NOVEL PLATINUM COMPLEXES

Abstract: A diamine platinum (II) complex represented by the general formula [wherein R₁, R₂, R₃ and R₄ are each a hydrogen atom or a lower alkyl group; and two X's are each a halogen atom or jointly form a group represented by (wherein R₅ and R₆ are each a hydrogen atom or a lower alkyl group) or a group represented by (wherein m is l or 2)] is useful as an anti-tumour agent.

Description: BACKGROUND OF THE INVENTION l. FIELD OF THE INVENTION This invention relates to novel platinum complexes having an antitumor effect. 2. DESCRIPTION OF THE PRIOR ART With respect to platinum complexes having an antitumor effect, cis-Platin (cis-dichlorodiammineplatinum) is already available commercially and is being applied to many cases because of its striking effect. Other platinum complexes having an antitumor effect as well are reported in several papers. Of these, platinum complexes having a straight alkyl diamine as a ligand are limited to those having a ligand represented by the general formula H₂N-C n R 2n -NH₂ (I) (wherein R is a hydrogen atom or a substituent such as an alkyl group, a hydroxyl group or the like and n is an integer of l to 3). [e.g. Japanese Patent Application Kokai (Laid-Open) No. l564l6/l982 or l03l92/l98l]. As mentioned above, cis-Platin is commercially available as a platinum complex carcinostatic agent. However, cis-Platin has high renal toxicity, which possess a dose limiting factor. Therefore, in administering cis-­ Platin, it is requisite that a large amount of water be administered before and during the administration of cis-Platin and that cis-Platin be administered together with a diuretics and over a long period of time. Further, cis-Platin, having low solubility in water and dissolving in water slowly, is supplied at a very low concentration. Furthermore, cis-Platin has very high vomitting toxicity, posing a problem in cure. Because of these drawbacks of cis-Platin, many researches have been conducted in order to find a platinum complex having an antitumor activity which has high solubility in water, low renal toxicity and low vomitting toxicity. However, no platinum complex has been applied practically till now. SUMMARY OF THE INVENTION When a l,4-butanediamine or its derivative reacts with a platinum atom to form a coordination compound through the two nitrogen atoms of the diamine, there is formed a ring structure by 7 atoms including the platinum atom, namely, a 7-membered ring structure as shown in the formula (II) which appears later. In general, complexes having such a 7-membered ring structure are very difficult to synthesize in the usual way. As a result of an extensive research, the present inventors succeeded in the synthesis of various platinum (II) complexes having a l,4-­ butanediamine or its derivative as a ligand and found that these complexes have an antitumor effect and that their renal toxicity and vomitting toxicity are remarkably lower than those of cis-Platin. The present invention has been completed based on the above finding. The present invention relates to diamine platinum (II) complexes represented by the general formula (II) [wherein R₁, R₂, R₃ and R₄ are each a hydrogen atom or a lower alkyl group; and two X's are each a halogen atom or jointly form a group represented by (wherein R₅ and R₆ are each a hydrogen atom or a lower alkyl group) or a group represented by (wherein m is l or 2)]. DETAILED DESCRIPTION OF THE INVENTION In the above general formula (II), the lower alkyls represented by R₁, R₂, R₃, R₄, R₅ and R₆ include, for example, alkyl groups of l to 4 carbon atoms. Specifically, there are mentioned a methyl group, an ethyl group, an n-propyl group, an isopropyl group, etc. In the general formula (II), the halogen atom represented by X includes Cl, Br, etc. Of the compounds of the present invention represented by the general formula (II), preferable are those where two X's jointly form a group represented by Also preferable are those where R₁ and R₂ represent each a hydrogen atom. Typical examples of the compounds represented by the general formula (II) are shown below. However, the present invention is not restricted to these Examples. 1. cis-Dichloro-l,4-butanediamine platinum. 2. cis-Cyclobutane-l,l-dicarboxylato-l,4-­ butanediamine platinum. 3. cis-4-Oxacyclohexane-l,l-dicarboxylato-l,4-­ butanediamine platinum. 4. cis-Dichloro-l-methyl-l,4-butanediamine platinum. 5. cis-Oxalato-l-methyl-l,4-butanediamine platinum. 6. cis-Malonato-l-methyl-l,4-butanediamine platinum. 7. cis-Cyclobutane-l,l-dicarboxylato-l-methyl-l,4-­ butanediamine platinum. 8. cis-Dimethylmalonato-l-methyl-l,4-butanediamine platinum. 9. cis-Ethylmalonato-l-methyl-l,4-butanediamine platinum. l0. cis-Dichloro-l-ethyl-l,4-butanediamine platinum. 11. cis-Cyclobutane-l,l-dicarboxylato-l-ethyl-l,4-­ butanediamine platinum. 12. cis-4-Oxacyclohexane-l,l-dicarboxylato-l-ethyl-­ l,4-butanediamine platinum. 13. cis-Dichloro-2-methyl-l,4-butanediamine platinum. 14. cis-Malonato-2-methyl-l,4-butanediamine platinum. 15. cis-Cyclobutane-l,l-dicarboxylato-2-methyl-l,4-­ butanediamine platinum. 16. cis-4-Oxacyclohexane-l,l-dicarboxylato-2-methyl-­ l,4-butanediamine platinum. 17. cis-Dimethylmalonato-2-methyl-l,4-butanediamine platinum. 18. cis-Ethylmalonato-2-methyl-l,4-butanediamine platinum. 19. cis-Dichloro-2,2-dimethyl-l,4-butanediamine platinum. 20. cis-Oxalato-2,2-dimethyl-l,4-butanediamine platinum. 2l. cis-Malonato-2,2-dimethyl-l,4-butanediamine platinum. 22. cis-Cyclobutane-l,l-dicarboxylato-2,2-dimethyl-­ l,4-butanediamine platinum. 23. cis-4-Oxacyclohexane-l,l-dicarboxylato-2,2-­ dimethyl-l,4-butanediamine platinum. 24. cis-Dimethylmalonato-2,2-dimethyl-l,4-butane­ diamine platinum. 25. cis-Dichloro-l,l-dimethyl-l,4-butanediamine platinum. 26. cis-Oxalato-l,l-dimethyl-l,4-butanediamine platinum. 27. cis-Cyclobutane-l,l-dicarboxylato-l,l-dimethyl-­ l,4-butanediamine platinum. 28. cis-Dimethylmalonato-l,l-dimethyl-l,4-butane­ diamine platinum. 29. cis-Dichloro-2-ethyl-l,4-butanediamine platinum. 30. cis-Oxalato-2-ethyl-l,4-butanediamine platinum. 3l. cis-Malonato-2-ethyl-l,4-butanediamine platinum. 32. cis-Cyclobutane-l,l-dicarboxylato-2-ethyl-l,4-­ butanediamine platinum. 33. cis-Dimethylmalonato-2-ethyl-l,4-butanediamine platinum. 34. cis-Oxalato-2-isopropyl-l,4-butanediamine platinum. 35. cis-Dichloro-l,2-dimethyl-l,4-butanediamine platinum. The compounds of the present invention can be produced by utilizing a known process, for example, a process described in Indian J. Chem., 8 , l93 (l970) but it is necessary to modify the reaction method. The compounds of the present invention can be produced by reacting a diamine represented by the general formula (wherein R₁, R₂, R₃ and R₄ have the same definitions as given previously, respectively) with M₂Pt(Hal)₄ (wherein M is an atom capable of becoming a monovalent cation and Hal is a halogn atom) to obtain a dihalogeno­ diamine platinum complex represented by the general formula (wherein R₁, R₂, R₃ and R₄ and Hal have the same defini­ tions as given previously, respectively) and, as necessary, reacting the dihalogenodiamine platinum complex with silver ions in the presence of water to convert to a diaquacomplex and reacting the diaquacomplex with a dicarboxylic acid or a salt thereof. The production process of the compounds of the present invention will be described in more detail. (In the above, M is an atom capable of becoming a monovalent cation, such as Na, K, Cs or the like; Hal is a halogen atom such as Cl, Br, I or the like; R₁, R₂, R₃ and R₄ have the same definitions as given previously, respectively.) As shown in the above reaction scheme, a tetra­ halogenoplatinate and a diamine are reacted in an aqueous medium, preferably water to obtain a dihalogenodiamine platinum. Water is used in an amount of preferably 5 to 500 liters, more preferably 5 to l60 liters, particularly preferably 20 to 80 liters per l mole of the tetrahalogeno­ platinate. The diamine is used in an amount of preferably 0.5 to 4 moles, particularly preferably 0.9 to l.2 moles per l mole of the tetrahalogenoplatinate. This reaction is conducted at 0° to l00°C, preferably 50° to 70°C with stirring. In conducting the reaction, it is preferable that an aqueous tetrahalogenoplatinate solution and an aqueous diamine solution are gradually added to distilled water separately at the same time. The addition is conducted preferably slowly and usually takes l to 6 hours. The reaction can be conducted in an atmosphere of air but preferably under a stream of an inert gas such as nitrogen or the like. Next, as shown in the following reaction scheme, the dihalogenodiamine platinum (IIa) is suspended in water and reacted with silver ions and the resulting silver halide precipitate is removed by filtration to obtain an aqueous solution of a diaquacomplex (III). The water for suspending the dihalogenodiamine complex (IIa) can be used in an appropriate amount but the amount preferably is 5 to l50 ℓ per l mole of the complex (IIa). The amount of silver ion has no particular restric­ tion but, from an economical standpoint, is preferred to be 0.5 to 6 equivalents per l equivalent of the dihalogeno­ diamine complex (IIa). In order to avoid an excessive addition, the amount particularly preferably is l.9 to 2 equivalents per l equivalent of the dihalogenodiamine complex (IIa). The reaction is conducted at 0° to l00°C, preferably 60° to 80°C with stirring. As the compound generating silver ion, there can be used, for example, silver nitrate, silver sulfate, silver perchlorate and silver acetate. Finally, the diaquacomplex (III) is reacted with a dicarboxylic acid salt, a dicarboxylic acid monohydrogen salt or a dicarboxylic acid. For example, the reaction is carried out by adding an aqueous solution containing an appropriate amount of a dicarboxylic acid salt, a dicarboxylic acid monohydrogen salt or a dicarboxylic acid to the aqueous solution of the diaquacomplex (III). Said salt or acid is used in an amount of preferably 0.5 to l0 moles, particularly preferably 0.9 to 6 moles per l mole of the diaquacomplex (III). The reaction can be conducted at 0° to l00°C but preferably is conducted at 40° to 90°C to obtain a compound (IIb). (III) + Dicarboxylic acid salt or dicarboxylic acid monohydrogen salt or dicarboxylic acid (In the above, X' is same as X other than halogen atoms.) The structure of the compounds (II) of the present invention was confirmed by various analysis methods such as elemental analysis, infrared absorption spectrometry, fast atom bombardment mass spectrometry (FAB-MS Pt¹⁹⁴) and the like. The compounds of the present invention have very low renal toxicity and very low vomitting toxicity, have high solubility in water, are dissolved in water rapidly, have an excellent antitumor effect, and accordingly are useful as an antitumor agent. When they are used as an antitumor agent, they can be administered as an injection, an oral drug and the like. Moreover, the compounds of the present invention are stable in air at room temper­ ature, thus requiring no low temperature storage. The embodiments of the present invention will be described below by way of Examples. However, the present invention is in no way restricted to these Example. Example l cis-Dichloro-l,4-butanediamine platinum (Compound No. l) l0g of potassium tetrachloroplatinate (II) was dissolved in 350 ml of water. Thereto was added a solu­ tion of l6 g of potassium iodide dissolved in 50 ml of water, with stirring. Stirring was continued for 5 minutes at 35°C to obtain a black aqueous solution of potassium tetraiodoplatinate (II). Separately, 2.l2 g of l,4-butanediamine was dissolved in 400 ml of water to obtain an aqueous l,4-butanediamine solution. 250 ml of water was placed in a flask. Into this water, were dropwise added the aqueous potassium tetraiodoplatinate (II) solution and the aqueous l,4-butanediamine solution both prepared above, simultaneously for 2 hours at the constant rates, respectively while stirring at 60°C. The resulting reddish brown crystals were collected by filtra­ tion and washed with water, ethanol and ether in this order. The crystals were then dried under vacuum to obtain 9.74 g (yield: 75.3%) of crystals of cis-diiodo-­ l,4-butanediamine platinum. l g of this product was suspended in 20 ml of water. Thereto was added a solution of 620 mg of silver nitrate dissolved in l0 ml of water. They were stirred for 20 minutes at 60°C for reaction. The reaction mixture was cooled to room temperature and filtered to remove silver iodide. The silver iodide removed was washed with water. The filtrate and the washings were mixed together, and thereto was added a solution of 653 mg of sodium chloride dissolved in 5 ml of water. The mixture was stirred for l0 minutes at room temperature. The resulting yellow crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. l. Yield: 538 mg Elementary analysis Calculated (%): C l3.57, H 3.42, N 7.9l Pt 55.09 Found (%): C l3.44, H 3.56, N 8.04, Pt 54.8 FAB-MS: (M + H)⁺ = 353 Example 2 cis-Cyclobutane-l,l-dicarboxylato-l,4-­ butanediamine Platinum (Compound No. 2) In Example l, the solution of 653 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 537 mg of l,l-cyclobutane-­ dicarboxylic acid in 7.26 ml of l N aqueous sodium hydroxide solution. The mixture resulting from addition of this solution was stirred for 2 hours at 60°C for reaction. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. 2. Yield: 457 mg Elementary analysis Calculated (%): C 28.24, H 4.27, N 6.59, Pt 45.86 Found (%): C 28.56, H 4.4l, N 6.48, Pt 45.2 FAB-MS: (M + H)⁺ = 425 Example 3 cis-4-Oxacyclohexane-l,l-dicarboxylato-l,4-­ butanediamine platinum (Compound No. 3) In Example l, the solution of 653 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 324 mg of 4-oxacyclohexane-­ l,l-dicarboxylic acid in 7.26 ml of l N aqueous sodium hydroxide solution. The mixture resulting from addition of this solution was stirred for 2 hours at 60°C for reaction. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. 3. Yield: 493 mg Elementary analysis Calculated (%): C 29.0l, H 4.43, N 6.l5, Pt 42.84 Found (%): C 28.76, H 4.62, N 6.04, Pt 42.4 FAB-MS: (M + H)⁺ = 455 Example 4 cis-Dichloro-l-methyl-l,4-butanediamine platinum (Compound No. 4) In Example l, 2.46 g of l-methyl-l,4-butane­ diamine was used in place of 2.l2 g of l,4-butanediamine and there were obtained 9.64 g (yield: 72.6%) of reddish brown crystals of cis-diiodo-l-methyl-l,4-butanediamine platinum. In the same manner as in Example l except that there were used l g of this product, 604 mg of silver nitrate and 636 mg of sodium chloride, a compound No. 4 was obtained as yellow crystals. Yield: 400 mg Elementary analysis Calculated (%): C l6.3l, H 3.83, N 7.6l, Pt 52.99 Found (%): C l6.57, H 3.98, N 7.8l, Pt 53.0 FAB-MS:(M + H)⁺ = 367 Example 5 cis-Oxalato-l-methyl-l,4-butanediamine platinum (Compound No. 5) In Example 4, 636 mg of sodium chloride was replaced by 669 mg of potasium oxalate monohydrate. After addition of a solution of 669 mg of this potassium oxalate monohydrate dissolved in 5 ml of water, the resulting mixture was stirred for 2 hours at 60°C. The resulting mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. 5. Yield: 426 mg Elementary analysis Calculated (%): C 2l.82, H 3.66, N 7.27, Pt 50.63 Found (%): C 22.0l, H 3.7l, N 6.98, Pt 52.0 FAB-MS: (M + H)⁺ = 385 Example 6 cis-Malonato-l-methyl-l,4-butanediamine platinum (Compound No. 6) In Example 4, the solution of 636 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 378 mg of malonic acid in 6.90 ml of l N aqueous sodium hydroxide solution. The mixture resulting from addition of this solution was stirred for 8 hours at 50°C. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The result­ ing white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. 6. Yield: 305 mg Elementary analysis Calculated (%): C 24.06, H 4.04, N 7.02, Pt 48.85 Found (%): C 24.38, H 4.27, N 6.80, Pt 48.4 FAB-MS: (M + H)⁺ = 399 Example 7 cis-Cyclobutane-l,l-dicarboxylato-l-methyl-­ l,4-butanediamine platinum (Compound No. 7) In Example 4, the solution of 636 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 523 mg of cyclobutane-l,l-­ dicarboxylic acid in 7.08 ml of l N aqueous sodium hydroxide solution. The mixture resulting from addition of this solution was stirred for 2 hours at 60°C. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. 7. Yield: 608 mg Elementary analysis Calculated (%): C 30.07, H 4.59, N 6.38, Pt 44.40 Found (%): C 29.88, H 4.44, N 6.53, Pt 44.l FAB-MS: (M + H)⁺ = 439 Example 8 cis-Dimethylmalonato-l-methyl-l,4-butanediamine platinum (Compound No. 8) In Example 4, the solution of 636 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 480 mg of dimethylmalonic acid in 7.08 ml of l N aqueous sodium hydroxide solution. The mixture resulting from addition of this solution was stirred for 6 hours at 50°C. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. 8. Yield: 532 mg Elementary analysis Calculated (%): C 28.ll, H 4.72, N 6.55, Pt 45.65 Found (%): C 28.40, H 4.9l, N 6.30, Pt 46.4 FAB-MS: (M + H)⁺ = 427 Example 9 cis-Ethylmalonato-l-methyl-l,4-butanediamine platinum (Compound No. 9) In Example 4, the solution of 636 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 480 mg of ethylmalonic acid in 7.08 ml of l N aqueous sodium hydroxide solution. The mixture resulting from addition of this solution was stirred for 2 hours at 60°C. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. 9. Yield: 575 mg Elementary analysis Calculated (%): C 28.ll, H 4.72, N 6.55, Pt 45.65 Found (%): C 27.88, H 4.65, N 6.48, Pt 46.l FAB-MS: (M + H)⁺ = 427 Example l0 cis-Dichloro-l-ethyl-l,4-butanediamine platinum (Compound No. l0) In Example l, 2.l2 g of l,4-butanediamine was replaced by 2.80 g of l-ehtyl-l,4-butanediamine and there were obtained l0.90 g (yield: 80.l%) of reddish brown crystals of cis-diiodo-l-ethyl-l,4-butanediamine platinum. In the same manner as in Example l except that l g of this product, 589 mg of silver nitrate and 620 mg of sodium chloride were used, a compound No. l0 was obtained as yellow crystals. Yield: 394 mg Elementary analysis Calculated (%): C l8.86, H 4.22, N 7.33, Pt 5l.04 Found (%): C l8.99, H 4.50, N 7.55, Pt 50.l FAB-MS: (M + H)⁺ = 38l Example ll cis-Cyclobutane-l,l-dicarboxylato-l-ethyl-l,4-­ butanediamine platinum (Compound No. ll) In Example l0, the solution of 620 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 5l0 mg of cyclobutane-­ dicarboxylic acid in 6.90 ml of l N aqueous sodium hydroxide solution. The mixture resulting from addition of this solution was stirred for 2 hours at 60°C. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. ll. Yield: 342 mg Elementary analysis Calculated (%): C 3l.79, H 4.89, N 6.l8, Pt 43.03 Found (%): C 3l,53, H 4.7l, N 6.36, Pt 42.6 FAB-MS: (M + H)⁺ = 453 Example l2 cis-4-Oxacyclohexane-l,l-dicarboxylato-l-ethyl-­ l,4-butanediamine platinum (Compound No. l2) In Example l0, the solution of 620 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 6l6 mg of 4-oxacyclohexane-­ l,l-dicarboxylic acid in 7.08 ml of l N aqueous sodium hydroxide solution. The mixture resulting from addition of this solution was stirred for 2 hours at 60°C. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. l2. Yield: 32l mg Elementary analysis Calculated (%): C 32.30, H 5.00, N 5.79, Pt 40.35 Found (%): C 32.5l, H 5.l2, N 6.0l, Pt 39.2 FAB-MS: (M + H)⁺ = 483 Example l3 cis-Dichloro-2-methyl-l,4-butanediamine platinum (Compound No. l3) In Example l, 2.l2 g of l,4-butanediamine was replaced by 2.46 g of 2-methyl-l,4-butanediamine and there were obtained 9.94 g (yield: 74.9%) of reddish brown crystals of cis-diiodo-2-methyl-l,4-butanediamine platinum. In the same manner as in Example l except that l g of this product, 604 mg of silver nitrate and 636 mg of sodium chloride were used, a compound No. l3 was obtained as yellow crystals. Yield: 238 mg Elementary analysis Calculated (%): C l6.3l, H 3.83, N 7.6l, Pt 52.99 Found (%): C l6.l5, H 3.70, N 7.44, Pt 53.l FAB-MS: (M + H)⁺ = 367 Example l4 cis-Malonato-2-methyl-l,4-butanediamine platinum (Compound No. l4) In Example l3, the solution of 636 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 227 mg of malonic acid in 4.36 ml of l N aqueous sodium hydroxide solution. The mixture resulting from addition of this solution was stirred for 2 hours at 60°C. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. l4. Yield: l25 mg Elementary analysis Calculated (%): C 24.06, H 4.04, N 7.02, Pt 48.85 Found (%): C 24.22, H 3.99, N 7.4l, Pt 49.4 FAB-MS: (M + H)⁺ = 399 Example l5 cis-Cyclobutane-l,l-dicarboxylato-2-methyl-l,4-­ butanediamine platinum (Compound No. l5) A compound No. l5 was obtained as white crystals in the same manner as in Example l4 except that the solu­ tion obtained by dissolving 227 mg of malonic acid in 4.36 ml of l N aqueous sodium hydroxide solution was replaced by a solution obtained by dissolving 523 mg of cyclobutane-l,l-dicarboxylic acid in 7.29 ml of l N aqueous sodium hydroxide solution. Yield: l3l mg Elementary analysis Calculated (%): C 30.07, H 4.59, N 6.38, Pt 44.40 Found (%): C 30.20, H 4.3l, N 6.l5, Pt 44.5 FAB-MS: (M + H)⁺ = 439 Example l6 cis-4-Oxacyclohexane-l,l-dicarboxylato-2-methyl-­ l,4-butanediamine platinum (Compound No. l6) A compound No. l6 was obtained in the same manner as in Example l5 except that 523 mg of cyclobutane-­ l,l-dicarboxylic acid was replaced by 632 mg of 4-­ oxacyclohexane-l,l-dicarboxylic acid. Yield: l7l mg Elementary analysis Calculated (%): C 30.7l, H 4.72, N 5.97, Pt 4l.56 Found (%): C 30.28, H 4.88, N 6.l0, Pt 42.0 FAB-MS: (M + H)⁺ = 469 Example l7 cis-Dimethylmalonato-2-methyl-l,4-butanediamine platinum (Compound No. l7) A compound No. l7 was obtained in the same manner as in Example l5 except that 523 mg of cyclobutane-­ l,l-dicarboxylic acid was replaced by 480 mg of dimethylmalonic acid. Yield: l4l mg Elementary analysis Calculated (%): C 28.ll, H 4.72, N 6.56, Pt 45.65 Found (%): C 27.80, H 4.52, N 6.26, Pt 45.4 FAB-MS: (M + H)⁺ = 427 Example l8 cis-Ethylmalonato-2-methyl-l,4-butanediamine platinum (Compound No. l8) A compound No. l8 was obtained in the same manner as in Example l5 except that 523 mg of cyclobutane-­ l,l-dicarboxylic acid was replaced by 480 mg of ethyl­ malonic acid. Yield: l24 mg Elementary analysis Calculated (%): C 28.ll, H 4.72, N 6.56, Pt 45.65 Found (%): C 27.60, H 4.9l, N 6.l0, Pt 45.2 FAB-MS: (M + H)⁺ = 427 Example l9 cis-Dichloro-2,2-dimethyl-l,4-butanediamine platinum (Compound No. l9) In Example l, 2.l2 g of l,4-butanediamine was replaced by 2.80 g of 2,2-dimethyl-l,4-butanediamine and there were obtained ll.20 g (yield: 82.3%) of yellowish brown crystals of cis-diiodo-2,2-dimethyl-l,4-butane­ diamine platinum. In the same manner as in Example l except that l g of this product, 589 mg of silver nitrate and 620 mg of sodium chloride were used, a compound No. l9 was obtained as yellow crystals. Yield: 283 mg Elementary analysis Calculated (%): C l8.86, H 4.22, N 7.33, Pt 5l.04 Found (%): C l9.l2, H 4.03, N 7.0l, Pt 50.8 FAB-MS: (M + H)⁺ = 38l Example 20 cis-Oxalato-2,2-dimethyl-l,4-butanediamine platinum (Compound No. 20) In Example l9, the solution of 620 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water. The mixture resulting from addition of this solution was stirred for 2 hours at 60°C. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. 20. Yield: 448 mg Elementary analysis Calculated (%): C 24.06, H 4.04, N 7.02, Pt 48.85 Found (%): C 23.99, H 4.ll, N 6.86, Pt 49.3 FAB-MS: (M + H)⁺ = 399 Example 2l cis-Malonato-2,2-dimethyl-l,4-butanediamine platinum (Compound No. 2l) A compound No. 2l was obtained as white crystals in the same manner as in Example 20 except that the solution of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water was replaced by a solution obtained by dissolving 368 mg of malonic acid in 6.90 ml of l N aqueous sodium hydroxide solution. Yield: 33l mg Elementary analysis Calculated (%): C 26.l5, H 4.39, N 6.78, Pt 47.20 Found (%): C 26.5l, H 4.55, N 6.4l, Pt 46.l FAB-MS: (M + H)⁺ = 4l3 Example 22 cis-Cyclobutane-l,l-dicarboxylato-2,2-dimethyl-­ l,4-butanediamine platinum (Compound No. 22) A compound No. 22 was obtained as white crystals in the same manner as in Example 20 except that the solu­ tion of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water was replaced by a solution obtained by dissolving 5l0 mg of cyclobutane-l,l-dicarboxylic acid in 6.90 ml of l N aqueous sodium hydroxide solution. Yield: 375 mg Elementary analysis Calculated (%): C 3l.79, H 4.89, N 6.l8, Pt 43.03 Found (%): C 3l.8l, H 5.0l, N 6.36, Pt 43.2 FAB-MS: (M + H)⁺ = 453 Example 23 cis-4-Oxacyclohexane-l,l-dicarboxylato-2,2-­ dimethyl-l,4-butanediamine platinum (Compound No. 23) A compound No. 23 was obtained as white crystals in the same manner as in Example 20 except that the solu­ tion of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water was replaced by a solution obtained by dissolving 6l6 mg of 4-oxacyclohexane-l,l-dicarboxylic acid in 6.90 ml of l N aqueous sodium hydroxide solution. Yield: 326 mg Elementary analysis Calculated (%): C 32.30, H 5.00, N 5.79, Pt 40.35 Found (%): C 33.ll, H 4.97, N 6.0l, Pt 39.8 FAB-MS: (M + H)⁺ = 483 Example 24 cis-Dimethylmalonato-2,2-dimethyl-l,4-­ butanediamine platinum (Compound No. 24) A compound No. 24 was obtained as white crystals in the same manner as in Example 20 except that the solu­ tion of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water was replaced by a solution obtained by dissolving 467 mg of dimethylmalonic acid in 6.90 ml of l N aqueous sodium hydroxide solution. Yield: 407 mg Elementary analysis Calculated (%): C 29.93, H 5.02, N 6.35, Pt 44.20 Found (%): C 30.l4, H 5.28, N 6.l9, Pt 43.9 FAB-MS: (M + H)⁺ = 44l Example 25 cis-Dichloro-l,l-dimethyl-l,4-butanediamine platinum (Compound No. 25) In Example l, 2.l2 g of l,4-butanediamine was replaced by 2.80 g of l,l-dimethyl-l,4-butanediamine and there were obtained l0.62 g (yield: 78.0%) of reddish brown crystals of cis-diiodo-l,l-dimethyl-l,4-butane­ diamine platinum. In the same manner as in Example l except that l g of this product, 589 mg of silver nitrate and 620 mg of sodium chloride were used, a compound No. 25 was obtained as yellow crystals. Yield: 264 mg Elementary analysis Calculated (%): C l8.86, H 4.22, N 7.33, Pt 5l.04 Found (%): C l8.77, H 4.33, N 7.58, Pt 50.7 FAB-MS: (M + H)⁺ = 38l Example 26 cis-Oxalato-l,l-dimethyl-l,4-butanediamine platinum (Compound No. 26) In Example 25, the solution of 620 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water. The mixture resulting from addition of this solution was stirred for 2 hours at 60°C. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. 26. Yield: 433 mg Elementary analysis Calculated (%): C 24.06, H 4.04, N 7.02, Pt 48.85 Found (%): C 24.3l, H 4.22, N 7.0l, Pt 49.2 FAB-MS: (M + H)⁺ = 399 Example 27 cis-Cyclobutane-l,l-dicarboxylato-l,l-dimethyl-­ l,4-butanediamine platinum (Compound No. 27) A compound No. 27 was obtained as white crystals in the same manner as in Example 26 except that the solu­ tion of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water was replaced by a solution obtained by dissolving 5l0 mg of cyclobutante-l,l-dicarboxylic acid in 6.90 mg of l N aqueous sodium hydroxide solution. Yield: 207 mg Elementary analysis Calculated (%): C 3l.79, H 4.89, N 6.l8, Pt 43.03 Found (%): C 32.02, H 5.ll, N 6.0l, Pt 44.2 FAB-MS: (M + H)⁺ = 453 Example 28 cis-Dimethylmalonato-l,l-dimethyl-l,4-butane­ diamine platinum (Compound No. 28) A compound No. 28 was obtained as white crystals in the same manner as in Example 27 except that 5l0 mg of cyclobutane-l,l-dicarboxylic acid was replaced by 467 mg of dimethylmalonic acid. Yield: 337 mg Elementary analysis Calculated (%): C 29.93, H 5.02, N 6.35, Pt 44.20 Found (%): C 30.22, H 5.36, N 6.l0, Pt 43.4 FAB-MS: (M + H)⁺ = 44l Example 29 cis-Dichloro-2-ethyl-l,4-butanediamine platinum (Compound No. 29) In Example l, 2.l2 g of l,4-butanediamine was replaced by 2.80 g of 2-ethyl-l,4-butanediamine and there were obtained l0.32 g (yield: 75.8%) of reddish brown crystals of cis-diiodo-2-ethyl-l,4-butanediamine platinum. In the same manner as in Example l except that l g of this product, 589 mg of silver nitrate and 620 mg of sodium chloride were used, a compound No. 29 was obtained as yellow crystals. Yield: 257 mg Elementary analysis Calculated (%): C l8.86, H 4.22, N 7.33, Pt 5l.04 Found (%): C l9.00, H 4.35, N 7.l6, Pt 5l.0 FAB-MS: (M + H)⁺ = 38l Example 30 cis-Oxalato-2-ethyl-l,4-butanediamine platinum (Compound No. 30) In Example 29, the solution of 620 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water. The mixture resulting from addition of this solution was stirred for 2 hours at 60°C. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. 30. Yield: 428 mg Elementary analysis Calculated (%): C 24.06, H 4.04, N 7.02, Pt 48.85 Found (%): C 24.33, H 4.l7, N 6.96, Pt 48.5 FAB-MS: (M + H)⁺ = 399 Example 3l cis-Malonato-2-ethyl-l,4-butanediamine platinum (Compound No. 3l) A compound No. 3l was obtained in the same manner as in Example 30 except that the solution of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water was replaced by a solution obtained by dissolving 368 mg of molonic acid in 6.90 ml of l N aqueous sodium hydroxide solution. Yield: 280 mg Elementary analysis Calculated (%): C 26.l5, H 4.39, N 6.78, Pt 47.20 Found (%): C 26.53, H 4.50, N 6.59, Pt 46.l FAB-MS: (M + H)⁺ = 4l3 Example 32 cis-Cyclobutane-l,l-dicarboxylato-2-ethyl-l,4-­ butanediamine platinum (Compound No. 32) A compound No. 32 was obtained in the same manner as in Example 3l except that 368 mg of malonic acid was replaced by 5l0 mg of cyclobutane-l,l-dicarboxylic acis. Yield: 45l mg Elementary analysis Calculated (%): C 3l.79, H 4.89, N 6.l8, Pt 43.03 Found (%): C 3l.5l, H 4.67, N 6.22, Pt 42.l FAB-MS: (M + H)⁺ = 453 Example 33 cis-Dimethylmalonato-2-ethyl-l,4-butanediamine platinum (Compound No. 33) A compound No. 33 was obtained in the same manner as in Example 3l except that 368 mg of malonic acid was replaced by 467 mg of dimethylmalonic acid. Yield: 36l mg Elementary analysis Calculated (%): C 29.93, H 5.02, N 6.35, Pt 44.20 Found (%): C 30.l4, H 5.l8, N 6.l9, Pt 45.2 FAB-MS: (M + H)⁺ = 44l The physical characteristics of the compounds of the present invention are shown in Table l. In view of the fact that cis-Platin has solu­ bility of about l.2 mg/ml in physiological saline solu­ tion, the present compounds apparently have high solu­ bility in water. In addition, the present compounds are dissolved in water quickly. Therefore, when used as an injection, the crystals of the present compounds can be dissolved in water prior to administration and the resulting aqueous solutions can be administered immediately after dissolution. Next, the antitumor activities of the present compounds will be described by way of Experimental Examples. Experimental Example l Growth inhibition test on cultured mouse leukemia Ll2l0 cells (Test method) Mouse leukemia Ll2l0 cells were cultured in a RPMI l640 medium containing l0% of fetal calf serum. Inhibition percentage (%) of growth was calculated from the numbers of cells in the cases of addition and no addition of each compound, and IC₅₀ value (a concentra­ tion at which growth was inhibited by 50%) was obtained from a graph prepared by plotting a concentration of compound and the inhibition percentage on a logarithmic probability paper. The results are shown in Table 2. As is obvious from Table 2, the compounds of the present invention show an inhibition activity on the growth of cancer cells at a low concentration. The present compounds show an excellent inhibition activity also on the growth of cis-Platin resistant tumor cells which have acquired a resistance to cis-Platin as a result of its administration. An experimental example on this activity will be described on the compound No. l5 as an example. Experimental Example 2 Growth inhibition test on cis-­ Platin resistant tumor cells (Test method) l × l0⁵ mouse leukemia Ll2l0 cells or l × l0⁵ mouse leukemia P388 cells were inoculated into the abdominal cavities of CDF₁ female mouse. After 2 days from the inoculation, 6 mg/kg of cis-Platin was administered to them intraperitoneally. After 5 days, their tumor cells were inoculated to the abdominal cavities of other CDF₁ female mouse, and the same treat­ ment was applied. By repeating this procedure, cis-­ Platin resistant tumor cells were obtained. Using the tumor cells thus obtained, test for growth inhibition activity was conducted in the same manner as in Experimental Example l, whereby IC₅₀ for cis-Platin resistant tumor cells (hereinafter referred to as IC₅₀R) was obtained. Then, the ratio of this IC₅₀R to IC₅₀ for tumor cells having no cis-Platin resistance, namely, IC₅₀R/IC₅₀ was calculated. The results are shown in Table 3. As is obvious from Table 3, the present compounds show an inhibition activity also on the growth of cis-­ Platin resistant tumor cells, at a low concentration. Experimental Example 3 Antitumor activity test on mouse leukemia Ll2l0 in vivo (Test method) l × l0⁵ mouse leukemia Ll2l0 cells were inoculated into the abdominal cavities of 6-week-old female CDF₁ mice. From the next day, a compound was administered to them intra­ peritoneally once a day for 5 consecutive days. Mice of compound-non-treated group (control group) were administered with physiological saline solution in the same manner. The average survival times of the compound-treated group and the control group (abbreviated as T and C, respectively) were measured and T/C percentage (T/C × l00) was calculated from the following equation. When any mouse died during the test due to the acute toxicity of the compound administered, 50% lethal dose (LD₅₀) was calculated according to the conventional method. The results are shown in Table 4. In Table 4, max (T/C) means the maximum value of T/C and optimum dose (opt. dose) means an administration amount giving the max (T/C), namely, an optimum administration amount. As is obvious from Table 4, the compounds of the present invention have a life prolongation effect for mice inoculated with mouse leukemia Ll2l0 cells. The compounds of the present invention have life prolongation effects also for mice inoculated with tumor cells other than mouse leukemia Ll2l0 cells. These effects will be explained in Experimental Example 4 on the compound No. l5 as an example. Experimental Example 4 Antitumor activity test on various tumors in vivo (Test method) l × l0⁶ mouse leukemia P388 cells were in­ oculated into the abdominal cavities of 6-week-old female CDF₁ mice, and from the next day a compound No. l5 was administered to them intraperitoneally once a day for 5 consecutive days. Separately, l × l0⁶ mouse lung cancer Lewis lung carcinoma (LL) cells were inoculated into the abdominal cavities of male BDF₁ mice, and from the next day a compound No. l5 was administered to them intraperitoneally once a day for 5 consecutive days. Separately, l × l0⁶ mouse fibrosarcoma M5076 cells were inoculated into the body sides of female C57BL/6 mice subcutaneously, and from the next day a compound No. l5 was administered to them intraperitoneally. Separately, l × l0⁶ mouse colon cancer (colon 26) cells were inoculated into the abdominal cavities of female CDF₁ mice, and from the next day a compound No. l5 was administered to them intraperitoneally. To respective control groups (compound-non-treated groups), physiological saline solution was administered. From the survival times of the compound-treated group and the control group, respective median values (median survival times) were calcualted. Using these values, T/C percentage was calculated from the following equation. The results are shown in Table 5. As is obvious from Table 5, the compounds of the present invention have a striking life prolongation effect for mice inoculated with various tumor cells. Next, the renal toxicity of the present compounds will be described by way of an Experimental Example. Experimental Example 5 Test for renal toxicity (Test method) A compound was administered one time to 6-week-­ old male CDF₁ mice intraperitoneally. After 4 days, their blood was collected for measurement of blood urea nitrogen concentration (BUN value). The results are shown in Table 6.The optimum dose of cis-Platin was 4 mg/kg according to the test method of Example 3, but in the above renal toxicity test, a BUN value far higher than the normal value (30 mg/dl or lower) is seen even when cis-Platin was administered in an amount of four times the optimum dose. Based on this fact, as shown in Table 6, the administration amount of the present compound employed in this Experimental Example was 4 times the optimum dose obtained in Experimental Example 3, or more. In Table 6, body weight ratio is a ratio of body weight after 4 days from administration to body weight of administration day. As is obvious from Table 6, the BUN value obtained when the present compound is administered is very lower than the value obtained when commercially available cis-­ Platin is administered, and is close to the value obtained when physiological saline solution is administered. This indicates that the present compounds have very low renal toxicity. Accordingly, the present compounds can be used as an antitumor agent of very low renal toxicity. In view of this characteristics and high solubility in water, the present compounds, when intravenously injected, can be applied not in continuous administration but in bolus administration. Some of the present compounds have, as a ligand, a diamine having an asymmetric carbon atom. Such an amine was subjected to optical resolution to obtain its optical isomers. Using these isomers as a ligand, respective complexes were synthesized and tested. These syntheses and tests will be described on the compound No. l5 as examples, by way of Examples and Experimental Examples. Example 34 R-2-methyl-l,4-butanediamine 40 g of R-3-methyladipic acid was added to a mixture of 200 g of concentrated sulfuric acid and 320 ml of benzene. The mixture was heated to 45°C using a water bath to dissolve 3-methyladipic acid. To this solution was added 56 g of sodium azide gradually, and the mixture was subjected to reaction at 45° to 50°C. After the completion of the addition, stirring was continued for l0 minutes. Then, a saturated solution containing 200 g of sodium hydroxide was added dropwise. The resulting sodium sulfate precipitate was removed by filtration and the benzene phase in the filtrate was separated. The water phase of the filtrate was extracted with 500 ml of benzene, with 500 ml of ether and lastly with 500 ml of chloroform four times. All the extracts were mixed together and dehydrated with anhydrous sodium sulfate. Sodium sulfate was removed by filtration and the filtrate was concentrated using a rotary evaporator. The concentrate was subjected to vacuum distillation to obtain R-2-methyl-l,4-butanediamine. Yield: 6.92 g (yield: 27.l%) Boiling point: 83°C/30 mmHg Purity: 99.3% Optical purity: l00% In this Example and the following Example, purity and optical purity were determined according to methods such as gas chromatography, optical rotation measurement and the like. Example 35 Isolation of optical isomers of 2-methyl-l,4-­ butanediamine by optical resolution 2-methyl-l,4-butanediamine was subjected to optical resolution by converting it into a salt with dibenzoyltartaric acid and recrystallizing the salt (the two optical isomers have different solubilities). For obtaining R-2-methyl-l,4-butanediamine, (-)-dibenzoyl­ tartaric acid was used, and for obtaining S-2-methyl-­ l,4-butanediamine, (+)-dibenzoyltartaric acid was used. The resolution yields, purities and optical purities of the two isomers of 2-methyl-l,4-butanediamine are shown in Table 7. Using the optical isomers obtained in Examples 34 and 35 and in the same manner as in Example l5, there were obtained cis-cyclobutane-l,l-dicarboxylato-­ R-2-methyl-l,4-butanediamine platinum (compound No. l5R) and cis-cyclobutane-l,l-dicarboxylato-S-2-methyl-l,4-­ butanediamine platinum (compound No. l5S). Table 8 shows the synthesis yields and elementary analysis of these complexes when synthesized from potassium tetrachloro­ platinate (II), and Table 9 shows their physical pro­ perties. The (M + H)⁺ values of the complexes when measured by means of FAB-MS were both 439. The optical isomers l5R and l5S were subjected to the same tests as in Experimental Example l and Experimental Example 3. The results are shown in Table l0. The optical isomers l5R and l5S were also subject­ ed to the same test as in Experimental Example 4. The results are shown in Table ll. The optical isomers l5R and l5S were subjected to the same renal toxicity test as in Experimental Example 5. The results are shown in Table l2. The administration dose of each compound was four times the optimum dose shown in Table l0. As is obvious from the above experimental results, both l5R and l5S have high solubility in water, show excellent antitumor activities on various tumor cells and have very low renal toxicity. Example 36 (Compound No. 5) In Example 4, the solution of 636 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution of 343 mg of oxalic acid dihydrate dissolved in 5 ml of water. The mixture resulting from addition of this solution was stirred for 24 hours at 40°C. The reaction mixture was concentrated to 5 ml and then cooled to 0°C. The resulting white crystals were collected by filtration, washed with a small amount of water of 0°C and then with ethanol, and dried under vacuum to obtain a compound No. 5. The compound had the same analysis values as the compound No. 5 of Example 5. Example 37 (Compound No. 4) In Example 4, the solution of 604 mg of silver nitrate dissolved in l0 ml of water was replaced by a solution of 560 mg of silver sulfate dissolved in l50 ml of water. The mixture resulting from addition of this solution was stirred for 20 minutes at 80°C. The sub­ sequent procedure was same as in Example 4, whereby a compound No. 4 was obtained as yellow crystals. The compound had the same analysis value as the compound No. 4 of Example 4. The compounds of the present invention show an growth inhibition activity on the tumor cells at low concent­ rations and accordingly have a very excellent antitumor effect against various kinds of tumor. The present compounds have high solubility in water and are quickly dissolved in water. The present compounds have low renal toxicity and low vomitting toxicity. Further, the present compounds are mild with respect to bone marrow toxicity which is generally seen with the conventional platinum complex antitumor agents; that is, the decrease in the number of white blood cells occurs mainly and their toxicity to platelets is very slight. Furthermore, recovery to normal conditions is very rapid and accordingly control is easy when the present compounds are used as an antitumor agent. Based on these facts, the present compounds can be used as an excellent antitumor agent. Moreover, the present compounds are stable in air at room temperature, thus requiring no low temperature storage.

Claims: 1. A diamine platinum (II) complex represented by the general formula [wherein R₁, R₂, R₃ and R₄ are each a hydrogen atom or a lower alkyl group; and two X's are each a halogen atom or jointly form a group represented by (wherein R₅ and R₆ are each a hydrogen atom or a lower alkyl group) or a group represented by (wherein m is l or 2)]. 2. A diamine platinum (II) complex according to Claim l, wherein R₁ and R₂ are each a hydrogen atom. 3. A diamine platinum (II) complex according to Claim l or 2, wherein two X's jointly form a group repre­ sented by (wherein R₅ and R₆ are each a hydrogen atom or a lower alkyl group). 4. A diamine platinum (II) complex according to Claim l or 2, wherein two X's jointly form a group repre­ sented by 5. cis-Cyclobutane-l,l-dicarboxylato-l,4-butane­ diamine platinum. 6. cis-Malonato-2-methyl-l,4-butanediamine platinum. 7. cis-Cyclobutane-l,l-dicarboxylato-2-methyl-l,4-­ butanediamine platinum. 8. cis-Dimethylmalonato-2-methyl-l,4-butanediamine platinum. 9. cis-Ethylmalonato-2-methyl-l,4-butanediamine platinum. l0. cis-Malonato-2-ethyl-l,4-butanediamine platinum. 11. cis-Cyclobutane-l,l-dicarboxylato-2-ethyl-l,4-­ butanediamine platinum. 12. cis-Dimethylmalonato-2-ethyl-l,4-butanediamine platinum. 13. cis-Cyclobutane-l,l-dicarboxylato-R-2-methyl-­ l,4-butanediamine platinum. 14. cis-Cyclobutane-l,l-dicarboxylato-S-2-methyl-­ l,4-butanediamine platinum. 15. A process for preparing a diamine platinum II complex as defined in any one of the preceding claims which comprises reacting a diamine of the general formula: with a halide of formula M₂Pt(hal)₄ where R¹, R², R³ and R⁴ are as defined in any one of the preceding claims, M₂ is a group capable of becoming a monovalent cation and hal is halogen, to form a dihalo complex of the formula: and, optionally, reacting the dihalo complex with silver ions in the presence of water to convert it to a diaqua complex which is then reacted with a dicarboxylic acid of formula: where R⁵, R⁶ and m are as defined in any one of the preceding claims. 16. A pharmaceutical composition comprising a compound according to any one of claims l to l4 together with a pharmaceutically acceptable carrier or diluent. 17. A compound according to any one of claims l to l4 for use in a method for treatment of the human or animal body by surgery or therapy or in a method of diagnosis practised on the human or animal body. 18. A compound according to claim l7 for use in the treatment of tumours.

Inventors: HAYAMI, HIROSHI, KURODA, YASUO, NOWATARI, HIROYOSHI, TAKAHASHI, KATSUTOSHI, YODA, SUMIO
Applicants: NIPPON KAYAKU KABUSHIKI KAISHA
Application year: 1986
Main classification: C07F15
IPC codes: C07F15