 mℓ of ethyl acetate. The resultant light yellowish crystals of the above-identified compound were collected by filtration [yield: 0.8 g (54%)]. Melting point: 201°C. Infrared absorption spectrum (nujol, cm⁻¹): 3290, 1650, 1635, 1585. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.23 (3H,t,J=7Hz), 1.24 (3H,t,J=7Hz), 2.54 (4H,t,J=5Hz), 3.46 (2H,q,J=7Hz), 3.49 (2H,q,J=7Hz), 3.56 (2H,s), 3.89 (4H,t,J=5Hz), 7.32 (5H,s), 7.6 (1H,br.s), 9.16 (1H,s), 9.5 (1H,br.s). Referential Example 85 : Diethyl 2-piperazino-4,5-pyrimidinedicarboxylate The diethyl 2-(4-benzylpiperazino)-4,5-pyrimidinedicarboxylate (1.5 g) synthesized in Referential Example 83 was dissolved in a mixture of 20 mℓ of ethanol and 5 mℓ of acetic acid, followed by an addition of 0.15 g of 10% Pd-C. The resultant mixture was stirred at 70°C for 1 hour in a hydrogen atmosphere. After the reaction, ethanol and acetic acid were distilled off under reduced pressure and the residue was dissolved in dichloromethane. The dichloromethane solution was washed with a saturated aqueous solution of sodium bicarbonate. Dichloromethane was distilled off under reduced pressure to obtain 0.97 g of the above-identified compound as a yellowish oily product (yield: 81%). Infrared absorption spectrum (neat, cm⁻¹): 2980, 1745, 1715, 1590, 1540, 1290, 1250. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.33 (3H,t,J=7Hz), 1.40 (3H,t,J=7Hz), 2.03 (1H, br.s), 2.92 (4H,t,J=5Hz), 4.31 (2H,t,J=7Hz), 4.43 (2H,t,J=7Hz), 8.87 (1H,s). Referential Example 86 : N,N'-Diethyl-2-piperazino-4,5-pyrimidinedicarboxylic acid amide Dissolved in 30 mℓ of ethanol was 0.8 g of the N,N'-diethyl-2-(4-benzylpiperazino)-4,5-pyrimidinedicarboxylic acid amide synthesized in Referential Example 84, followed by an addition of 0.08 g of 10% Pd-C. The resultant mixture was stirred at 60°C for 4 hours in a hydrogen atmosphere. After filtering off the 10% Pd-C, ethanol was distilled off under reduced pressure to obtain the above-identified compound as light yellowish crystals [yield: 0.55 g (89%)]. Melting point: 73°C. Infrared absorption spectrum (KBr tablet, cm⁻¹): 3300, 1640, 1585, 1520, 1450, 1265. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.24 (3H,t,J=7Hz), 1.26 (3H,t,J=7Hz), 1.76 (1H, br.s), 2.94 (4H,t,J=5Hz), 3.42 (2H,dt,J=7Hz,2Hz), 3.49 (2H,dt,J=7Hz,2Hz), 3.86 (4H,t,J=5Hz), 7.6 (1H,br.s), 9.16 (1H,s), 9.5 (1H,br.s). Referential Example 87 : 3,5-Dinitro-2-piperazinopyridine In n-butanol (20 mℓ), 1 g of 2-chloro-3,5-dinitropyridine and 2.1 g of anhydrous piperazine were refluxed for 2 hours. Thereafter, n-butanol was distilled off under reduced pressure, followed by extraction with 2N-NaOH and chloroform. The chloroform layer was washed with saturated saline and then dried with anhydrous magnesium sulfate. Under reduced pressure, chloroform was distilled off to obtain 0.4 g of the intended product (yield: 32%). Example 83 : 4-Amino-6,7-dimethoxy-2-(4-(2-methyl-3-oxo-2,3-dihydro-1H-pyrazolo[3,4-d]pyrimidine-6-yl)piperazino)quinazoline hydrochloride Refluxed for 5 hours in isoamyl alcohol (30 mℓ) were 1.74 g (7.3 mmol) of 4-amino-2-chloro-6,7-dimethoxyquinazoline and 1.60 g (7.3 mmol) of the 6-piperazino-2-methyl-3-oxo-2,3-dihydro-1H-pyrazolo[3,4-d]pyrimidine synthesized in Referential Example 82. After allowing the reaction mixture to cool down, the resultant crystals were collected by filtration and then washed with ethanol. The thus-obtained crude crystals were added with ethanol and refluxed for 2 hours. After allowing the mixture to cool down, crystals were collected by filtration and then dried to obtain 2.90 g of the above-identified compound (yield: 84%). Melting point: 272 - 276°C (decomposed). Infrared absorption spectrum (KBr tablet, cm⁻¹): 3400, 3180, 1655, 1594, 1530, 1495, 1438, 1257, 1112, 985. ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 3.64 (3H,s), 3.90 (3H,s), 3.94 (3H,s), 4.05 (8H,m), 7.64 (1H,s), 7.70 (1H,br.s), 7.82 (1H,s), 8.76 (1H,br.s), 8.82 (1H,s), 8.98 (1H,br.s), 12.50 (1H,br.s). Examples 84 to 93 : Following the procedure of Example 83, the compounds given in Table 4 were obtained by using the piperazinopyrimidine derivatives obtained in their corresponding Referential Examples or the like. Example 94 : 4-Amino-6,7-dimethoxy-2-(4-(2-quinolyl)piperazino)quinazoline hydrochloride Mixed were 0.72 g (2.5 mmol) of 4-amino-6,7-dimethoxy-2-piperazinoquinazoline, 0.63 g (3.9 mmol) of 2-chloroquinoline, 0.43 g (3 mmol) of tri-n-propylamine and 15 mℓ of isoamyl alcohol. The mixture was refluxed for 16 hours. After cooling the reaction mixture, the resultant crystals were collected by filtration, followed by their dissolution in a mixed solvent of 10 mℓ of dichloromethane and 10 mℓ of methanol. To the solution, 2 mℓ of a 20% ethanol solution of hydrochloric acid was added. The solvents were distilled off to obtain 0.90 g of the above-identified compound (yield: 80%). Melting point: 243.5 - 244.5°C. ¹H-NMR spectrum (DMSO-d₆ solution, δ ppm): 3.87 (3H,s), 3.91 (3H,s), 3.7 - 4.1 (8H,br.s), 6.8 - 8.1 (8H,m). Referential Example 88 : 4,5-Dimethoxy-2-nitrobenzaldehyde After reacting 135 g of 3,4-dimethoxybenzaldehyde and 500 mℓ of conc. nitric acid at 10°C for 20 hours, the reaction mixture was poured in 3 ℓ of ice water and the resultant crystals were collected by filtration. The crystals were dissolved in a mixed solvent of 8 ℓ of toluene and 500 mℓ of ethyl acetate. After washing the resultant solution once with a saturated aqueous solution of sodium bicarbonate, three times with water and then once with saturated saline, the solution was concentrated to about 500 mℓ under reduced pressure. The concentrate was cooled to room temperature and the resultant yellowish crystals (77.71 g) were then collected by filtration (yield: 61%). Referential Example 89 : 6,7-Dimethoxy-2-hydroxyquinazoline Dissolved in a mixed solvent of 30 mℓ of dichloromethane and 30 mℓ of methanol were 3.17 g of the 4,5-dimethoxy-2-nitrobenzaldehyde synthesized in Referential Example 88, followed by an addition of 0.16 g of 5% Pd-C. The resultant mixture was stirred for 4 hours in a hydrogen atmosphere. Pd-C was filtered off and the solvent was distilled off under reduced pressure. The residue was dissolved in 30 mℓ of acetic acid, followed by an addition of potassium cyanate. After reacting the contents overnight at room temperature, they were heated and reacted for further 1 hour under reflux. The solvent was distilled off under reduced pressure and the residue was purified by column chromatography (silica gel; eluent: 5:1 mixed solvent of dichlromethane and MeOH), thereby obtaining 1.51 g of the above-identified compound as colorless crystals (yield: 49%). Melting point: 260 - 263°C. Referential Example 90 : 2-Hydroxyquinazoline Following the procedure of Referential Example 89, the above-identified compound was obtained from o-nitrobenzaldehyde. Melting point: 189°C. Referential Example 91 : 2-Chloro-6,7-dimethoxyquinazoline Phosphorus oxychloride (50 mℓ) was added to 5.0 g of the 6,7-dimethoxy-2-hydroxyquinazoline synthesized in Referential Example 89. They were heated and reacted for 8 hours under reflux. After allowing the reaction mixture to cool down, phosphorus oxychloride was distilled off under reduced pressure and the residue was dissolved in dichloromethane. After washing the dichloromethane solution once with a saturated aqueous solution of sodium bicarbonate, once with water and then once with saturated saline, the solution was dried with anhydrous sodium sulfate. The solvent was distilled under reduced pressure and the residue was purified by column chromatography (silica gel; eluent: 50:1 mixed solvent of dichloromethane and methanol), thereby obtaining 2.1 g of the intended product as crystals (yield: 38%). Melting point: 237 - 238°C. Referential Example 92 : 2-Chloroquinazoline Following the procedure of Referential Example 91, the above-identified compound was obtained from 2-hydroxyquinazoline. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 7.72 (1H,m), 7.96 (3H,m), 9.32 (1H,s). Example 95 : 6,7-Dimethoxy-2-(4-(5,6-dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-2-yl)piperazino)quinazoline Tri-n-propylamine (0.43 g) was added to 0.67 g of the 2-chloro-6,7-dimethoxyquinazoline synthesized in Referential Example 91 and 0.78 g of the 6-ethyl-2-piperazinopyrido[4,3-d]pyrimidine-5(6H)-one synthesized in Referential Example 14. Using 5 g of isoamyl alcohol as a solvent, they were heated and reacted for 10 hours under reflux. The resultant crystals were collected by filtration and then washed first with ethyl acetate and then with hexane. They were dried to obtain 1.24 g of the above-identified compound as white crystals (yield: 92%). Melting point: 259 - 262°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.36 (3H,t,J=7Hz), 3.96 (3H,s), 3.97 (2H,q,J=7Hz), 4.02 (3H,s), 4.05 (8H,br.s), 6.32 (1H,d,J=7Hz), 6.93 (1H,s), 6.98 (1H,s), 7.30 (1H,d,J=7Hz), 8.82 (1H,s), 9.28 (1H,s). Example 96 : 2-(4-(5,6-Dihydro-6-ethyl-5-oxopyrido[4,3-d]pyrimidine-2-yl)piperazino)quinazoline In a manner similar to that employed in Example 95, the above-identified compound was obtained from the 2-chloroquinazoline synthesized in Referential Example 95 and the 6-ethyl-2-piperazinopyrido[4,3-d]pyrimidine-5(6H)-one synthesized in Referential Example 14 (yield: 30%). Melting point: 222 - 224°C. ¹H-NMR spectrum (CDCℓ₃ solution, δ ppm): 1.33 (3H,t,J=7Hz), 3.92 (2H,q,J=7Hz), 4.08 (8H,br.s), 6.30 (1H,d,J=7Hz), 7.22 (1H,d,J=7Hz), 7.24 (2H,m), 7.62 (2H,m), 9.0 (1H,s), 9.27 (1H,s). Each of the following Examples, which are directed to preparations, makes use of one of the compounds described in Examples 1 to 96 or one of other pharmaceutical compounds embraced by the general formula [I] as an active component. Example 97 : Tablets containing 0.2 mg of their respective active components were individually prepared in the following manner. The active component, starch and microcrystalline were caused to pass through an 80-mesh sieve to mix them intimately. The thus-obtained powder was added with the polyvinylpyrrolidone solution, followed by granulation. The resultant granules were classified through an 18-mesh sieve. The thus-prepared granules were dried at 50 - 60°C and again classified through an 18-mesh sieve. The granules were then added with the calcium carboxymethylcellulose, magnesium stearate and talc which had in advance been classified through an 80-mesh sieve individually. After mixing them together, the resultant mixture was formed into tablets, each having a weight of 100 mg, by a tableting machine. Example 98 : Tablets containing 1 mg of their respective active components were individually prepared in the following manner. The above components were caused to pass through an 80-mesh sieve, thereby mixing them intimately. The thus-obtained powder was compression-formed to prepare tablets each of which had a weight of 100 mg. Example 99 : Capsules containing 0.5 mg of their respective active components were individually prepared in the following manner. The above components were mixed and then caused to pass through an 80-mesh sieve, thereby mixing them intimately. The thus-obtained powder was filled 100 mg by 100 mg in capsules. Example 100 : Ten parts of ammonium polyacrylate were dissolved in 60 parts of water. On the side, 2 parts of glycerin diglycidylether were dissolved with heating in 10 parts of water. Still on the side, 10 parts of polyethylene glycol (Grade 400), 10 parts of water and 0.1 part of an active component were stirred to dissolve the active component. While stirring the aqueous solution of ammonium polyacrylate, the aqueous solution of glycerin diglycidylether and the aqueous solution, which contained polyethylene glycol and the active component, was added to and mixed with the aqueous solution of ammonium polyacrylate to prepare a drug-containing water-base gel formulation. The gel formulation was then coated on a flexible plastic film to give a coat weight of 0.05 mg per square centimeters in term of the active component. The surface was covered by a release paper web, followed by cutting same into cataplasms, each, of 35 cm² wide. Example 101 : Prepared was a mixed water-base sol formulation of 100 parts of sodium polyacrylate, 100 parts of glycerin, 150 parts of water, 0.2 part of triepoxypropyl isocyanurate, 100 parts of ethanol, 25 parts of isopropyl myristate, 25 parts of propylene glycol and 1 part of an active component. The sol formulation was then coated on the surface of a nonwoven rayon fabric of a composite film, which was composed of the nonwoven rayon fabric and a polyethylene film, to 100 µm thick so that a drug-containing tacky mass layer was formed. The content of the releasing adjuvants (i.e., isopropyl myristate and propylene glycol) in the layer was about 20 wt.%. Thereafter, the tacky mass layer was cross-linked at 25°C for 24 hours. A release film was applied on the surface of the tacky mass layer, followed by cutting same into cataplasms, each, of 35 cm² wide. Example 102 : Mixed at 70°C in a kneader was a composition which consisted of 110 parts of a styrene-isoprene-styrene block copolymer, 90 parts of a terpene resin, 60 parts of olive oil, 0.1 part of ethylene glycol diacrylate and 0.5 part of an active component. From an extruder, the mixture was then extruded and coated at 60°C onto one side of a polyvinyl chloride film of 100 µm thick to a thickness of 100 µm, thereby forming a drug-containing tacky mass layer. Thereafter, the tacky mass layer was exposed to ionizing radiation to give a dose of 10 Mrad. The thus-exposed layer was brought into a contiguous relation with a release film, followed by cutting same into desired sizes to form cataplasms. [Effects of the Present Invention] The present invention has made it clear through zoopery that as mentioned above, the compounds [I] of this invention have extremely strong and long-acting antihypertensive effects and some of the compounds reduce or substantially avoid orthostatic hypotension, which is an undesirable side effect accompanying short-term blood pressure drop, compared with the conventionally-known compounds. The antihypertensive effects of certain compounds of this invention as well as their antihypertensive effects along the passage of time, i.e., their antihypertensive patterns and long-acting properties were investigated on spontaneously hypertensive rats (SHRs). Investigation results are shown in Table 5. Many of the compounds of this invention showed stronger antihypertensive activity, weaker degrees of blood pressure drop upon an elapsed time of 1 hour after the administration of the drugs, and development of milder antihypertensive effects and longer-lasting patterns, all, compared with prazosin employed as Control. Furthermore, the toxicity levels of the compounds of this invention are generally weak. By way of example, their acute toxicity are shown in Table 6. As demonstrated herein, the compounds of this invention are generally believed to serve as drugs which have higher activity and lower toxicity, i.e., higher safety. Hereinafter, biological activities of certain compounds of this invention will be shown in Tests 1 and 2. Test 1 : The antihypertensive effects of the certain compounds of this invention were studied in the following manner. Among male, spontaneously hypertensive rats (SHRs) of 20 weeks of age or older and 350 - 430 g heavy all of which had developed hypertension, those having systolic blood pressures of 180 mmHg or higher were used in groups, each of which was constituted of 3 - 4 of the rats. Blood pressures were measured indirectly in terms of systolic blood pressures at tail arteries by a hemodynamometer (W+W electronic, BP-8005) under no anesthesia before administration of drugs and upon elapsed time of 1, 3, 6 and 24 hours after the administration. Besides, heart rates were also measured simultaneously. The compounds were each dissolved or suspended in a 0.5% methylcellulose solution and then administered orally. Results are shown in Table 5. Test 2 : The acute toxicity of certain compounds of this invention were studied in the following manner. Namely, male ddy-mice of 5 weeks of age and male Wister rats of 8 weeks of age were fasted for 18 hours and used in groups each of which was constituted of 4 - 5 of the mice or rats. The compounds were each dissolved or suspended in a 0.5% methylcellulose solution and administered orally (P.O.). On the fourteenth day after the administration, their toxicity were judged. Results are shown in Table 6. As shown in Table 5, the compounds of this invention exhibited sufficient antihypertensive effects when orally administered at the dosage of 1 mg/Kg. The development of their effects were gradual and their maximum effects were observed 6 hours after their administration or even later. In addition, their effects were observed even 24 hours after their administration. They are thus long-acting compounds. With respect to heart rate, the degrees of its increases were slight. From these results, many of the compounds of this invention are expected to show higher antihypertensive effects, to develop lower degrees of heart rate increases and to be less susceptible of developing orthostatic hypotension due to short-term drop in blood pressure, all, compared with prazosin as Control. These features of the compounds of this invention are believed to make them excellent for the treatment of hypertension of mammals. Moreover, their acute toxicity are weak as shown in Table 6. In view of their amounts to be required to develop their efficacy as drugs, they are considered to be highly safe compounds.

Claims: A quinazoline derivative represented by the following general formula [I] or a pharmacologically acceptable salt thereof: wherein R¹⁰⁰ means a hydrogen atom or methoxy group, R²⁰⁰ and R³⁰⁰ denote individually a hydrogen atom or C₁₋₄ alkoxy group, R⁴⁰⁰ is a hydrogen atom or amino group, ℓ stands for 2 or 3, and Het is represented by any one of the following formulae [II] through [XIX]: wherein, in the formula [II], either a single or double bond is formed between the 3- and 4-positions, R² means a hydrogen atom or a C₁₋₄ alkyl, benzyl, diphenylmethyl, cyano or formyl group, R³ denotes a hydrogen atom or a C₁₋₃ alkoxycarbonyl or phenyl group, R⁴ is a hydrogen atom or a C₁₋₄ alkyl, C₃₋₅ cycloalkyl, hydroxy-substituted C₁₋₂ alkyl, C₁₋₂ alkoxy-substituted C₁₋₂ alkyl, phenyl, benzyl or diphenylmethyl group, and X stands for an oxygen or sulfur atom, in the formula [III], either a single or double bond is formed between the 2- and 3-positions, and R⁵ means a hydrogen atom or a C₁₋₄ alkyl group, in the formula [IV], R⁶ and R⁷ mean individually a hydrogen atom or a C₁₋₄ alkyl group, in the formula [V], R⁸ and R⁹ mean individually a hydrogen atom or a C₁₋₄ alkyl group, in the formula [VI], m stands for 2 or 3, and R¹⁰ means a hydrogen atom or a C₁₋₄ alkyl group, in the formula [VII], n stands for an integer of from 2 to 4, in the formula [VIII], R¹¹ to R¹³ mean individually a hydrogen atom or a C₁₋₄ alkyl group, in the formula [IX], R¹⁴ means a hydrogen atom or a hydroxyl, C₁₋₄ alkyl, -NR³¹R³² in which R³¹ is a hydrogen atom or a C₁₋₄ alkyl group and R³² is a hydrogen atom or a C₁₋₄ alkyl or C₂₋₄ acyl group, C₁₋₂ alkylthio or C₁₋₄ alkoxy group, R¹⁵ denotes a C₂₋₄ acyl, C₁₋₄ alkoxycarbonyl, -CONR³³R³⁴ in which R³³ is a hydrogen atom or a C₁₋₄ alkyl group, R³⁴ is a hydrogen atom or a C₁₋₄ alkyl, phenyl, benzyl or diphenylmethyl, halogen-substituted C₁₋₃ alkyl or C₄₋₇ cycloalkyl group or R³³ and R³⁴ couple together to form a methylene moiety which in turn forms a ring having 4 to 5 carbon atoms together with the associated nitrogen atom, -CONHNR³⁵R³⁶ in which R³⁵ and R³⁶ are individually a C₁₋₄ alkyl group, -CH₂CONHR³⁷ in which R³⁷ is a C₁₋₄ alkyl, or cyano group, in the formula [X], R¹⁶ means a C₁₋₄ alkyl group, in the formula [XI], R¹⁷ and R¹⁸ mean individually a hydrogen atom or a C₁₋₄ alkyl group, in the formula [XII], R¹⁹ through R²¹ means a hydrogen atom or a C₁₋₄ alkoxy group, and R²² denotes -NR³⁸R³⁹ in which R³⁸ and R³⁹ are individually a hydrogen atom or a C₁₋₄ alkyl group, or a hydrogen atom, in formula [XIII], R²³ means a hydrogen atom or a C₁₋₄ alkyl group, and R²⁴ denotes a hydrogen atom or a C₁₋₄ alkylthio group, in the formula [XIV], R²⁵ means a C₅₋₈ alkyl, C₄₋₇ cycloalkyl, hydroxy-substituted C₁₋₂ alkyl group, C₁₋₄ alkoxy-substituted C₁₋₄ alkyl, di (C₁₋₄ alkylamino)-substituted C₁₋₄ alkyl, benzyl, diphenylmethyl, triphenylmethyl or 2-phenylethyl group, in the formula [XV], R²⁶ means a C₁₋₄ alkyl group, in the formula [XVI], R²⁷ and R²⁸ are either the same or different and mean individually a C₁₋₄ alkoxy, hydroxyl or C₁₋₄ alkylamino group, or R²⁷ and R²⁸ couple together to form a C₁₋₄ alkyl-substituted imino group, and in formula [XVIII], R²⁹ and R³⁰ are either the same or different and mean individually a C₁₋₄ alkyl group. A quinazoline derivative according to claim 1 represented by the following general formula [I'] or a pharmacologically acceptable salt thereof: wherein R¹⁰⁰ and ℓ are as defined in claim 1 and Het is represented by any one of the formulae [II] through [XVIII] as defined in claim 1. A quinazoline derivative according to claim 1 represented by the following general formula [I''] or a pharmacologically acceptable salt thereof: Wherein Het is represented by any one of the formulae [XIV] through [XIX] as defined in claim 1. A quinazoline derivative according to claim 1 represented by the following formula [I''') or a pharmacologically acceptable salt thereof: wherein R²⁰⁰ and R³⁰⁰ are as defined in claim 1 and R⁴ denotes a C₁₋₄ alkyl group. A process for preparing a quinazoline derivative of the formula [I] as defined in claim 1, or a pharmacologically acceptable salt thereof; which process comprises: (a) reacting a compound represented by the following formula (1): wherein R¹⁰⁰, R²⁰⁰, R³⁰⁰, and R⁴⁰⁰ are as defined in claim 1 and Q means a readily-removable group, with a compound represented by the following general formula (2): wherein ℓ and Het are as defined in claim 1, and if the pharmacologically acceptable salt is desired, further reacting the reaction product represented by the general formula [I] with the corresponding non-toxic acid; or (b) reacting a compound represented by the following general formula (3): wherein R¹⁰⁰, R²⁰⁰, R³⁰⁰, R⁴⁰⁰ and ℓ are as defined in claim 1, with a compound represented by the following general formula (4): Q-Het wherein Het is as defined in claim 1 and Q means a readily-removable group, and if the pharmacologically acceptable salt is desired, further reacting the reaction product represented by the general formula [I] with the corresponding non-toxic acid. An antihypertensive preparation comprising, as an active component, a quinazoline derivative of the general formula [I] as defined in any one of claims 1 to 4, or a pharmacologically acceptable salt thereof. An antihypertensive preparation according to claim 6 also comprising a pharmaceutically acceptable carrier. An hypertensive preparation according to claim 6 or claim 7 also comprising one or more other active antihypertensive components and/or diuretics. The compound as claimed in any one of claims 1 to 4 for use in the treatment of hypertension or heart failure. Use of the compound as claimed in any one of claims 1 to 4 for the manufacture of a medicament for treating hypertension or heart failure.

Inventors: AWAYA, AKIRA, KATO, KOJI, KITAHARA, TAKUMI, KUMAKURA, MIKIO, NAKANO, TAKUO, NISHINA, TAKASHI, OHNO, HIROYASU, SARUTA, SAKAE, WATANABE, KAZUYUKI, YOKOYAMA, KEIICHI
Applicants: MITSUI PETROCHEMICAL INDUSTRIES, LTD., MITSUI PHARMACEUTICAL CO., LTD.
Application year: 1985
Main classification: C07D471
IPC codes: C07D471, C07D401, C07D239, C07D495, C07D487