1,4-DIHYDROPYRIDINE DERIVATIVE

Abstract: A 1,4-dihydropyridine derivative having the formula (I): wherein R₁ represents 2-(5,6-dihydro-p-dioxinyl) group, R₂ represents a pyridyl group which may be substituted with one methyl group or ethyl group, and n is an integer of 1 to 4.

Description: The present invention relates to novel 1,4-dihydropyridine derivatives having pharmacological activity, more particularly to 1,4-dihydropyridine derivatives useful in the therapy for tumors. Many 1,4-dihydropyridine derivatives are already known, and among these a large number are known to have pharmacological activities. Most, however, have pharmacological activities relating to circulatory systems, and there are few reports of other pharmacological activities of an antiinflammatory or liver protection nature. U.S. Patent 4293700 discloses that a 1,4-dihydropyridine compound having no substituents at the 4-position has a metastasis inhibitory effect on some tumors. U.S. Patent 4690935 discloses antitumor and anti-tumor metastasis agents comprising 1,4-dihydropyridine, such as nifedipine or nimodipine, as the active ingredient. EP-A-221382 discloses a method of treating malignant tumors by using a combination of a platinum coordination compound and a compound such as nifedipine or nimodipine, and EP-A-0270926 discloses that compounds having condensed heterocyles with a special structure bonded to the 4-position of 1,4-dihydropyridine potentiate a sensitivity of multi-drug resistant tumor cells. Japanese Unexamined Patent Publication (Kokai) Nos. 64-31780 and 64-31781 disclose that the compounds represented by the below-mentioned formula (I), wherein R₂ is replaced by an alkyloxy group and n is an integer of 2 to 4, remarkably increase the sensitivity of tumor cells having an acquired resistance. The inventions disclosed in above U.S. Patent 4690935 and EP-A-221382 use calcium channel blockers as antitumor drugs or use platinum coordination compounds in combination with antitumor drugs, and have a drawback in that the side effects thereof sometimes limit their practical use. More specifically, the calcium channel blockers used in the above prior art all have a potent hypotensive action (blood pressure lowering action), and are drugs capable of revealing actions for the cardio-vascular system, even in small amount, and therefore have a drawback in that the effect of inconvenient actions on the cardio-vascular system, such as marked hypotension, cannot be avoided when they are used in the large amounts necessary for antitumor action. When the compound disclosed in EP-A-0270926, was administered intraperitoneally to mice, it was found that 3 of 5 mice died at 288 mg/kg (CANCER RESEARCH 49. 1722-1726, April 1, 1989), and thus it must be regarded as strongly toxic in view of the dose (25 x 2 - 75 x 2 mg/kg/day). Further, many of the compounds disclosed in Japanese Unexamined Patent Publication (Kokai) Nos. 64-31780 and 64-31781 have a calcium channel blocking action and hypotensive action, and are not always satisfactory when combined with antitumor drugs. We have carried out intensive research into the effect of combined use of antitumor drugs and the hypotensive action of 1,4-dihydropyridine derivatives, and found that some compounds markedly increase the sensitivity of tumor cells to antitumor drugs, particularly tumor cells having an acquired resistance, and yet cause little hypotension as a side effect and have a low acute toxicity. In accordance with the present invention, there is provided a 1,4-dihydropyridine derivative having the formula (I): wherein R₂ is a 2- or 3-pyridyl group which may be substituted with one methyl group or ethyl group and n is an integer of 1 to 4, preferably 1 to 3. In the present invention, among the 1,4-dihydropyridine derivatives represented by the above formula (I), one having a particularly conspicuous drug sensitivity potentiating action may be a compound wherein R₂ is a 2-pyridyl, 3-pyridyl, 2-(6-methylpyridyl) or 2-(5-ethylpyridyl) group and n is an integer of 1 to 3. Among the above, specific examples of the most preferable compounds include: Bis[2-(6-methylpyridyl)methyl] 4-(2-(5,6-dihydro-p-dioxinyl)]-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (Compound of Example 2); Bis[3-(3-pyridyl)propyl] 4-[2-(5,6-dihydro-p-dioxinyl)]-2,6-dimethyl-1,4-dihydropyridine-3,5- dicarboxylate (Compound of Example 3); and Bis[2-(5-ethylpyridyl)methyl] 4-[2-(5,6-dihydro-p-dioxinyl)]-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (Compound of Example 5). These compounds having specific substituents have conspicuous drug sensitivity potentiating actions when compared with other compounds, as described hereinafter in test examples, but cause little, if any, hypotension as a side effect, and therefore, are particularly useful compounds as pharmaceuticals. All of the 1,4-dihydropyridine derivatives represented by the above formula (I) can be prepared by utilizing reactions well known in the art and utilized for the preparation of 1,4-dihydropyridines. For example, they can be prepared by allowing 2-formyl-p-dioxene to react with β-aminocrotonic ester and acetoacetic ester in the presence or absence of an organic solvent by heating or by heating under reflux (method A), or by allowing 2-formyl-p-dioxene to react with acetoacetic ester and ammonia water in the presence or absence of an organic solvent by heating, preferably under reflux (method B). The reactions used in these preparation methods are basically the same as the reactions used in the prior art for the preparation of 1,4-dihydropyridine compounds (e.g., the reactions used in the methods described in Japanese Patent Publication (Kokoku) Nos. 46-40625, 56-37225, and Japanese Unexamined Patent Publication (Kokai) No. 60-214786). Accordingly, the 1,4-dihydropyridine derivatives of the present invention can be also prepared by utilizing other known reactions in addition to the above methods. The starting compounds to be used in the above preparation methods are all known compounds, and are readily available or can be easily prepared by those skilled in the art. Namely, acetoacetic ester and β-aminocrotonic ester are both compounds conventionally used as starting materials for the preparation of 1,4-dihydropyridine compounds, and are commercially readily available, or can be readily synthesized. Further, 2-formyl-p-dioxene can be prepared by the method described in M. S. Shostakovskii; Izvest. Akad. Nauk. S. S. S. R. Otdel. Khim. Nauk., 1685, (1961). According to the present invention, the reaction product formed according to the above method, i.e., the 1,4-dihydropyridine derivative represented by the formula (I), can be separated from the reaction mixture and purified in a conventional manner, for example, by extraction with a solvent by chromatography or by crystallization. EXAMPLES Synthesis examples of 1,4-dihydropyridine derivatives according to the present invention and the results of pharmacological tests conducted to confirm the usefulness thereof are described below. Example 1 Synthesis of bis(2-pyridylmethyl) 4-[2-(5,6-dihydro-p-dioxinyl)]-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate A 4.06 g (0.040 mole) amount of 2-formyl-p-dioxene, 16.4 g (0.085 mole) of 2-pyridylmethyl acetoacetate and 6.6 ml of 28% ammonia water were dissolved in 40 ml of isopropyl alcohol and heated under reflux for 20 hours. After cooling, the reaction mixture was concentrated, the residue was dissolved in ethyl acetate, and the impurities were removed by extraction with a small amount of water. The ethyl acetate layer was dried over anhydrous sodium sulfate, the solvent was evaporated, and the residue was crystallized with a solvent mixture of ethyl alcohol and n-hexane to give 6.4 g of crystals. Subsequently, recrystallization from isopropyl alcohol gave 5.48 g (yield 29.3%) of the title substance as white crystals. This substance had the following analytical values. m.p: 157.5 - 160.0°C 3300(NH), 1680(C=0), 1200(C-0) NMR(CDCl s , TMS, PPM) 2.30(6H, s ,2,6-position CH₃) 3.90(4H,s dioxene ring OCH₂CH₂O) 4.68(1H,s, 4-position H) 5.31(4H,s, 2 x COO CH₂ ) 5.85(1H,s, vinyl H) 6.30(1H,b,NH) 7.0-7.8, 8.4-8.7(10H,m, 2 x pyridine ring) Elemental analysis (C₂₅H₂₅N₃O₆) Calculated C,64.79 H,5.44 N,9.07 Found C,64.66 H,5.62 N,8.86 Example 2 Synthesis of bis[2-(6-methylpyridyl)methyl] 4-[2-(5,6-dihydro-o-dioxinyl]-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate A 4.00 g (0.035 mole) amount of 2-formyl-p-dioxene, 16.8 g (0.081 mole) of 2-(6-methylpyridyl)methyl acetoacetate and 15 ml of 28% ammonia water were dissolved in 25 ml of isopropyl alcohol and heated under reflux for 20 hours. After cooling, the reaction mixture was concentrated, the residue was dissolved in ethyl acetate, and the impurities were removed by extraction with a small amount of water. The ethyl acetate layer was dried over anhydrous sodium sulfate, the solvent was evaporated, and the residue was subjected to silica gel column chromatography with ethyl acetate solvent. The crystals obtained were recrystallized from isopropyl alcohol to give 1.70 g (yield 10.0%) of the title substance as white crystals. This substance had the following analytical values. m. p.: 158.0 - 160.0°C 3270(NH),1690(C=0),1260(C-0) NMR(CDCl₃,TMS,PPM) 2.33(6H,s,2,6-position CH₃) 2.53(6H,s,2 x pyridine ring 6-position CH₃) 3.81(4H,s, dioxene ring OCH₂CH₂O) 4.64(1H,s, 4-position H) 5.23(4H,ABq,2 x COO CH₂ ) 5.83(1H,s,vinyl H) 5.86(1H,b,NH) 7.02(2H,d,2 x pyridine ring 5-position H) 7.08(2H,d,2 x pyridine ring 3-position H) 7.45(2H,t,2 x pyridine ring 4-position H) Example 3 Synthesis of bis[3-(3-pyridyl)propyl] 4-[2-(5,6-dihydro-p-dioxinyl)]-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate A 4.00 g (0.035 mole) amount of 2-formyl-p-dioxene, 17.9 g (0.081 mole) of 3-(3-pyridyl)propyl acetoacetate and 15 ml of 28% ammonia water were dissolved in 25 ml of isopropyl alcohol and heated under reflux for 20 hours. After cooling, the reaction mixture was concentrated, the residue was dissolved in ethyl acetate, and the impurities were removed by extraction with a small amount of water. The ethyl acetate layer was dried over anhydrous sodium sulfate, the solvent was evaporated, and the residue was subjected to silica gel column chromatography with a solvent mixture of chloroform and methanol. The crystals obtained were washed with ether to give 2.40 g (yield 13.2%) of the title substance as pale yellow crystals. This substance had the following analytical values. m.p.: 113.5 - 115.0°C 3250(NH),1680(C=0),1260(C-0) NMR(CDCl₃,TMS,PPM) 1.79-2.18(4H,m,2 x COOCH₂ CH₂ CH₂) 2.32(6H,s,2,6-position CH₃) 2.74(4H,t,2 x COOCH₂CH₂ CH₂ ) 3.92(4H,s, dioxene ring OCH₂CH₂O) 3.93-4.41(4H,m,2 x COO CH₂ CH₂CH₂) 4.52(1H,s,4-position H) 5.87(1H,s,vinyl H) 5.96(1H,b,NH) 7.03-7.27(2H,m,2 x pyridine ring 5-position H) 7.35-7.56(2H,m,2 x pyridine ring 4-position H) 8.26-8.51(4H,m,2 x pyridine ring 2, 6-position H) Example 4 Synthesis of bis[2-(2-pyridyl)ethyl] 4-[2-(5,6-dihydro-p-dioxinyl)]-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate A 4.00 g (0.035 mole) amount of 2-formyl-p-dioxene 17.0 g (0.082 mole) of 2-(2-pyridyl)ethyl acetoacetate and 15 ml of 28% ammonia water were dissolved in 100 ml of isopropyl alcohol and heated under reflux for 48 hours. After cooling, the reaction mixture was concentrated, the residue was dissolved in ethyl acetate, and the impurities were removed by extraction with a small amount of water. The ethyl acetate layer was dried over anhydrous sodium sulfate, the solvent was evaporated, and the residue was subjected to silica gel column chromatography with a solvent mixture of ethyl acetate and acetone. The crystals obtained were recrystallized from isopropyl alcohol to give 4.34 g (yield 25.2%) of the title substance as pale yellow crystals. This substance had the following analytical values. m.p.: 130.0-131.0°C 3340(NH),1690(C=0),1210(C-0) NMR(CDCl₃,TMS,PPM) 2.20(6H,s,2,6-position CH₃) 3.13(4H,t,2 x COOCH₂ CH₂ ) 3.83(4H,s,dioxene ring OCH₂CH₂O) 4.31(1H,s,4-position H) 4.31-4.69(4H,m,2 x COO CH₂ CH₂) 5.54(1H,s,vinyl H) 5.60(1H,b,NH) 7.00-7.23(4H,m,2 x pyridine ring 3,5-position H) 7.43-7.67(2H,m,2 x pyridine ring 4-position H) 8.48(2H,d,2 x pyridine ring 6-position H) Example 5 Synthesis of bis[2-(5-ethylpyridyl)methyl] 4-[2-(5,6-dihydro-p-dioxinyl)]-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate A 5.00 g (0.044 mole) amount of 2-formyl-p-dioxene, 22.7 g (0.103 mole) of 2-(5-ethylpyridyl) methyl acetoacetate and 10 ml of 28% ammonia water were dissolved in 30 ml of isopropyl alcohol and heated under reflux for 20 hours. After cooling, the reaction mixture was concentrated, the residue was dissolved in ethyl acetate, and the impurities were removed by extraction with a small amount of water. The ethyl acetate layer was dried over anhydrous sodium sulfate, the solvent was evaporated, and the residue was subjected to silica gel column chromatography with a solvent mixture of n-hexane and ethyl acetate. The crystals obtained were recrystallized from isopropyl alcohol and ether to give 4.90 g (yield 22.1%) of the title substance as pale yellow crystals. This substance had the following analytical values. m.p.: 124.0 - 126.0°C 3190(NH),1690(C=0),1260(C-0) NMR(CDCl₃,TMS,PPM) 1.23(6H,t,2 x CH₂ CH₃ ) 2.31(6H,s,2,6-position CH₃) 2.61(4H,q,2 x CH₂ CH₃) 3.89(4H,s, dioxene ring OCH₂CH₂O) 4.62(1H,s,4-position H) 5.24(4H,ABq,2 x COO CH₂ ) 5.86(1H,s, vinyl H) 5.87(1H,b,NH) 7.29-7.51(4H,m,2 x pyridine ring 3,4-position H) 8.32-8.35(2H,m,2 x pyridine ring 6-position H) Example 6 (Test Example) Antitumor agent potentiating effect in vincristine-resistant tumor bearing mouse One million vincristine (VCR)-resistant mouse leukemia (P388/VCR) cells were inoculated intraperitoneally into male 6 to 7-week-old CDF₁ mice. The compounds of this invention and VCR were administered intraperitoneally once a day for 5 consecutive days, the animals were observed, and the survival days for respective animals were determined to obtain the survival ratio (T/C)% relative to the Control. The potentiating effect of the antitumor agent (T/V)% was determined according to the formula shown below. Verapamil was employed as the positive Control compound. The compounds of this invention and the positive Control compound were suspended in a vehicle of 0.5% CMC-Na containing 0.1% Tween 80 and VCR was dissolved in sterilized physiological saline. The results are shown in Tables 1 to 4. In the Tables, Compounds 1 to 5 are those obtained in Examples 1 to 5 respectively. "Tween" is a Registered Trade Mark. Tween 80 is a polyoxyethylene sorbitan monooleate. Example 7 (Test Example) Inhibitory effects on potassium contracture in rat rectum smooth muscle Rat rectum (about 1.5 cm) was isolated and suspended in a Magnus tube. A Locke solution was employed as the nutrient solution, and a contraction of the intestinum rectum was caused by changing the potassium (K) concentration of this solution from 5.6 mmol (mM) to 56.0 mM. This contraction was a contraction through a membrane dependent Ca-channel mediated contraction based on depolarization by a K concentration change. The contraction was recorded by an FD-transducer and polygraph. The compounds of the present invention were permitted to act 5 minutes before changing the K concentration, and simultaneously with changing the K concentration. The compounds of the present invention and the positive Control compound were all dissolved in dimethyl sulfoxide (DMSO) and the concentrations in the-nutrient solution were made 10⁻⁸ and 10⁻⁷ mole (M). A judgement was made 5 minutes after changing the K concentration, and the difference in contraction before the concentration change was indicated as an inhibition % value. Verapamil and nicardipine were employed as the positive control compound . The results are shown in Table 5. In the Table, the respective compounds have the same meanings as described in Example 6. Compound of Invention and positive Control Compound Inhibition ratio (%) 10⁻⁸(M) 10⁻⁷ (M) Compound 1 NT 11.2 Compound 2 -5.6 -2.1 Compound 3 -11.5 -4.2 Compound 4 -6.9 5.2 Verapamil 13.6 50.2 Nicardipine 73.1 NT Note) NT: Not tested Example 8 (Test Example) Hypotensive activity in spontaneously hypertensive rat The systolic blood pressure was measured by using spontaneously hypertensive rats (SHR), which are a model of hypertension when examine the hypotensive activities of the compounds of the present invention and the positive Control compound. The rats were warmed for 5 minutes in a warming box at 55°C, and their blood pressure then measured by a tail cuff plethysmograph. The compounds of the present invention were administered singly and intraperitoneally at a dose of 100 mg/kg and the positive Control compound was administered singly and intraperitoneally at a dose of 10 mg/kg. The compounds of the present invention and the positive Control compound were administered in the same manner as described in Example 6. Blood pressure measurements were taken before administration and 60 minutes after administration. Nicardipine was employed as the positive Control compound. The results are shown in Table 6. In the Table, the respective compounds have the same meanings as described in Example 6. Compound of Invention and Positive Control Compound Dose (mg/kg) Systolic Blood Pressure (mmHg) Blood pressure change kPa(mmHg) Before administration 60 minutes after administration - - 205 218 + 1.73(+ 13) Compound 2 100 219 204 - 2.0 (- 15) Compound 5 100 221 187 - 4.52(- 34) Nicardipine 10 208 86 - 16.2(-122) Example 9 (Test Example) Acute toxicity test Male 6-week-old ICR nice were divided into groups of 2 to 5 mice per group. General signs were observed for 10 days after an intraperitoneal administration of compounds of the present invention, and the mortality rates were determined. The drugs to be tested were administered in varying amounts of 250 to 2000 mg/kg to 5 or 7 groups (a geometrical series of √2), at a dose volume of 10 ml/kg. The results are shown in Table 7. In the Table, the respective compounds have the same meanings as described above. Compound of Invention Dose (mg/kg) 2000 1414 1000 707 500 356 250 Compound 1 0/2 0/2 0/2 - 0/2 - 0/2 Compound 2 0/4 1/5 0/5 0/5 0/5 0/5 0/5 Compound 3 4/4 3/4 1/5 2/5 0/5 0/5 0/5 Compound 5 0/2 0/2 0/3 0/2 0/3 0/3 0/3 The 1,4-dihydropyridine derivative according to the present invention can be used in combination with an antitumor drug to potentiate the effect thereof. This effect is particularly marked for clones having acquired a resistance to the antitumor drug. For example, for a mouse transplanted with P388/VCR cells, which is a vincristine-resistant clone, substantially no life prolonging effect can be obtained by the administration of an antitumor drug alone, but a life prolonging effect can be clearly recognized upon the administration of the compound of the present invention in combination therewith (Table 1 to Table 3), and the mean survival days are clearly prolonged compared with a VCR single administration (potentiating effect 116 to 131%). This life prolonging effect is conspicuous when compared in terms of the life prolonging ratio (T/C %). Also, the compounds of the present invention have a very weak calcium channel blocking activity compared to many other 1,4-dihydropyridine compounds (Table 5), and very little side effects such as hypotension (Table 6). Further, the compounds of the present invention have an extremely low toxicity (Table 7). Therefore, the compounds of the present invention are useful for the therapy of tumors having an acquired resistance.

Claims: Claims for the following Contracting States : BE, CH, DE, FR, GB, IT, LI, NL, SE A 1,4-dihydropyridine derivative having the formula (I): wherein R₂ is a 2- or 3-pyridyl group which may be substituted with one methyl group or ethyl group, and n is an integer of 1 to 4. A 1,4-dihydropyridine derivative as claimed in claim 1, wherein n is an integer of 1 to 3. A 1,4-dihydropyridine derivative as claimed in claim 2, wherein R₂ is 2-pyridyl group, 3-pyridyl group, 2-(6-methylpyridyl) group or 2-(5-ethylpyridyl) group. A 1,4-dihydropyridine derivative as claimed in claim 2, wherein R₂ is 2-(6-methylpyridyl) group and n is 1. A 1,4-dihydropyridine derivative as claimed in claim 2, wherein R₂ is 3-pyridyl group and n is 3. A 1,4-dihydropyridine derivative as claimed in claim 2, wherein R₂ is 2-(5-ethylpyridyl) group and n is 1. Claims for the following Contracting State : ES A method for preparing 1,4-dihydropyridine compound of formula (I) : which comprises allowing 2-formyl-p-dioxene to react with acetoacetic ester (II) and ammonia water with heating CH₃COCH₂ - COO - (CH₂) n - R₂ (II) wherein R₂ is a 2- or 3-pyridyl group which may be substituted with one methyl group or ethyl group and n is an integer of 1 to 4. A method for preparing 1,4-dihydropyridine compound of formula (I) : which comprises allowing 2-formyl-p-dioxene to react with acetoacetic ester (II) and β-aminocrotonic ester (III) with heating CH₃COCH₂ - COO - (CH₂) n - R₂ (II) CH₃C(NH₂) = COO - (CH₂) n - R₂ (III) wherein R₂ is 2- or 3-pyridyl group which may be substituted with one methyl group or ethyl group and n is an integer of 1 to 4. A method as claimed in claim 1 or 2 wherein n is an integer of 1 to 3. A method as claimed in claim 1 wherein R₂ is 2-pyridyl group, 3-pyridyl group, 2-(6-methylpyridyl) group or 2-(5-ethylpyridyl) group. The use of compound of formula I: wherein R₂ is 2- or 3-pyridyl group which may be substituted with one methyl group or ethyl group and n is an integer of 1 to 4 in a method for the preparation of a medicament for potentiating the efficacy of an anti-tumor drug.

Inventors: INADA, HARUAKI, KIUE, AKIRA, SANO, TETSURO, SUZUKI, KENICHI
Applicants: NIKKEN CHEMICALS CO., LTD.
Application year: 1989
Main classification: C07D405
IPC codes: C07D409, C07D405