Platinum complexes and antitumor agents containing them as an active ingredient

Abstract: Novel platinum complexes of the formula: wherein R¹ and R² are identical or different lower alkyl groups, or R¹ and R² taken together form a -(CH₂)m- bridge, and m is an integer from 2 to 5, and antitumor agents comprising the compounds (I) are disclosed, which are effective against cisplatin-resistant ascitic murine leukemia, murine leukemia, and solid tumors with only slight hemotoxicity and nephrotoxicity.

Description: The present invention relates to novel platinum complexes and antitumor agents containing them as an active ingredient. Since platinum complexes were found to have antitumor activity, cisplatin (CDDP, Bristol-Myers Co.), carboplatin (Bristol-Myers Co.), and many kinds of related compounds have been studied. The present inventors have already disclosed glycolate platinum complexes (U.S.Pat.No.4,560,781) and cis-diammineglycolate platinum (U.S.Pat.No.4,575,550), and proved their utility. These achievements were also published in M. Nicolini (ed.) "Platinum and Other Metal Coordination Compounds in Cancer Chemotherapy", 744-748, Boston, Martinus Nijhoff (1988). The object of the present invention is to provide compounds with excellent antitumor activity against CDDP-resistant tumor cells which are effective not only in recurrent cases after recovering remission by CDDP treatment, but also in the treatment of many cases of other malignant tumors. These novel compounds should show only slight marrow suppression and hemotoxicity, so that they may be broadly used either alone or in combination with other drugs without cumulative myelosuppression. In addition, these compounds should show no sign of nephrotoxicity. The present invention thus relates to compounds of the formula: wherein R¹ and R² are identical or different lower alkyl groups, or R¹ and R² taken together form a -(CH₂)m- bridge, and m is an integer from 2 to 5. In the present specification, lower alkyl includes straight-chain C₁-C₄ alkyl groups such as methyl, ethyl, propyl and butyl. Further, R¹ and R² may, taken together, form a -(CH₂)m- bridge and here the alkylene chain may be substituted by halogen atoms such as F, Cl or Br, or lower alkyls such as methyl or ethyl. Since the compounds of this invention show an excellent antitumor activity against CDDP-resistant tumor cells, these compounds are effective not only for the treatment of recurrent cases of remission after CDDP treatment, but also for the treatment of most other malignant tumors. Because the compounds of the invention show only slight marrow suppression and hemotoxicity, they may be broadly used either alone or in combination with other drugs. The compounds of the invention can be prepared according to the following route, using known methods [Wolf, W. et al, J. Pharm. Sci., 65 , 315 (1976) and Totani, T.et al, Chem. Lett., 429 (1986)]. (wherein R¹ and R² have the meaning defined above) The dihydroxy-compound (II), in which two nitrato groups are replaced by hydroxy groups, can be prepared by passing an aqueous solution of the compound (III) through a column filled with an anion exchange resin ( OH- type) such as Diaion SA-10A. The compound (II) is dissociated in aqueous solution as shown below, showing alkalinity. An aqueous solution of the compound (II) is allowed to react with one mol equivalent of the compound (IV), that is, 1-hydroxy-1-cycloalkanecarboxylic acid (IVa) or 2,2-dialkyl-2-hydroxyacetic acid (IVb) to give the desired compound (I). The ion exchange reaction, converting compound (III) into the compound (II) proceeds quantitatively, so that compound (IV) may be used as one mol equivalent to the compound In the synthesis of the objective compound (I), in which R¹ and R² taken together form a cycloalkane ring, the desired cycloalkane ring is previously introduced into the compound (IV) and said compound (IV) is subjected to the next process for preparing the objective compound (I). This reaction is usually carried out at room temperature and terminates within 10 days, but if necessary, the reaction mixture may be heated at 50 to 70°C. The compounds of the present invention (I) are active not only against customary solid tumors but also against cisplatin-resistant mouse leukemia L1210 (L1210/CDDP). Another advantage of the compounds of the invention (I) consists in that they are almost free from marrow suppression or hemotoxicity at a dose high enough to exhibit antitumor action. The compounds of the present invention can be parenterally administered to humans or animals. For example, the compounds of the present invention can be disssolved in an appropriate solvent for injection (e.g. distilled water for injection, physiological saline, 5 % aqueous glucose solution, etc.) and administered intravenously or by way of an intravenous drip. The compounds of the present invention are preferably preserved in ampoules or vials in the form of crystals, powders, fine crystals or lyophilizates, and preferably dissolved into solution immediately before use. Stabilizers may previously be added in this case. It is recommended to administer the compounds of the invention in repeated cycles by administering parenterally 50 to 1500 mg/m² per adult in a single dosage or several divided doses and then withdrawing during 2 to 4 weeks. Presently preferred and practical embodiments of the present invention are illustratively shown in the following examples and experiments, but the present invention will not be limited by them. Example 1 (1R,2R-Diaminocyclohexane)[1-hydroxy-1-cyclopropanecarboxylato(2-)-0¹,O²]platinum (II) (I-1) An aqueous solution of 955 mg (2.20 mmol) of dinitrato (1R,2R-diaminocyclohexane)platinum (III) in 30 ml of water is passed through a column filled with 20 ml of anion exchange resin (Diaion SA-10A, OH⁻ type). To the resulting alkaline effluent, a solution of 235.1 mg (2.23 mmol) of 1-hydroxy-1-cyclopropanecarboxylic acid in 2 ml of water is added, and the mixture is allowed to react at about 60°C for 8 hours. The reaction solution is concentrated under reduced pressure. and the resulting crystals are filtered. The crystals are recrystallized from water to give 641.1 mg (yield; 69.6%) of the objective compound (I-1). mp. 195 °C∼ (decomp.) Anal.Calcd. (%) for C₁₀H₁₈N₂O₃Pt · (H₂O) 0.5 C, 28.71; H, 4.58; N, 6.70; Pt, 46.63 Found (%) C, 28.70; H, 4.60; N, 6.88; Pt, 46.65 IR ν (Nujol): 3400 (b,m), 3180 (b,s), 3100 (b,s), 1630 (s), 1360 (s), 1260 (s), 1180 (m), 1130 (w), 1065 (m), 1030 (m), 990 (m), 905 (w), 830 (m), 740 (m) cm⁻¹ ¹H-NMR (D₂O, external standard TMS δ): 1.42 (m, cyclopropane, 4H), 1.50-2.26, 2.26-3.13 (b, m, cyclohexane, 10H) Example 2 (1R,2R-Diaminocyclohexane)[1-hydroxy-1-cyclopentanecarboxylato(2-)-O¹,O²]platinum (II) (I-2) To an aqueous solution of the dihydroxy compound (II) obtained by treating 1.203 g (2.78 mmol) of the dinitrato compound (III) in the same manner as in Example 1, 363.4 mg (2.79 mmol) of 1-hydroxycyclopentanecarboxylic acid are added, and the mixture is reacted at 60°C for hours. The reaction solution is concentrated to dryness under reduced pressure, and the residue is dissolved in a small amount (5 to 6 ml) of methanol. It is subjected to silica gel column chromatography, and the eluate of Rf=0.60 (methanol) is collected. The resulting component is concentrated and the residue is mixed with acetone, and the resulting crystals are collected. The crystals are washed twice with acetone and dried under reduced pressure to give 876.7 mg (Yield : 72.1 %) of the objective compound (I-2). mp.: 215°C ∼ (decomp.) Anal Calcd. (%) for C₁₂H₂₂N₂O₃Pt: C, 32.95, H, 5.07; N, 6.40; Pt, 44.60 Found (%) C, 32.97; H, 5.20; N, 6.44; Pt, 43.72 IR, ν (Nujol) : 3400 (b,m), 3200 (b,s), 3100 (b,s), 1640 (vs), 1350 (s), 1320 (w), 1305 (w), 1175 (m), 1120 (w), 1070 (m), 1035 (m), 1020 (m), 955 (w), 925 (w), 840 (m) cm⁻¹ ¹H-NMR (D₂O, external standard TMS δ), 1.33-3.02 (b,m cyclopentane+cyclohexane) Example 3 (1,2-Diaminocyclohexane)[1-hydroxy-1-cyclopentanecarboxylato(2-) -O¹,O²]platinum (II) I-3 2.20 g (5.08 mmol) of the dinitrato (III), which was obtained from the starting 1,2-diaminocyclohexane (a mixture of cis and trans isomers, Tokyo Kasei) in a conventional manner, is treated in the same manner as in Example 2 to give 1.634 g (yield: 73.6%) of the objective compound (I-3) (a mixture of cis and trans isomers). mp. 228 °C ∼ (decomp.) Anal Calcd. (%) for C₁₂H₂₂N₂O₃Pt: C, 32.95, H, 5.07; N, 6.40; Pt, 44.60 Found C, 32.89; H, 5.07; N, 6.49; Pt, 44.57 IR, ν (Nujol) : 3420 (w), 3210 (m), 3118 (m), 1637 (vs), 1343 (s), 1313 (m), 1305 (sh), 1211 (w), 1111 (w), 1097 (w), 1062 (m), 1032 (w), 1013 (w), 984 (w), 947 (w), 919 (w), 855 (w), 837 (w) cm⁻¹ ¹H-NMR (D₂O, external standard TMS δ): 1.33-3.73 (b, m cyclopentane+cyclohexane) Example 4 (1R,2R-Diaminocyclohexane)[2-hydroxy-2-methylbutyrato(2-)-O¹,O²-] platinum (II) (I-4) A solution of 4.59 mmol of the dinitrato (III) in water is treated in the same manner as Example 1. An aqueous solution of the resulting dihydroxy compound (II) is mixed with 544.5 mg (4.61 mmol) of 2-hydroxy-2-methylbutyric acid, and the solution is heated at 60 to 63°C for about 7 hours. The reaction mixture is concentrated under reduced pressure, and the residue is dissolved in methanol. The solution is subjected to silica gel column chromatography, and the eluate of Rf=0.57 (methanol) is collected. The solution is concentrated to about 2 ml and mixed with acetone to precipitate crystals, and the resulting crystals are collected. The crystals are washed twice with acetone and dried under reduced pressure to give 1.54 g (yield: 78.8%) of the objective compound (I-4) as white crystalline powder. mp. 240 °C ∼ (decomp.) Anal Calcd. (%) for C₁₁H₂₂N₂O₃Pt: C, 31.06; H, 5.21; N, 6.59; Pt, 45.86 Found (%) C, 31.18; H, 5.19; N, 6.28; Pt, 45.27 IR, ν (Nujol) : 3396 (b,m), 3204 (s), 3110 (s), 1639 (vs), 1341 (m), 1313 (w), 1261 (w), 1178 (m), 1131 (w), 1063 (w), 1032 (w), 926 (w), 829 (w), 664 (w) cm⁻¹ ¹H-NMR (D₂O, internal standard DSS δ): 1.024, 1.039* (t, 3H, -CH₂CH₃), 1.231, 1.230* (s, 3H, -CH₃), 1.1 - 1.7 (m, 8H, cyclohexane C₃, C₆-Hax, C₄, C₅-H₂, -CH₂CH₃), 2.04 (bm, 2H, cyclohexane, C₃, H₆-Heq), 2.30 (bm, 2H, cyclohexane, C₁, C₂-H) (*: symbol for geometrical isomer) Example 5 (1R,2R-Diaminocyclohexane)[2-hydroxy-2-ethylbutyrato(2-)-O¹,O²]-platinum (II) (I-5) A solution of 4.59 mmol of the dinitrato (III) in water is treated in the same manner as Example 1. An aqueous solution of the resulting dihydroxy compound (II) is mixed with 612.5mg (4.63 mmol) of 2-ethyl-2-hydroxybutyric acid, and the solution is treated in the same manner as in the Example 4 to collect the eluate of Rf=0.65 (methanol). The eluate is concentrated and the residue is cooled with ice. The precipitating pale yellow solid is collected by decantation, and dried at about 90 °C for 4 hours to give 1.158 g (yield: 57.4%) of the objective compound (I-5). mp. 220°C ∼ (decomp.) Anal Calcd. (%) for C₁₂H₂₄N₂O₃Pt: C, 32.80; H, 5.51; N, 6.37; Pt, 44.40 Found (%) C, 33.44; H, 5.71; N, 6.31; Pt, 44.03 IR ν (Nujol): 3196 (m), 3104 (m), 2424 (vw), 1602 (vs), 1319 (m), 1277 (m), 1210 (vw), 1177 (m), 1157 (m), 1128 (w), 1063 (m), 1034 (w), 974 (s), 920 (w), 861 (vw), 840 (m), 794 (w), 742 (w), 670 (m), 569 (w) cm⁻¹ ¹H-NMR (D₂O, internal standard DSS, δ) : 0.973, 0.99 (t, 6H, - CH₂CH₃x2), 1.05-1.63 (m, 10H, cyclohexane, C₅, C₄-H₂, C₃, C₆-Hax, -CH₂CH₃x2), 2.045 (bm, 2H, cyclohexane, C₃, C₆-Heq), 2.297 (bm, 2H, cyclohexane, C₁, C₂-H) Example 6 (1R,2R-Diaminocylohexane)[2-hydroxy-2-isobutyrato(2-)-O¹,O²]platinum (II) (I-6) To an aqueous solution of 2.72 mmol of the dihydroxy compound (II), 283.2 mg (2.72 mmol) of 2-hydroxyisobutyric acid are added, and the resulting solution is treated in the same manner as in Example 4 to give 661.8 mg (Yield : 59.0%) as pale yellow crystals. mp. 240°C ∼ (decomp.) Anal Calcd. (%) for C₁₀H₂₀N₂O₃Pt(H₂O) 0.5 ) C, 28.57; H, 5.04; N, 6.66; Pt, 46.41 Found (%) C, 28.79; H, 4.99; N, 6.80; Pt, 46.52 IR ν (Nujol) : 3410 (b,m), 3272 (m), 3132 (m), 1617 (s), 1544 (w), 1332 (m), 1262 (w), 1195 (m), 1170 (w), 1156 (w), 1130 (w), 1065 (w), 1035 (w), 968 (m), 920 (w), 894 (w), 860 (w), 832 (m), 772 (w), 677 (m) cm⁻¹ ¹H-NMR (D₂O, internal standard DSS δ): 1.297, 1.315 (sx2, 6H, -CH₃x2), 1.05-1.70 (m, 6H cyclohexane, C₃, C₆-Hax, C₄, C₅-H₂), 2.04 (bm, 2H, cyclohexane, C₃H₆-Heq), 2.30 (bm, 2H, cyclohexane, C₁, C₂-H) Example 7 (1R,2R-Diaminocyclohexane)[1-hydroxy-1-cyclohexanecarboxylato-(2-)-0¹,O²]platinum (II) (I-7) An aqueous solution of 8.33 mmol of dinitrato compound (III) is treated in the same manner as in Example 1 to give about 100 ml of aqueous solution of the dihydroxy compound (II). The solution is mixed with 1.2 g (8.34 mmol) of 1-hydroxy-1-cyclohexanecarboxylic acid, and the mixture is reacted at 60-65 °C for 6 hours. The reaction mixture is concentrated to dryness under reduced pressure, and the resulting residue is dissolved in ethanol. It is subjected to silica gel column chromatography, and eluate of Rf=0.59-0.60 (methanol) is collected. The eluate is recrystallized from ethanol to give 2.1 g (Yield : 50.6 %) of the objective compound (I-7). mp. 240°C ∼ (decomp.) Anal Calcd. (%) for C₁₃H₂₄N₂O₃Pt·C₂H₅OH: C, 36.21; H, 6.08; N, 5.63; Pt, 39.21 Found C, 34.70; H, 5.99; N, 5.86; Pt, 39.13 IR ν (Nujol) : 3658 (w), 3356 (m) 3232 (s), 3200 (sh), 3124 (s), 1624 (vs), 1602 (sh), 1345 (m), 1305 (s), 1290 (s), 1269 (m), 1260 (m), 1222 (m), 1192 (w), 1165 (m), 1152 (m), 1126 (w), 1090 (w), 1066 (m), 1046 (m), 1031 (m), 980 (m), 932 (vw), 912 (vw), 882 (vw), 839 (w), 819 (w), 740 (m), 716 (w) ¹HNMR (D₂O, DSS, δ ): 1.02-1.64 (m, cyclohexanecarboxylato (OH)); 1.02-2.40 (m, 1R, 2R-cyclohexane, 10H) Experiment 1 Antitumor activity against murine leukemia cells (L1210) and cisplatin-resistant murine leukemia cells (L1210/CDDP): (Test method) Murine leukemia L1210 (or L1210/CDDP) ascitic cells (1x10⁵ cells) (5x10⁵ cells for L1210/CDDP) were intraperitoneally inoculated to BDF₁ mice (each group consisting of 6-10 mice), and on the next day a predetermined amount of the test compound was intraperitoneally administered. 0.9 % physiological saline was used as a solvent for injection. (Test compounds) A: (1R,2R-Diaminocyclohexane)[1-hydroxy-1-cyclopentanecarboxylato(2-)-O¹,O²]platinum (II) B: (1R,2R-Diaminocyclohexane)[1-hydroxy-1-cyclopropanecarboxylato(2-)-O¹,O²]platinum (II) C: (1R,2R-Diaminocyclohexane)[2-hydroxy-2-methylbutyrato(2-)-O¹, O²]platinum(II) D: Cisplatin (control) E: Carboplatin (control) (Judging method) From the average survival days (a) in each test group and those (b) of non-treated control group, the increase in lifespan (ILS) was calculated according to the following formula. As compared to the non-treated control group, the dose achieving a 30% ILS (ILS₃₀) and the dose achieving the maximum ILS (ILS max ) were obtained, from which the chemotherapy index (CI) was calculated. The greater the CI value, the more effective the drug. (Results) The results are shown in Tables 1 to 4. Antitumor effect on L1210/CDDP Test compound Dose (mg/kg) Number of mice ILS (%) Number of mice surviving 30 days or more A 0 10 ― ― 5 6 1 ― 10 6 5 ― 20 6 > 50 2 40 6 > 56 2 80 6 > 110 4 160 7 1 ― B 0 9 ― ― 5 7 6 ― 10 7 14 ― 20 7 4 ― 40 7 > 93 3 80 7 > 179 6 160 7 - 16 ― Antitumor effect on L1210/CDDP and solubility in water Test compound ILS₃₀ (mg/kg) ILS max (mg/kg) CI Solubility (mg/ml) A 14.5 80 5.5 > 500 B 24 80 3.3 30 D ineffective 1.4 E ineffective 16 Antitumor effect on L1210 Test compound Dose (mg/kg) Number of mice ILS (%) Number of mice survived 30 days or more A 0 10 ― ― 5 7 10 ― 10 7 16 ― 20 7 19 ― 40 7 37 1 80 7 > 81 3 160 7 > 168 1 320 7 14 ― B 0 10 ― ― 10 7 10 ― 20 7 21 ― 40 7 22 ― 80 7 66 ― 160 7 > 83 2 Antitumor effect on L1210 Test compound ILS₃₀ (mg/kg) ILS max (mg/kg) CI A 31 160 5.2 B 45 160 3.6 D 2.7 10 3.7 Experiment 2 Antitumor activity against Colon tumor 38 : (Test method) Tumor segments of Colon tumor 38 were transplanted beneath the dorsal skin of BDF₁ mice (6 to 10 mice in each group), and the test compounds were intravenously administered the next day and on the 8th day after the next day, respectively. 0.9% physiological saline was used as injection solvent. (Test compounds) Test Compounds A, C, D and E were same as those used in Experiment 1. (Evaluation of the Effect) The chemotherapy index (CI) was determined from the dose resulting in 50% growth inhibition in the mean tumor size in each test group, as compared to that of non-treated control group (ED₅₀), and the acute toxicity level (LD₅₀) according to the following formula: The greater the CI value, the more effective the drug. (Results) Antitumor activity against Colon tumor 38 Test compound ED₅₀ (mg/kg) LD₅₀ (mg/kg) CI A 164.9 452.5 2.7 C 106.2 452.5 4.3 D 18.3 31.1 1.7 E Ineffective Experiment 3 Influence on murine nucleated bone marrow cell count, megakaryocyte count and platelet count in peripheral blood: (Test method) After a single intravenous administration of the test compounds to male CDF₁ mice (7 weeks old), hemotoxicity was investigated by counting the nucleated bone marrow cells in femora (NBMC), megakaryocytes (MEG) and platelets (PLT) in peripheral blood. Measuring timing was taken when the three indices got to the minimal value, namely 4 days after administration for NBMC, and 7 days after for MEG and PLT. (Test compounds) Test Compounds A, D and E were the same as those used in Experiment 1. (Results) The results are shown in Table 6. Hemotoxicity was shown as changes in each count of nucleated bone marrow cells (NBMC), megakaryocytes (MEG) and platelets (PLT) in peripheral blood induced by administration of test compounds. Hemotoxicity was expressed as the ratio of the value of each index in the test group, to that of the non-treated conrol group in percentage. The smaller the value, the greater the hemotoxicity. Experiment 4 Evaluation of nephrotoxicity in mice: (Test method) After a single intravenous administration of Test Compound A to male CDF₁ mice (6 weeks old) at a dose of 160 or 320 mg/kg*, levels of creatinine and urea nitrogen in plasma were measured. The mice were presented for pathological examination of their kidneys four days after administration. (*: 320 mg/kg would be a lethal dose if the observation period was further extended.) (Results) The results are shown in the Table 7.

Claims: Claims for the following Contracting States : AT, BE, CH, DE, DK, FR, GB, IT, LI, LU, NL, SE A compound of the formula: wherein R¹ and R² are identical or different lower alkyl groups, or R¹ and R² taken together form a -(CH₂)m- bridge, and m is an integer from 2 to 5. The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[1-hydroxy-1-cyclopropanecarboxylato(2-)-O¹,O²] platinum (II). The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[1-hydroxy-1-cyclopentanecarboxylato(2-)-O¹,O²] platinum (II). The compound claimed in Claim 1, namely (1,2-diaminocyclohexane)[1-hydroxy-1-cyclopentanecarboxylato(2-)-O¹,O²] platinum (II). The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[2-hydroxy-2-methylbutyrato(2-)-O¹,O²]platinum (II). The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[2-hydroxy-2-ethylbutyrato(2-)-O¹,O²]platinum (II). The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[2-hydroxy-2-isobutyrato(2-)-O¹,O²]platinum (II). The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[1-hydroxy-1-cyclohexanecarboxylato(2-)-O¹,O²] platinum (II). An antitumor agent comprising the compound claimed in Claim 1 as an active ingredient. A process for preparing the compounds claimed in any of Claims 1 to 8, which comprises reacting a compound (III) of the formula: with an anion exchange resin to give a compound (II) of the formula: and reacting the compound (II) with a compound (IV) of the formula: HOCR¹R²COOH (IV) wherein R¹ and R² have the meaning defined above. Use of the compounds of any of Claims 1 to 8 for preparing a pharmaceutical composition with antitumor activity. Claims for the following Contracting State : ES A process for preparing a compound of the formula: wherein R¹ and R² are identical or different lower alkyl groups, or R¹ and R² taken together form a -(CH₂)m- bridge, and m is an integer from 2 to 5, which comprises reacting a compound (III) of the formula: with an anion exchange resin to give a compound (II) of the formula: and reacting the compound (II) with a compound (IV) of the formula: HOCR¹R²COOH (IV) wherein R¹ and R² have the meaning defined above. The process according to Claim 1 for preparing (1R,2R-diaminocyclohexane)[1-hydroxy-1-cyclopropanecarboxylato(2-) -O¹,O²]platinum (II). The process according to Claim 1 for preparing (1R,2R-diaminocyclohexane)[1-hydroxy-1-cyclopentanecarboxylato(2-) -O¹,O²]platinum (II). The process according to Claim 1 for preparing (1,2-diaminocyclohexane)[1-hydroxy-1-cyclopentanecarboxylato(2-) -O¹,O²]platinum (II). The process according to Claim 1 for preparing (1R,2R-diaminocyclohexane)[2-hydroxy-2-methylbutyrato(2-)-O¹,O²] platinum (II). The process according to Claim 1 for preparing (1R,2R-diaminocyclohexane)[2-hydroxy-2-ethylbutyrato(2-)-O¹,O²] platinum (II). The process according to Claim 1 for preparing (1R,2R-diaminocyclohexane)[2-hydroxy-2-isobutyrato(2-)-O¹,O²]platinum (II). The process according to Claim 1 for preparing (1R,2R-diaminocyclohexane)[1-hydroxy-1-cyclohexanecarboxylato(2-)-O¹,O²]platinum (II). Claims for the following Contracting State : GR A compound of the formula: wherein R¹ and R² are identical or different lower alkyl groups, or R¹ and R² taken together form a -(CH₂)m- bridge, and m is an integer from 2 to 5. The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[1-hydroxy-1-cyclopropanecarboxylato(2-)-O¹,O²] platinum (II). The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[1-hydroxy-1-cyclopentanecarboxylato(2-)-O¹,O²] platinum (II). The compound claimed in Claim 1, namely (1,2-diaminocyclohexane)[1-hydroxy-1-cyclopentanecarboxylato(2-)-O¹,O²] platinum (II). The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[2-hydroxy-2-methylbutyrato(2-)-O¹,O²]platinum (II). The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[2-hydroxy-2-ethylbutyrato(2-)-O¹,O²]platinum (II). The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[2-hydroxy-2-isobutyrato(2-)-O¹,O²]platinum (II). The compound claimed in Claim 1, namely (1R,2R-diaminocyclohexane)[1-hydroxy-1-cyclohexanecarboxylato(2-)-O¹,O²] platinum (II). A process for preparing the compounds claimed in any of Claims 1 to 8, which comprises reacting a compound (III) of the formula: with an anion exchange resin to give a compound (II) of the formula: and reacting the compound (II) with a compound (IV) of the formula: HOCR¹R²COOH (IV) wherein R¹ and R² have the meaning defined above. Use of the compounds of any of Claims 1 to 8 for preparing a pharmaceutical composition with antitumor activity.

Inventors: MURAOKA YOSHIHIRO, SHIRATORI OSAMU, TOTANI TETSUSHI, MURAOKA, YOSHIHIRO, SHIRATORI, OSAMU, TOTANI, TETSUSHI
Applicants: SHIONOGI & CO, SHIONOGI SEIYAKU KABUSHIKI KAISHA TRADING UNDER THE NAME OF  SHIONOGI & CO. LTD.
Application year: 1990
Main classification: C07C59
IPC codes: A61P35, A61K31, C07C62, C07C211, A61K33, C07F15, C07C59