Abstract:
A diamine platinum (II) complex represented by the general formula ##STR1## [wherein R 1 , R 2 , R 3  and R 4  are each a hydrogen atom or a lower alkyl group; and two X&#39;s are each a halogen atom or jointly form a group represented by ##STR2## (wherein R 5  and R 6  are each a hydrogen atom or a lower alkyl group) or a group represented by ##STR3## (wherein m is 1 or 2)].

Description:
This application is a division of application Ser. No. 087,045, now U.S. Pat. No. 4,864,043, filed Aug. 19, 1987, which is a continuation of application Ser. No. 893,108, filed Aug. 4, 1986, now U.S. Pat. No. 4,737,589, issued Apr. 12, 1988. 
    
    
     BACKGROUND OF THE INVENTION 
     1. 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 
     
         H.sub.2 N--C.sub.n R.sub.2n --NH.sub.2                     (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 1 to 3). [e.g. Japanese Patent Application Kokai (Laid-Open) No. 156416/1982 or 103192/1981]. 
     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 1,4-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 1,4-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) ##STR4## [wherein R 1 , R 2 , R 3  and R 4  are each a hydrogen atom or a lower alkyl group; and two X&#39;s are each a halogen atom or jointly form a group represented by ##STR5## (wherein R 5  and R 6  are each a hydrogen atom or a lower alkyl group) or a group represented by ##STR6## (wherein m is 1 or 2)]. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the above general formula (II), the lower alkyls represented by R 1 , R 2 , R 3 , R 4 , R 5  and R 6  include, for example, alkyl groups of 1 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&#39;s jointly form a group represented by ##STR7## Also preferable are those where R 1  and R 2  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-1,4-butanediamine platinum. 
     2. cis-Cyclobutane-1,1-dicarboxylato-1,4-butanediamine platinum. 
     3. cis-4-Oxacyclohexane-1,1-dicarboxylato-1,4-butanediamine platinum. 
     4. cis-Dichloro-1-methyl-1,4-butanediamine platinum. 
     5. cis-Oxalato-1-methyl-1,4-butanediamine platinum. 
     6. cis-Malonato-1-methyl-1,4-butanediamine platinum. 
     7. cis-Cyclobutane-1,1-dicarboxylato-1-methyl-1,4-butanediamine platinum. 
     8. cis-Dimethylmalonato-1-methyl-1,4-butanediamine platinum. 
     9. cis-Ethylmalonato-1-methyl-1,4-butanediamine platinum. 
     10. cis-Dichloro-1-ethyl-1,4-butanediamine platinum. 
     11. cis-Cyclobutane-1,1-dicarboxylato-1-ethyl-1,4-butanediamine platinum. 
     12. cis-4-Oxacyclohexane-1,1-dicarboxylato-1-ethyl-1,4-butanediamine platinum. 
     13. cis-Dichloro-2-methyl-1,4-butanediamine platinum. 
     14. cis-Malonato-2-methyl-1,4-butanediamine platinum. 
     15. cis-Cyclobutane-1,1-dicarboxylato-2-methyl-1,4- butanediamine platinum. 
     16. cis-4-Oxacyclohexane-1,1-dicarboxylato-2-methyl-1,4-butanediamine platinum. 
     17. cis-Dimethylmalonato-2-methyl-1,4-butanediamine platinum. 
     18. cis-Ethylmalonato-2-methyl-1,4-butanediamine platinum. 
     19. cis-Dichloro-2,2-dimethyl-1,4-butanediamine platinum. 
     20. cis-Oxalato-2,2-dimethyl-1,4-butanediamine platinum. 
     21. cis-Malonato-2,2-dimethyl-1,4-butanediamine platinum. 
     22. cis-Cyclobutane-1,1-dicarboxylato-2,2-dimethyl-1,4-butanediamine platinum. 
     23. cis-4-Oxacyclohexane-1,1-dicarboxylato-2,2-dimethyl-1,4-butanediamine platinum. 
     24. cis-Dimethylmalonato-2,2-dimethyl-1,4-butanediamine platinum. 
     25. cis-Dichloro-1,1-dimethyl-1,4-butanediamine platinum. 
     26. cis-Oxalato-1,1-dimethyl-1,4-butanediamine platinum. 
     27. cis-Cyclobutane-1,1-dicarboxylato-1,1-dimethyl-1,4-butanediamine platinum. 
     28. cis-Dimethylmalonato-1,1-dimethyl-1,4-butanediamine platinum. 
     29. cis-Dichloro-2-ethyl-1,4-butanediamine platinum. 
     30. cis-Oxalato-2-ethyl-1,4-butanediamine platinum. 
     31. cis-Malonato-2-ethyl-1,4-butanediamine platinum. 
     32. cis-Cyclobutane-1,1-dicarboxylato-2-ethyl-1,4-butanediamine platinum. 
     33. cis-Dimethylmalonato-2-ethyl-1,4-butanediamine platinum. 
     34. cis-Oxalato-2-isopropyl-1,4-butanediamine platinum. 
     35. cis-Dichloro-1,2-dimethyl-1,4-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, 193 (1970) 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 ##STR8## (wherein R 1 , R 2 , R 3  and R 4  have the same definitions as given previously, respectively) with 
     
         M.sub.2 Pt(Hal).sub.4 
    
     (wherein M is an atom capable of becoming a monovalent cation and Hal is a halogn atom) to obtain a dihalogenodiamine platinum complex represented by the general formula ##STR9## (wherein R 1 , R 2 , R 3  and R 4  and Hal have the same definitions 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. ##STR10## (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; R 1 , R 2 , R 3  and R 4  have the same definitions as given previously, respectively.) 
     As shown in the above reaction scheme, a tetrahalogenoplatinate 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 160 liters, particularly preferably 20 to 80 liters per 1 mole of the tetrahalogenoplatinate. The diamine is used in an amount of preferably 0.5 to 4 moles, particularly preferably 0.9 to 1.2 moles per 1 mole of the tetrahalogenoplatinate. This reaction is conducted at 0° to 100° 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 1 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). ##STR11## 
     The water for suspending the dihalogenodiamine complex (IIa) can be used in an appropriate amount but the amount preferably is 5 to 150 l per 1 mole of the complex (IIa). The amount of silver ion has no particular restriction but, from an economical standpoint, is preferred to be 0.5 to 6 equivalents per 1 equivalent of the dihalogenodiamine complex (IIa). In order to avoid an excessive addition, the amount particularly preferably is 1.9 to 2 equivalents per 1 equivalent of the dihalogenodiamine complex (IIa). The reaction is conducted at 0° to 100° 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 10 moles, particularly preferably 0.9 to 6 moles per 1 mole of the diaquacomplex (III). The reaction can be conducted at 0° to 100° C. but preferably is conducted at 40° to 90° C. to obtain a compound (IIb). ##STR12## (In the above, X&#39; 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 Pt 194 ) 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 temperature, 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 1 
     cis-Dichloro-1,4-butanediamine platinum (Compound No. 1) 
     10 g of potassium tetrachloroplatinate (II) was dissolved in 350 ml of water. Thereto was added a solution of 16 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, 2.12 g of 1,4-butanediamine was dissolved in 400 ml of water to obtain an aqueous 1,4-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 1,4-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 filtration 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-1,4-butanediamine platinum. 
     1 g of this product was suspended in 20 ml of water. Thereto was added a solution of 620 mg of silver nitrate dissolved in 10 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 10 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. 1. 
     Yield: 538 mg. 
     Elementary analysis 
     Calculated (%): C 13.57, H 3.42, N 7.91 Pt 55.09. 
     Found (%): C 13.44, H 3.56, N 8.04, Pt 54.8. 
     FAB-MS: (M+H) +  =353. 
     EXAMPLE 2 
     cis-Cyclobutane-1,1-dicarboxylato-1,4-butanediamine Platinum (Compound No. 2) 
     In Example 1, 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 1,1-cyclobutanedicarboxylic acid in 7.26 ml of 1 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 4.41, N 6.48, Pt 45.2. 
     FAB-MS: (M +H) +  =425. 
     EXAMPLE 3 
     cis-4-Oxacyclohexane-1,1-dicarboxylato-1,4-butanediamine platinum (Compound No. 3) 
     In Example 1, 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-1,1-dicarboxylic acid in 7.26 ml of 1 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 29.01, H 4.43, N 6.15, 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-1-methyl-1,4-butanediamine platinum (Compound No. 4) 
     In Example 1, 2.46 g of 1-methyl-1,4-butanediamine was used in place of 2.12 g of 1,4-butanediamine and there were obtained 9.64 g (yield 72.6%) of reddish brown crystals of cis-diiodo-1-methyl-1,4-butanediamine platinum. In the same manner as in Example 1 except that there were used 1 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 16.31, H 3.83, N 7.61, Pt 52.99. 
     Found (%): C 16.57, H 3.98, N 7.81, Pt 53.0. 
     FAB-MS: (M+H) +  =367. 
     EXAMPLE 5 
     cis-Oxalato-1-methyl-1,4-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 21.82, H 3.66, N 7.27, Pt 50.63. 
     Found (%): C 22.01, H 3.71, N 6.98, Pt 52.0. 
     FAB-MS: (M +H) =385. 
     EXAMPLE 6 
     cis-Malonato-1-methyl-1,4-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 1 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 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. 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-1,1-dicarboxylato-1-methyl-1,4-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-1,1dicarboxylic acid in 7.08 ml of 1 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 44.1. 
     FAB-MS: (M+H)  30  =439. 
     EXAMPLE 8 
     cis-Dimethylmalonato-1-methyl-1,4-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 1 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 28.11, H 4.72, N 6.55, Pt 45.65. 
     Found (%) C 28.40, H 4.91, N 6.30, Pt 46.4. FAB-MS: (M+H) +  =427. 
     EXAMPLE 9 
     cis-Ethylmalonato-1-methyl-1,4-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 1 N aqueous sodium hydroxide solution. The mixture resulting from addition of this solution was stirred for 2 hour 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. 9. 
     Yield: 575 mg. 
     Elementary analysis 
     Calculated (%): C 28.11, H 4.72, N 6.55, Pt 45.65. 
     Found (%): C27.88, H 4.65, N 6.48, Pt 46. 1. 
     FAB-MS: (M+H) +  =427. 
     EXAMPLE 10 
     cis-Dichloro-1-1-1,4-butanediamine platinum (Compound No. 10) 
     In Example 1, 2.12 g of 1,4-butanediamine was replaced by 2.80 g of 1-ehtyl-1,4-butanediamine and there where obtained 10.90 g (yield: 80.1%) of reddish brown crystals of cis-diiodo-1-ethyl-1,4-butanediamine platinum. In the same manner as in Example 1 except that 1 g of this product, 589 mg of silver nitrate and 620 mg of sodium chloride were used, a compound No. 10 was obtained as yellow crystals. 
     Yield: 394 mg. 
     Elementary analysis 
     Calculated (%): C 18.86, H 4.22, N 7.33, Pt 51.04. 
     Found (%): C 18.99, H 4.50, N 7.55, Pt 50.1. 
     FAB-MS: (M+H) +  =381. 
     EXAMPLE 11 
     cis-Cyclobutane-1,1-dicarboxylato-1-ethyl-1,4-butanediamine platinum (Compound No. 11) 
     In Example 10, the solution of 620 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 510 mg of cyclobutanedicarboxylic acid in 6.90 ml of 1 N aqueous sodium hydroxide solution. The mixtuer 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. 11. 
     Yield: 342 mg. 
     Elementary analysis 
     Calculated (%): C 31.79, H 4.89, N 6.18, Pt 43.03. 
     Found (%): C 31,53, H 4.71, N 6.36, Pt 42.6. 
     FAB-MS: (M+H) +  =453. 
     EXAMPLE 12 
     cis-4-Oxacyclohexane-1,1-dicarboxylato-1-ethyl-1,4-butanediamine platinum (Compound No. 12) 
     In Example 10, the solution of 620 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 616 mg of 4-oxacyclohexane-1,1-dicarboxylic acid in 7.08 ml of 1 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. 12. 
     Yield: 321 mg. 
     Elementary analysis 
     Calculated (%): C 32.30, H 5.00, N 5.79 Pt 40.35. 
     Found (%): C32.51, H 5.12, N 6.01, 39.2. 
     FAB-MS: (M+H) +  32 483. 
     EXAMPLE 13 
     cis-Dichloro-2-methyl-1,4-butanediamine platinum (Compound No. 13) 
     In Example 1, 2.12 g of 1,4-butanediamine was replaced by 2.46 g of 2-methyl-1,4-butanediamine and there were obtained 9.94 g (yield: 74.9%) of reddish brown crystals of cis-diiodo-2-methyl-1,4-butanediamine platinum. In the same manner as in Example 1 except that 1 g of this product, 604 mg of silver nitrate and 636 mg of sodium chloride were used, a compound No. 13 was obtained as yellow crystals. 
     Yield: 238 mg. 
     Elementary analysis 
     Calculated (%): C 16.31, H 3.83, N 7.61, Pt 52.99. 
     Found (%): C 16.15, H 3.70, N 7.44, Pt 53.1. 
     FAB-MS: (M+H) +  =367. 
     EXAMPLE 14 cis-Malonato-2-methyl-1,4-butanediamine platinum (Compound No. 14) 
     In Example 13, 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 1 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. 14. 
     Yield: 125 mg. 
     Elementary analysis 
     Calculated (%): C 24.06, H 4.04, N 7.02, Pt 48.85. 
     Found (%): C 24.22, H 3.99, N 7.41, Pt 49.4. 
     FAB-MS: (M+H) +  =399. 
     EXAMPLE 15 
     cis-Cyclobutane-1,1-dicarboxylato-2-methyl-1,4-butanediamine platinum (Compound No. 15) 
     A compound No. 15 was obtained as white crystals in the same manner as in Example 14 except that the solution obtained by dissolving 227 mg of malonic acid in 4.36 ml of 1 N aqueous sodium hydroxide solution was replaced by a solution obtained by dissolving 523 mg of cyclobutane-1,1-dicarboxylic acid in 7.29 ml of 1 N aqueous sodium hydroxide solution. 
     Yield 131 mg. 
     Elementary analysis 
     Calculated (%): C 30.07, H 4.59, N 6.38, Pt 44.40. 
     Found (%) C 30.20, H 4.31, N 6.15, Pt 44.5. 
     FAB-MS: (M+H) +  =439. 
     EXAMPLE 16 
     cis-4-Oxacyclohexane-1,1-dicarboxylato-2-methyl-1,4-butanediamine platinum (Compound No. 16) 
     A compound No. 16 was obtained in the same manner as in Example 15 except that 523 mg of cyclobutane-1,1-dicarboxylic acid was replaced by 632 mg of 4-oxacyclohexane-1,1-dicarboxylic acid. 
     Yield: 171 mg. 
     Elementary analysis Calculated (%): C 30.71, H 4.72, N 5.97, Pt 41.56. 
     Found (%): C 30.28, H 4.88, N 6.10, Pt 42.0. 
     FAB-MS: (M +H) 30  = 469. 
     EXAMPLE 17 
     cis-Dimethylmalonato-2-methyl-1,4-butanediamine platinum (Compound No. 17) 
     A compound No. 17 was obtained in the same manner as in Example 15 except that 523 mg of cyclobutane-1,1-dicarboxylic acid was replaced by 480 mg of dimethylmalonic acid. 
     Yield: 141 mg. 
     Elementary analysis 
     Calculated (%): C 28.11, 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 18 
     cis-Ethylmalonato-2-methyl-1,4-butanediamine platinum (Compound No. 18) 
     A compound No. 18 was obtained in the same manner as in Example 15 except that 523 mg of cyclobutane1,1-dicarboxylic acid was replaced by 480 mg of ethylmalonic acid. 
     Yield: 124 mg. 
     Elementary analysis 
     Calculated (%): C 28.11, H 4.72, N 6.56, Pt 45.65. Found (%) C 27.60, H 4.91, N 6.10, Pt 45.2. 
     FAB-MS: (M+H) 30  =427. 
     EXAMPLE 19 
     cis-Dichloro-2,2-dimethyl-1,4-butanediamine platinum (Compound No. 19) 
     In Example 1, 2.12 g of 1,4-butanediamine was replaced by 2.80 g of 2,2-dimethyl-1,4-butanediamine and there were obtained 11.20 g (yield: 82.3%) of yellowish brown crystals of cis-diiodo-2,2-dimethyl-1,4-butanediamine platinum. In the same manner as in Example 1 except that 1 g of this product, 589 mg of silver nitrate and 620 mg of sodium chloride were used, a compound No. 19 was obtained as yellow crystals. 
     Yield: 283 mg. 
     Elementary analysis 
     Calculated (%): C 18.86, H 4.22, N 7.33, Pt 51.04. 
     Found (%): C 19.12, H 4.03, N 7.01, Pt 50.8. 
     FAB-MS: (M+H) +  =381. 
     EXAMPLE 20 
     cis-Oxalato-2,2-dimethyl-1,4-butanediamine platinum (Compound No. 20) 
     In Example 19, 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 4.11, N 6.86, Pt 49.3. 
     FAB-MS: (M+H) +  =399. 
     EXAMPLE 21 
     cis-Malonato-2,2-dimethyl-1,4-butanediamine platinum (Compound No. 21) 
     A compound No. 21 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 1 N aqueous sodium hydroxide solution. 
     Yield 331 mg. 
     Elementary analysis 
     Calculated (%): C 26.15, H 4.39, N 6.78, Pt 47.20. 
     Found (%): C 26.51, H 4.55, N 6.41, Pt 46.1. 
     FAB-MS: (M +H) +=  413. 
     EXAMPLE 22 
     cis-Cyclobutane-1,1-dicarboxylato-2,2-dimethyl-1,4-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 solution of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water was replaced by a solution obtained by dissolving 510 mg of cyclobutane-1,1-dicarboxylic acid in 6.90 ml of 1 N aqueous sodium hydroxide solution. 
     Yield: 375 mg. 
     Elementary analysis 
     Calculated (%): C 31.79, H 4.89, N 6.18, Pt 43.03. 
     Found (%) C 31.81, H 5.01, N 6.36, Pt 43.2. 
     FAB-MS: (M +H)+=453. 
     EXAMPLE 23 
     cis-4-Oxacyclohexane-1,1-dicarboxylato-2,2-dimethyl-1,4-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 solution of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water was replaced by a solution obtained by dissolving 616 mg of 4-oxacyclohexane-1,1-dicarboxylic acid in 6.90 ml of 1 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 33.11, H 4.97, N 6.01, Pt 39.8. 
     FAB-MS: (M +H) +=  483. 
     EXAMPLE 24 
     cis-Dimethylmalonato-2,2-dimethyl-1,4-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 solution 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 1 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 30.14, H 5.28, , N 6.19, Pt 43.9. 
     FAB-MS: (M+H) +  =441. 
     EXAMPLE 25 
     cis-Dichloro-1,1-dimethyl-1,4-butanediamine platinum (Compound No. 25) In Example 1, 2.12 g of 1,4-butanediamine was replaced by 2.80 g of 1,1-dimethyl-1,4-butanediamine and there were obtained 10.62 g (yield: 78.0%) of reddish brown crystals of cis-diiodo-1,1-dimethyl-1,4-butanediamine platinum. In the same manner as in Example 1 except that 1 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 18.86, H 4.22, N 7.33, Pt 51.04. 
     Found (%): C 18.77, H 4.33, N 7.58, Pt 50.7. 
     FAB-MS: (M+H) +  =381. 
     EXAMPLE 26 
     cis-Oxalato-1,1-dimethyl-1,4-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 24.31, H 4.22, N 7.01, Pt 49.2. 
     FAB-MS: (M +H) +=  399. 
     EXAMPLE 27 
     cis-Cyclobutane-1,1-dicarboxylato-1,1-dimethyl-1,4-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 solution of 652 mg of potassium oxalate monohydrate dissolved in 5 ml of water was replaced by a solution obtained by dissolving 510 mg of cyclobutante-1,1-dicarboxylic acid in 6.9 ml of 1 N aqueous sodium hydroxide solution. 
     Yield: 207 mg. 
     Elementary analysis 
     Calculated (%): C 31.79, H 4.89, N 6.18, Pt 43.03. 
     Found (%): C 32.02, H 5.11, N 6.01, Pt 44.2. 
     FAB-MS: (M+H) +  =453. 
     EXAMPLE 28 
     cis-Dimethylmalonato-1,1-dimethyl-1,4-butanediamine platinum (Compound No. 28) 
     A compound No. 28 was obtained as white crystals in the same manner as in 
     EXAMPLE 27 except that 510 mg of cyclobutane-1,1-dicarboxylic acid was replaced by 467 mg of dimethylmalonic acid. 
     Yield: 337 mg. 
     Calculated (%): C 29.93, H 5.02, N 6.35, Pt 44.20. 
     Found (%): C 30.22, H 5.36, N 6.10, Pt 43.4. 
     FAB-MS: (M+H) +  =441. 
     EXAMPLE 29 
     cis-Dichloro-2-ethyl-1,4-butanediamine platinum (Compound No. 29) 
     In Example 1, 2.12 g of 1,4-butanediamine was replaced by 2.80 g of 2-ethyl-1,4-butanediamine and there were obtained 10.32 g (yield: 75.8%) of reddish brown crystals of cis-diiodo-2-ethyl-1,4-butanediamine platinum. In the same manner as in Example 1 except that 1 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 18.86, H 4.22, N 7.33, Pt 51.04. 
     Found (%): C 19.00, H 4.35, N 7.16, Pt 51.0. 
     FAB-MS: (M +H) +=  381. 
     EXAMPLE 30 
     cis-Oxalato-2-ethyl-1,4-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 4.17, N 6.96, Pt 48.5. 
     FAB-MS: (M+H) +  =399. 
     EXAMPLE 31 
     cis-Malonato-2-ethyl-1,4-butanediamine platinum (Compound No. 31) 
     A compound No. 31 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 1 N aqueous sodium hydroxide solution. 
     Yield: 280 mg. 
     Elementary analysis 
     Calculated (%): C 26.15, H 4.39, N 6.78, Pt 47.20. 
     Found (%): C 26.53, H 4.50, N 6.59, Pt 46.1. 
     FAB-MS: (M+H) +  =413. 
     EXAMPLE 32 
     cis-Cyclobutane-1,1-dicarboxylato-2-ethyl-1,4-butanediamine platinum (Compound No. 32) 
     A compound No. 32 was obtained in the same manner as in Example 31 except that 368 mg of malonic acid was replaced by 510 mg of cyclobutane-1,1-dicarboxylic acis. 
     Yield: 451 mg. 
     Elementary analysis 
     Calculated (%): C 31.79, H 4.89, N 6.18, Pt 43.03. 
     Found (%): C 31.51, H 4.67, N 6.22, Pt 42.1. 
     FAB-MS: (M+H) =+  453. 
     EXAMPLE 33 
     cis-Dimethylmalonato-2-ethyl-1,4-butanediamine platinum (Compound No. 33) 
     A compound No. 33 was obtained in the same manner as in Example 31 except that 368 mg of malonic acid was replaced by 467 mg of dimethylmalonic acid. 
     Yield: 361 mg. 
     Elementary analysis 
     Calculated (%): C 29.93, H 5.02, N 6.35, Pt 44.20. 
     Found (%): C 30.14, H 5.18, N 6.19, Pt 45.2. 
     FAB-MS: (M+H) +  =441. 
     The physical characteristics of the compounds of the present invention are shown in Table 1. 
     
                       TABLE 1______________________________________   SolubilityCompound  in water   IR absorption spectrum (cm.sup.-1)No.       (mg/ml)    N--H       C═O______________________________________1         &gt;2*        3250-3150  --2         &gt;5         3210-3130  1650-16103         &gt;10        3230-3120  1670-16304         &gt;2*        3240-3150  --5         &gt;3         3220-3140  1700-16856         &gt;10        3260-3090  1640-16007         &gt;5         3220-3110  1660-16008         &gt;20        3230-3140  1640-15909         &gt;10        3250-3110  1630-159010        &gt;2*        3230-3120  --11        &gt;3         3210-3100  1650-160012        &gt;5         3230-3090  1680-162013        &gt;2*        3248-3225  --14        &gt;50        3200-3125  1730-161015        &gt;8         3200-3125  1700-162016        &gt;15        3200-3130  1690-161017        &gt;20        3250-3125  1680-164018        &gt;10        3190-3120  1710-162019        &gt;2*        3220-3130  --20        &gt;3         3260-3140  1690-166021        &gt;5         3190-3120  1680-161022        &gt;3         3220-3130  1620-160023        &gt;3         3230-3130  1650-159024        &gt;10        3250-3140  1640-159025        &gt;2*        3210-3130  --26        &gt;3         3220-3140  1700-166027        &gt;10        3220-3130  1640-160028        &gt;10        3240-3140  1640-159029        &gt;2*        3220-3130  --30        &gt;3         3240-3120  1690-166031        &gt;10        3230-3130  1680-160032        &gt;5         3220-3130  1630-159033        &gt;10        3240-3150  1650-1600______________________________________ *Solubility in physiological saline solution 
    
     In view of the fact that cis-Platin has solubility of about 1.2 mg/ml in physiological saline solution, the present compounds apparently have high solubility 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 1 
     Growth inhibition test on cultured mouse leukemia L1210 cells 
     (Test method) 
     Mouse leukemia L1210 cells were cultured in a RPMI 1640 medium containing 10% 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 IC 50  value (a concentration 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. 
     
                       TABLE 2______________________________________Compound No.   IC.sub.50 (μg/ml)______________________________________1              0.332              0.883              0.654              0.205              0.296              0.767              2.808              0.909              2.4010             0.3511             4.7012             1.0513             0.1014             0.7415             1.2016             0.4317             0.5018             0.8419             0.2020             0.3721             0.7222             2.2023             0.4424             0.7825             0.2526             0.3028             4.5029             0.0530             0.0631             0.6632             0.6733             0.23______________________________________ 
    
     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. 15 as an example. 
     EXPERIMENTAL EXAMPLE 2 
     Growth inhibition test on cis-Platin resistant tumor cells 
     (Test method) 
     1×10 5  mouse leukemia L1210 cells or 1×10 5  mouse leukemia P388 cells were inoculated into the abdominal cavities of CDF 1  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 CDF 1  female mouse, and the same treatment 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 1, whereby IC 50  for cis-Platin resistant tumor cells (hereinafter referred to as IC 50  R) was obtained. Then, the ratio of this IC 50  R to IC 50  for tumor cells having no cis-Platin resistance, namely, IC 50  R/IC 50  was calculated. 
     The results are shown in Table 3. 
     
                       TABLE 3______________________________________       IC.sub.50 R/IC.sub.50Compound      Tumor cell                   Tumor cellNo.           L1210     P388______________________________________Cis-Platin    11.4      10.715            3.19      3.26______________________________________ 
    
     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 L1210 in vivo 
     (Test method) 1×10 5  mouse leukemia L1210 cells were inoculated into the abdominal cavities of 6-week-old female CDF l  mice From the next day, a compound was administered to them intraperitoneally 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×100) was calculated from the following equation. ##EQU1## 
     When any mouse died during the test due to the acute toxicity of the compound administered, 50% lethal dose (LD 50 ) 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 namely, an optimum administration amount. 
     
                       TABLE 4______________________________________Compound                Opt. dose                            LD.sub.50No.       max (T/C)     (mg/kg)  (mg/kg)______________________________________1         203           2        4.82         182           32       48.03         132           8        8.44         225           2        2.45         273           4        6.06         359           32       48.07         176           64       --8         189           64       --9         222           64       96.010        210           4        6.011        139           64       --12        181           64       --13        187           2        4.214        346           32       --15        182           32       80.016        167           8        12.017        238           32       --18        264           16       24.019        359           4        6.020        272           8        12.021        301           32       48.022        320           128      --23        159           32       --24        253           64       --25        150           2        3.029        261           2        3.030        253           8        --32        275           32       --______________________________________ 
    
     As is obvious from Table 4, the compounds of the present invention have a life prolongation effect for mice inoculated with mouse leukemia L1210 cells. 
     The compounds of the present invention have life prolongation effects also for mice inoculated with tumor cells other than mouse leukemia L1210 cells. These effects will be explained in Experimental Example 4 on the compound No. 15 as an example. 
     EXPERIMENTAL EXAMPLE 4 
     Antitumor activity test on various tumors in vivo 
     (Test method) 
     1×10 6  mouse leukemia P388 cells were inoculated into the abdominal cavities of 6-week-old female CDF 1  mice, and from the next day a compound No. 15 was administered to them intraperitoneally once a day for 5 consecutive days. Separately, 1×10 6  mouse lung cancer Lewis lung carcinoma (LL) cells were inoculated into the abdominal cavities of male BDF l  mice, and from the next day a compound No. 15 was administered to them intraperitoneally once a day for 5 consecutive days. Separately, 1×10 6  mouse fibrosarcoma M5076 cells were inoculated into the body sides of female C57BL/6 mice subcutaneously, and from the next day a compound No. 15 was administered to them intraperitoneally. Separately, 1×10 6  mouse colon cancer (colon 26) cells were inoculated into the abdominal cavities of female CDF 1  mice, and from the next day a compound No. 15 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 calculated. Using these values, T/C percentage was calculated from the following equation. ##EQU2## 
     The results are shown in Table 5. 
     
                       TABLE 5______________________________________Antitumor activity of compoundNo. 15 on various tumor cellsTumor cell   Max (T/C) Opt. dose (mg/kg)______________________________________P388         260       32LL           222       32M5076        152       16Colon 26     198       32______________________________________ 
    
     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 CDF l  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 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. 
     
                       TABLE 6______________________________________       Administra- Body       tion amount weight  BUN valueCompound No.       (mg/kg)     ratio   (mg/dl)______________________________________Physiological       --          1.05    22.7salt solutioncis-Platin  16          0.72    92.91           8           0.83    11.42           128         0.73    16.24           8           0.75    28.45           16          0.76    12.96           128         0.75    24.67           256         0.85    13.18           256         0.71    25.410          16          0.74    21.311          256         1.09    23.212          256         0.94    16.813          20          0.74    22.614          128         0.72    15.915          240         0.74    19.817          128         0.73    16.718          64          0.74    19.619          16          0.76    15.720          32          0.75    13.521          128         0.76    16.722          512         0.74    14.423          128         0.89    15.024          256         0.79    19.725          8           0.79    16.829          8           0.72    18.130          32          0.87    18.232          128         0.74    19.7______________________________________ 
    
     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. 15 as examples, by way of Examples and Experimental Examples. 
     EXAMPLE 34 
     R-2-methyl-1,4-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 10 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-1,4-butanediamine. 
     Yield: 6.92 g (yield: 27.1%). 
     Boiling point: 83° C./30 mmHg. 
     Purity: 99.3%. 
     Optical purity: 100%. 
     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-1,4-butanediamine by optical resolution 2-methyl-1,4-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-1,4-butanediamine, (-)-dibenzoyltartaric acid was used, and for obtaining S-2-methyl1,4-butanediamine, (+)-dibenzoyltartaric acid was used. The resolution yields, purities and optical purities of the two isomers of 2-methyl-1,4-butanediamine are shown in Table 7. 
     
                       TABLE 7______________________________________   Resolution          Optical   yield       Purity  purity   (%)         (%)     (%)______________________________________R-isomer  57.8          100     98.6S-isomer  51.4          100     98.8______________________________________ 
    
     Using the optical isomers obtained in Examples 34 and 35 and in the same manner as in Example 15, there were obtained cis-cyclobutane-1,1-dicarboxylato-R- 2-methyl-1,4-butanediamine platinum (compound No. 15R) and cis-cyclobutane-1,1-dicarboxylato-S-2-methyl-1,4-butanediamine platinum (compound No. 15S). Table 8 shows the synthesis yields and elementary analysis of these complexes when synthesized from potassium tetrachloroplatinate (II), and Table 9 shows their physical properties. The (M+H) +   values of the complexes when measured by means of FAB-MS were both 439. 
     
                       TABLE 8______________________________________Compound Synthesis yield                Elementary analysis (%)No.      (%)         C       H     N     Pt______________________________________15R      24.6        29.98   4.43  6.22  44.815S      23.1        30.21   4.37  6.36  45.0______________________________________ 
    
     
                       TABLE 9______________________________________   Solubility in              IR absorption spectrumCompound  water        (cm.sup.-1)No.       (mg/ml)      N--H      C═O______________________________________15R       &gt;15          3200-3125 1700-162015S       &gt;15          3210-3130 1700-1620______________________________________ 
    
     The optical isomers 15R and 15S were subjected to the same tests as in Experimental Example 1 and Experimental Example 3. The results are shown in Table 10. 
     
                       TABLE 10______________________________________Compound  IC.sub.50  max     Opt. dose                                 LD.sub.50No.       (μg/ml) (T/C)   (mg/kg)  (mg/kg)______________________________________15R       0.78       189     32       33.615S       1.08       206     32       48.0______________________________________ 
    
     The optical isomers 15R and 15S were also subjected to the same test as in Experimental Example 4. The results are shown in Table 11. 
     
                       TABLE 11______________________________________Compound     Tumor     max     Opt. doseNo.          cell      (T/C)   (mg/kg)______________________________________15R          P388      253     2015R          LL        166     3015S          P388      253     4015S          LL        164     50______________________________________ 
    
     The optical isomers 15R and 15S were subjected to the same renal toxicity test as in Experimental Example 5. The results are shown in Table 12. The administration dose of each compound was four times the optimum dose in Table 10. 
     
                       TABLE 12______________________________________Compound Administration                 Body weight BUN valueNo.      amount (mg/kg)                 ratio       (mg/dl)______________________________________15R      128          0.71        10.615S      128          0.90        21.4______________________________________ 
    
     As is obvious from the above experimental results, both 15R and 15S 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 10 ml of water was replaced by a solution of 560 mg of silver sulfate dissolved in 150 ml of water. The mixture resulting from addition of this solution was stirred for 20 minutes at 80° C. The subsequent 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 concentrations 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.