Bis-dioxopiperazine derivatives, process for their preparation, antitumor agents comprising them and compositions containing them
BACKGROUND OF THE INVENTION 
     The present invention relates to novel bis-dioxopiperazine derivatives and non-toxic salts thereof, process for their preparation, antitumor agents comprising them and compositions containing them. 
     Bis-dioxopiperazine derivatives of the present invention are represented by the following general formula (I): ##STR2## wherein R represents an alkyl radical having 1 to 17 carbon atoms, a cycloalkyl radical having 3 to 7 carbon atoms, a lower alkyl radical having a substituent or substituents selected from the group consisting of halogeno, carboxy, alkoxycarbonyl having 2 to 5 carbon atoms, lower alkoxy, substituted or unsubstituted phenoxy, naphthyloxy, substituted or unsubstituted phenylthio, substituted or unsubstituted phenyl and naphthyl, a substituted or unsubstituted phenyl lower alkenyl radical, a substituted or unsubstituted phenyl radical, a naphthyl radical, a heterocyclic radical selected from the group consisting of pyridyl, furyl and thienyl, an alkoxy radical having 1 to 8 carbon atoms, a substituted or unsubstituted phenyl lower alkoxy radical, or a substituted or unsubstituted phenoxy radical. A substituent or substituents on R may be selected from the group consisting of lower alkyl, halogeno, lower alkoxy, acyloxy having 2 to 5 carbon atoms, methylenedioxy, carboxy, amino, methanesulfonylamino and nitro. The above-mentioned &#34;lower alkyl&#34;, &#34;lower alkoxy&#34; and &#34;lower alkenyl&#34; respectively refer to alkyl having 1 to 4 carbon atoms, alkoxy having 1 to 4 carbon atoms and alkenyl having 2 to 4 carbon atoms. 
     Several kinds of bis-dioxopiperazine derivatives have been already reported. Especially 1,2-bis(4-morpholinomethyl-3,5-dioxopiperazin-1-yl)ethane is known as an analogue of the compound which the present invention concerns and its clinical efficacy as an antitumor and radio-potentiative agent was already evaluated (see Abstract, 8th International Congress of Pharmacology p441, 1981). However the known compound had a problem on the preparation because it is extremely unstable in the protic polar solvents such as water, lower alcohol and so on. 
     Based on the attractive biological activities of the known bis-dioxopiperazine derivatives, we, the inventors further carried out the synthesis studies on these derivatives with the excellent activity and pharmaceutically advantageous property. We found that the aforementioned bis-dioxopiperazine derivatives of general formula (I) exhibit broader spectra of antitumor activities, antimetastatic activity, pharmaceutically advantageous stability in the protic polar solvents, and lower toxicity, thus accomplishing the present invention. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Bis-dioxopiperazine derivatives of the present invention are represented by the general formula (I) wherein R represents an alkyl radical having 1 to 17 carbon atoms, a cycloalkyl radical having 3 to 7 carbon atoms, a lower alkyl radical having a substituent or substituents selected from the group consisting of halogeno, carboxy, alkoxy-carbonyl having 2 to 5 carbon atoms, lower alkoxy, substituted or unsubstituted phenoxy, naphthyloxy, substituted or unsubstituted phenylthio, substituted or unsubstituted phenyl and naphthyl, a substituted or unsubstituted phenyl lower alkenyl radical, a substituted or unsubstituted phenyl radical, a naphthyl radical, a heterocyclic radical selected from the group consisting of pyridyl, furyl and thienyl, an alkoxy radical having 1 to 8 carbon atoms, a substituted or unsubstituted phenyl lower alkoxy radical, or a substituted or unsubstituted phenoxy radical. A substituent or substituents on R may be selected from the group consisting of lower alkyl, halogeno, lower alkoxy, acyloxy having 2 to 5 carbon atoms, methylenedioxy, carboxy, amino, methanesulfonylamino and nitro. The above-mentioned &#34;lower alkyl&#34;, &#34;lower alkoxy&#34; and &#34;lower alkenyl&#34; respectively refer to alkyl having 1 to 4 carbon atoms, alkoxy having 1 to 4 carbon atoms and alkenyl having 2 to 4 carbon atoms. The alkyl radical having 1 to 17 carbon atoms is selected from the group having a normal or branched carbon chain such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentadecyl, hexadecyl, heptadecyl, and so on. The cycloalkyl radical having 3 to 7 carbon atoms is selected from the group containing cyclopentyl, cyclohexyl, cycloheptyl and so on. The halogeno lower alkyl radical is selected from the group containing chloromethyl, bromomethyl, dichlocromethyl, bromoethyl and so on. The carboxy lower alkyl radical is selected from the group containing carboxyethyl, carboxyproply and so on. The lower alkyl radical substituted with alkyloxycarbonyl having 2 to 5 carbon atoms is selected from the group containing methoxycarbonylmethyl, methoxycarbonylethyl, ethoxycarbonylethyl, methoxycarbonylpropyl and so on. The lower alkoxy lower alkyl radical is selected from the group containing methoxymethyl, methoxyethyl, ethoxymethyl and so on. The substituted or unsubstituted phenoxy lower alkyl radical is selected from the group containing phenoxymethyl, phenoxy ethyl, p-chlorophenoxymethyl, 2,4-dichlorophenoxymethyl, 2,4,5-trichlorophenoxymethyl, 1-p-chlorophenoxy-1-methylethyl and so on. The naphthyloxy lower alkyl radical is selected from the group containing 2-naphthyloxymethyl, 2-naphthyloxyethyl and so on. The substituted or unsubstituted phenylthio lower alkyl radical is selected from the group containing phenylthiomethyl, p-bromophenylthiomethyl, p-fluorophenylthiomethyl and so on. The substituted or unsubstituted phenyl lower alkyl radical is selected from the group containing benzyl, phenethyl, o-chlorobenzyl, o-bromobenzyl, o-tolylmethyl, α-hydroxybenzyl and so on. The naphthyl lower alkyl radical is selected from the group containing 1-naphthylmethyl, 2-naphthylethyl and so on. The substituted or unsubstituted phenyl lower alkenyl radical is selected from the group containing styryl, cinnamyl, 3,4-dihydroxystyryl, p-methoxystyryl, 3,4-dimethoxystyryl, 3,4-diacetoxystyryl and so on. The substituted or unsubstituted phenyl radical is selected from the group containing phenyl, o-chlorophenyl, o-fluorophenyl, p-chlorophenyl, p-bromophenyl, o-tolyl, m-tolyl, o-methoxyphenyl, 3,4-dihydroxyphenyl, 3,4-diacetoxyphenyl, 3,4-methylenedioxyphenyl, p-nitrophenyl, p-cyanophenyl, p-aminophenyl, p-methanesulfonylaminophenyl, o-carboxyphenyl and so on. The naphthyl radical is selected from the group containing 1-naphthyl, 2-naphthyl and so on. The heterocyclic radical is selected from the group containing 2-pyridyl, 3-pyridyl, 4-pyridyl, 2-furyl, 3-furyl, 2-thienyl and so on. The alkoxy radical having 1 to 8 carbon atoms is selected from the group containing methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, 2-ethylhexyloxy and so on. The substituted or unsubstituted phenyl lower alkoxy radical is selected form the group containing benzloxy, p-nitrobenzyloxy, o-methoxybenzyloxy, phenethyloxy and so on. The substituted or unsubstituted phenoxy radical is selected from the group containing phenoxy, o-chlorophenoxy and so on. 
     The compounds according to the present invention are for example as follows: 
     1,2-bis(4-acetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-n-butyryloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-isovaleryloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-pivaloyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-palmitoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-stearoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-cyclohexylcarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-chloroacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-dichloroacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-bromoacetoxymethyl-3,5-dioxopiperazin-1yl)ethane; 
     1,2-bis(4-β-carboxypropionyloxymethyl-3,5-dioxopiperazin-1-yl)ethane or sodium salts thereof; 
     1,2-bis(4-β-methoxycarbonylpropionyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-methoxyacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-phenoxyacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-p-chlorophenoxyacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis[4-(2,4-dichlorophenoxyacetoxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis[4-(2,4,5-trichlorophenoxyacetoxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis[4-(2-p-chlorophenoxy-2-methylpropionyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis[4-(2-naphthyloxyacetoxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis(4-p-fluorophenylthioacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-p-bromophenylthioacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-phenylacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-o-chlorophenylacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-o-bromophenylacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-o-tolylacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-α-hydroxy-α-phenylacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis[4-(1-naphthylacetoxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis(4-cinnamoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis[4-(3,4-diacetoxycinnamoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis(4-p-methoxycinnamoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis[4-(3,4-dimethoxycinnamoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis(4-benzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-o-chlorobenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-o-fluorobenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-o-toluoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-m-toluoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-o-methoxybenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis[4-(3,4-diacetoxybenzoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis[4-(3,4-methylenedioxybenzoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis(4-o-carboxybenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-p-aminobenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-p-methanesulfonylaminobenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis[4-(1-naphthoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis[4-(2-pyridylcarbonyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis[4-(3-pyridylcarbonyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis[4-(2-thenoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis[4-(2-furoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis(4-methoxycarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-ethoxycarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-n-butoxycarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-isobutoxycarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis[4-(2-ethylhexyloxycarbonyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane; 
     1,2-bis(4-p-nitrobenzyloxycarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane; 
     1,2-bis(4-phenoxycarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     The compounds (I) of the present invention may form themselves into acid addition salts, e.g., hydrochloride, oxalate, p-toluenesulfonate, acetate and so on, as the nontoxic salts. 
     Process for the preparation of bis-dioxopiperazine derivatives of the general formula (I) comprises treatment of the compound shown as formula (II): ##STR3## with a reactive derivative such as a chloride or an anhydride of the compound shown as general formula (III): 
     
         RCOOH                                                      (III) 
    
     wherein R is as defined in the formula (I). 
     The chloride of the compound (III) may be selected from the group containing acetyl chloride, n-butyryl chloride, isovaleryl chloride, pivaloyl chloride, palmitoyl chloride, stearoyl chloride, cyclohexanecarbonyl chloride, chloroacetyl chloride, dichloroacetyl chloride, bromoacetyl chloride, methoxyacetyl chloride, phenoxyacetyl chloride, p-chlorophenoxyacetyl chloride, 2,4-dichlorophenoxyacetyl chloride, 2,4,5-trichlorophenoxyacetyl chloride, 2-p-chlorophenoxy-2-methylpropionyl chloride, 2-naphthyloxyacetyl chloride, p-bromophenylthioacetyl chloride, p-fluorophenylthioacetyl chloride, o-chlorophenylacetyl chloride, o-bromophenylacetyl chloride, α-chloroacetoxy-α-phenylacetyl chloride, 1-naphthylacetyl chloride, cinnamoyl chloride, 3,4-diacetoxycinnamoyl chloride, p-methoxycinnamoyl chloride, 3,4-dimethoxycinnamoyl chloride, benzoyl chloride, o-chlorobenzoyl chloride, o-fluorobenzoyl chloride, o-toluoyl chloride, m-toluoyl chloride, o-methoxybenzoyl chloride, 3,4-diacetoxybenzoyl chloride, 3,4-methylenedioxybenzoyl chloride, p-benzloxycarbonyl-aminobenzoyl chloride, 2-pyridylcarbonyl chloride, 3-pyridylcarbonyl chloride, 2-thenoyl chloride, 2-furoyl chloride, methyl chloroformate, ethyl chloroformate, n-butyl chloroformate, isobutyl chloroformate, 2-ethylhexyl chloroformate, p-nitrobenzyl chloroformate, phenyl chloroformate and so on, while the anhydride of the compound (III) may be selected from the group containing acetic anhydride, n-butyric anhydride, isobutyric anhydride, propionic anhydride, monochloroacetic anhydride, succinic anhydride, and so on. 
     The compound of the formula (II) which is the starting material in a process of the present invention is a novel compound and can be prepared easily by reacting 1,2-bis(3,5-dioxopiperazin-1-yl)ethane described in British Patent Specification No. 1234935, with formaldehyde. 
     In the process of preparing bis-dioxopiperazine derivatives which the present invention concerns, at least two equivalent molar amounts of chloride or anhydride of the compounds (III) should be used to one molar amount of the starting material of the formula (II). 
     The reaction temperature may range from -10° to 120° C., preferably from 0° to 80° C., and the reaction time may range from 1 to 24 hours. 
     As for the reaction solvent, an aprotic polar solvent for instance, DMF, acetonitrile, chloroform, dichloromethane, ethyl acetate, pyridine, lutidine, picoline, or their mixture may be used. The above reaction is performed preferably in the presence of the base such as pyridine, triethylamine and so on. 
     The compounds (I) of the present invention may be prepared by reacting the compound of the formula (II) with the compounds of the general formula (III) in the presence of the condensing agents such as 1-methyl-2-chloropyridinium iodide, 2-chloro-3-ethylbenzoxazorium tetrafluoroborate, dicyclohexylcarbodiimide and so on. 
     In this condensation reaction, at least two equivalent molar amount of the compound of the general formula (III) should be used to one molar amount of the compound of the general formula (II). 
     The reaction temperature may range from -30° to 100° C., preferably from 0° C. to room temperature and the reaction time may range from 1 to 24 hours which depends on reaction temperature. 
     As for the reaction solvent, an aprotic polar solvent for instance, DMF, acetonitrile, chloroform, dichloromethane, or their mixture may be used. Preferably, 4-N,N-dimethylaminopyridine or 4-pyrrolidinopyridine is used as catalyst in the above reaction. 
     When the compounds (I) of the present invention are prepared, if necessary, the functional group of the compound (III) may be protected in usual way. 
     In addition, an acid addition salt of the compounds (I) of the present invention, for example, hydrochloride, oxalate, p-toluenesulfonate, acetate and so on, may be prepared in usual way. 
     Antitumor activities of bis-dioxopiperazine derivatives which the present invention concerns were verified by the growth inhibition or the increase of life span in experimental animals with syngenic tumors such as P388 lymphocytic leukemia, Lewis lung carcinoma, B-16 melanoma and Colon Adenocarcinoma No. 38 as shown below. 
     (1) Animal Test on P388 Lymphocytic Leukemia 
     The treated group to which the compound of the present invention was administered consisted of seven mice, while the control group consisted of ten mice. Six weeks old male mice [CDF 1  (BALB/c×DBA/2), 25±2 g of body weight] were employed as host animals. 
     Tumor cells (1.0×10 6 ) of P388 lymphocytic leukemia were transplanted intraperitoneally into each mouse. The treatment began one day after the transplantation and the prescribed dose of each test compound was administered intraperitoneally to the mice once a day for 9 days or on the 1st and 5th day. 
     Antitumor activity of the test compound was evaluated by the rate of increase in life span (I.L.S.%) which was calculated with the following formula. ##EQU1## T: mean survival time of treated mice C: mean survival time of control mice 
     The results obtained are shown in Table 1A and 1B. 
     
                       TABLE 1A                                                    
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Results of Animal Test on                                                 
P388 Lymphocytic Leukemia                                                 
                     Daily Dose                                           
Test                 × Day                                          
                               I.L.S.                                     
Compound             (mg/kg)   (%)                                        
______________________________________                                    
1,2-bis(4-acetoxymethyl-3,5-                                              
                     200 × 2                                        
                               45                                         
dioxopiperazin-1-yl)ethane                                                
                     60 × 9                                         
                               118                                        
                     20 × 9                                         
                               63                                         
1,2-bis(4-pivaloyloxymethyl-                                              
                     200 × 2                                        
                               66                                         
3,5-dioxopiperazin-1-yl)ethane                                            
                     20 × 9                                         
                               53                                         
1,2-bis(4-chloroacetoxymethyl-                                            
                     200 × 2                                        
                               38                                         
3,5-dioxopiperazin-1-yl)ethane                                            
                     20 × 9                                         
                               54                                         
1,2-bis(4-p-chlorophenoxyacetoxy-                                         
                     200 × 2                                        
                               94                                         
methyl-3,5-dioxopiperazin-1-yl)ethane                                     
                     20 × 9                                         
                               40                                         
1,2-bis[4-(2,4-dichlorophenoxy-                                           
                     200 × 2                                        
                               72                                         
acetoxymethyl)-3,5-dioxopiperazin-                                        
                     60 × 9                                         
                               105                                        
1-yl]ethane          20 × 9                                         
                               49                                         
1,2-bis[4-(2,4,5-trichlorophenoxy-                                        
                     200 × 2                                        
                               94                                         
acetoxymethyl)-3,5-dioxopiperazin-                                        
                     20 × 9                                         
                               65                                         
1-yl]ethane                                                               
1,2-bis[4-(2-p-chlorophenoxy-2-                                           
                     200 × 2                                        
                               114                                        
methylpropionyloxymethyl)-3,5-                                            
                     20 × 9                                         
                               63                                         
dioxopiperazin-1-yl]ethane                                                
1,2-bis(4-p-fluorophenylthio-                                             
                     200 × 2                                        
                               120                                        
acetoxymethyl-3,5-dioxopiperazin-                                         
1-yl)ethane                                                               
1,2-bis(4-p-bromophenylthioacetoxy-                                       
                     200 × 2                                        
                               108                                        
methyl-3,5-dioxopiperazin-1-yl)ethane                                     
1,2-bis(4-phenylacetoxymethyl-                                            
                     200 × 2                                        
                               204                                        
3,5-dioxopiperazin-1-yl)ethane                                            
                     20 × 9                                         
                               143                                        
1,2-bis(4-o-chlorophenylacetoxy-                                          
                     200 × 2                                        
                               83                                         
methyl-3,5-dioxopiperazin-1-yl)ethane                                     
                     20 × 9                                         
                               65                                         
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                       TABLE 1B                                                    
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Results of Animal Test on                                                 
P388 Lymphocytic Leukemia                                                 
                     Daily Dose                                           
Test                 × Day                                          
                               I.L.S.                                     
Compound             (mg/kg)   (%)                                        
______________________________________                                    
1,2-bis(4-p-methoxycinnamoyloxy-                                          
                     200 × 2                                        
                               36                                         
methyl-3,5-dioxopiperazin-1-yl)ethane                                     
                      20 × 9                                        
                               78                                         
1,2-bis[4-(3,4-diacetoxycinnamoyl-                                        
                     200 × 2                                        
                               51                                         
oxymethyl)-3,5-dioxopiperazin-1-yl]-                                      
                      20 × 9                                        
                               35                                         
ethane                                                                    
1,2-bis(4-benzoyloxymethyl-3,5-                                           
                     200 × 2                                        
                               107                                        
dioxopiperazin-1-yl)ethane                                                
                      20 × 9                                        
                               68                                         
1,2-bis(4-o-chlorobenzoyloxymethyl-                                       
                     200 × 2                                        
                               90                                         
3,5-dioxopiperazin-1-yl)ethane                                            
                      20 × 9                                        
                               55                                         
1,2-bis(4-o-fluorobenzoyloxymethyl-                                       
                     200 × 2                                        
                               113                                        
3,5-dioxopiperazin-1-yl)ethane                                            
1,2-bis(4-o-methoxybenzoyloxymethyl-                                      
                     200 × 2                                        
                               99                                         
3,5-dioxopiperazin-1-yl)ethane                                            
                      20 × 9                                        
                               113                                        
1,2-bis[4-(2-furoyloxymethyl)-                                            
                     200 × 2                                        
                               &gt;200                                       
3,5-dioxopiperazin-1-yl]ethane                                            
1,2-bis[4-(2-thenoyloxymethyl)-3,5-                                       
                     200 × 2                                        
                               118                                        
dioxopiperazin-1-yl]ethane                                                
1,2-bis(4-methoxycarbonyloxymethyl-                                       
                     200 × 2                                        
                               103                                        
3,5-dioxopiperazin-1-yl)ethane                                            
                      20 × 9                                        
                               75                                         
1,2-bis(4-ethoxycarbonyloxymethyl-                                        
                     200 × 2                                        
                               45                                         
3,5-dioxopiperazin-1-yl)ethane                                            
                      20 × 9                                        
                               48                                         
1,2-bis(4-isobutoxycarbonyloxymethyl-                                     
                     200 × 2                                        
                               138                                        
3,5-dioxopiperazin-1-yl)ethane                                            
                      60 × 9                                        
                               175                                        
                      20 × 9                                        
                               78                                         
1,2-bis(4-morpholinomethyl-3,5-                                           
                     100 × 2                                        
                               60                                         
dioxopiperazin-1-yl)ethane                                                
                      20 × 9                                        
                               90                                         
(known compound)                                                          
______________________________________                                    
 
    
     Against P388 Lymphocytic leukemia, the compounds of the present invention showed excellent I.L.S.(%). 
     (2) Animal Test on Lewis Lung Carcinoma 
     The treated group to which the compound of the present invention was administered consisted of seven mice, while the control group consisted of ten mice. Six weeks old male mice [BDF 1  (C57BL/6×DBA/2), 25±2 g of body weight] were employed as host animals. 
     Tumor cells (5×10 5 ) of Lewis lung carcinoma were transplanted subcutaneously in inguinal region of each mouse. The treatment began one day after the transplantation and the prescribed dose of each test compound was administered orally to the mice once a day for 8 days. 
     On the 20th day after the transplantation, the tumors of all the mice were excised and weighed. Antitumor activity of the test compound was evaluated by the rate of growth inhibition (G.I.%) which was calculated with the following formula. ##EQU2## T: mean tumor weight of treated mice C: mean tumor weight of control mice 
     The results obtained are shown in Table 2. 
     
                       TABLE 2                                                     
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Results of Animal Test on Lewis Lung Carcinoma                            
                       Daily Dose                                         
                                 G.I.                                     
Test Compound          (mg/kg)   (%)                                      
______________________________________                                    
1,2-bis(4-acetoxymethyl-3,5-dioxo-                                        
                       60        79.6                                     
piperazin-1-yl)ethane                                                     
1,2-bis(4-chloroacetoxymethyl-3,5-                                        
                       50        66.8                                     
dioxopiperazin-1-yl)ethane                                                
1,2-bis(4-o-chlorobenzoyloxymethyl-                                       
                       40        43.7                                     
3,5-dioxopiperazin-1-yl)ethane                                            
1,2-bis(4-methoxycarbonyloxymethyl-                                       
                       60        57.7                                     
3,5-dioxopiperazin-1-yl)ethane                                            
1,2-bis(4-isobutoxycarbonyloxymethyl-                                     
                       50        54.4                                     
3,5-dioxopiperazin-1-yl)ethane                                            
1,2-bis(4-morpholinomethyl-3,5-                                           
                       60        22.6                                     
dioxopiperazin-1-yl)ethane                                                
(known compound)                                                          
______________________________________                                    
 
    
     Against Lewis lung carcinoma, G.I. (%) of the compounds which the present invention concerns were superior to that of a comparative compound, i.e. 1,2-bis(4-morpholinomethyl-3,5-dioxopiperazin-1-yl)ethane. In addition, it was confirmed that the compounds of the present invention suppressed the metastasis of Lewis lung carcinoma significantly as compared with control group. 
     (3) Animal Test on B-16 Melanoma 
     The treated group to which the compound of the present invention was administered consisted of seven mice, while the control group consisted of ten mice. Six weeks old male mice [BDF 1  (C57BL/6×DBA/2) 25±2 g of body weight] were employed as host animals. 
     Tumor cells (5×10 5 ) of B-16 melanoma were transplanted intraperitoneally into each mouse. The treatment began one day after the transplantation and the prescribed dose of each test compound was administered intraperitoneally to the mice once a day for 8 days. 
     Antitumor activity of the test compound was evaluated by the rate of increase in life span (I.L.S.%) which was calculated in the same manner as used in the animal test on P388 lymphocytic leukemia. The results obtained are shown in Table 3. 
     
                       TABLE 3                                                     
______________________________________                                    
Results of Animal Test on B-16 Melanoma                                   
                     Daily Dose                                           
                               I.L.S.                                     
Test Compound        (mg/kg)   (%)                                        
______________________________________                                    
1,2-bis(4-acetoxymethyl-3,5-dioxo-                                        
                     20        39                                         
piperazin-1-yl)ethane                                                     
1,2-bis(4-chloroacetoxymethyl-3,5-                                        
                     20        38                                         
dioxopiperazin-1-yl)ethane                                                
1,2-bis[4-(2,4-dichlorophenoxyacetoxy-                                    
                     20        35                                         
methyl)-3,5-dioxopiperazin-1-yl]ethane                                    
1,2-bis[4-(2-p-chlorophenoxy-2-                                           
                     30        86                                         
methylpropionyloxymethyl)-3,5-                                            
dioxopiperazin-1-yl]ethane                                                
1,2-bis(4-p-fluorophenylthio-                                             
                     40        83                                         
acetoxymethyl-3,5-dioxopiperazin-                                         
1-yl)ethane                                                               
1,2-bis(4-phenylacetoxymethyl-3,5-                                        
                     20        83                                         
dioxopiperazin-1-yl)ethane                                                
1,2-bis(4-benzoyloxymethyl-3,5-                                           
                     20        87                                         
dioxopiperazin-1-yl)ethane                                                
1,2-bis(4-o-chlorobenzoyloxymethyl-                                       
                     20        65                                         
3,5-dioxopiperazin-1-yl)ethane                                            
1,2-bis[4-(2-furoyloxymethyl)-3,5-                                        
                     20        88                                         
dioxopiperazin-1-yl]ethane                                                
1,2-bis(4-methoxycarbonyloxymethyl-                                       
                     30        78                                         
3,5-dioxopiperazin-1-yl)ethane                                            
1,2-bis(4-isobutoxycarbonyloxymethyl-                                     
                     20        86                                         
3,5-dioxopiperazin-1-yl)ethane                                            
1,2-bis(4-morpholinomethyl-3,5-                                           
                     20        40                                         
dioxopiperazin-1-yl)ethane                                                
(known compound)                                                          
______________________________________                                    
 
    
     Against B-16 melanoma, I.L.S.(%) of the compounds which the present invention concerns were nearly equal to or superior to that of the comparative compound. 
     (4) Animal Test on Colon Adenocarcinoma No. 38 
     The treated group to which the compound of the present invention was administered consisted of seven mice, while the control group consisted of ten mice. Six weeks old male mice [BDF 1  (C57BL/6×DBA/2), 25±2 g of body weight] were employed as host animals. 
     Tumor cells (40 mg of fragment) of Colon adenocarcinoma No. 38 were transplanted subcutaneously in inguinal region of each mouse. The treatment began one day after the transplantation and the prescribed dose of each test compound was administered orally to the mice once a day for 8 days. 
     On the 30th day after the transplantation, the tumors of all the mice were excised and weighed. Antitumor activity of the test compound was evaluated by the rate of growth inhibition (G.I.%) which was calculated in the same manner as used in the animal test on Lewis lung carcinoma. The results obtained are shown in Table 4. 
     
                       TABLE 4                                                     
______________________________________                                    
Results of Animal Test on                                                 
Colon Adenocarcinoma No. 38                                               
                       Daily Dose                                         
                                 G.I.                                     
Test Compound          (mg/kg)   (%)                                      
______________________________________                                    
1,2-bis(4-acetoxymethyl-3,5-dioxo-                                        
                       60        68.0                                     
piperazin-1-yl)ethane                                                     
1,2-bis(4-isobutoxycarbonyloxymethyl-                                     
                       60        68.8                                     
3,5-dioxopiperazin-1-yl)ethane                                            
1,2-bis(4-morpholinomethyl-3,5-                                           
                       60        72.8                                     
dioxopiperazin-1-yl)ethane                                                
(known compound)                                                          
______________________________________                                    
 
    
     Against Colon adenocarcinoma No. 38, G.I.(%) of the compound which the present invention concerns were nearly equal to that of the comparative compound. 
     The toxicities of bis-dioxopiperazine derivatives which the present invention concerns were examined by the following tests. 
     (5) Acute Toxicity Test 
     The test group to which the compound of the present invention was administered consisted of ten mice. Five weeks old male mice (ddY, 23±2 g of body weight) were employed as test animals. 
     These animals were intraperitoneally given the test compound which was suspended in the saline solution containing carboxymethyl cellulose (CMC) by 0.5% and were observed for 14 days successively, and LD 50  value of acute toxicity was determined by Litchfield-Wilcoxon method. The results obtained are shown in Table 5. 
     
                       TABLE 5                                                     
______________________________________                                    
Results of the Acute Toxicity Test                                        
                     LD.sub.50 (mg/kg)                                    
Test Compound          i.p.     p.o.                                      
______________________________________                                    
1,2-bis(4-acetoxymethyl-3,5-                                              
                       &gt;1000    &gt;2000                                     
dioxopiperazin-1-yl)ethane                                                
1,2-bis(4-methoxycarbonyloxymethyl-                                       
                       about 500                                          
                                &gt;2000                                     
3,5-dioxopiperazin-1-yl)ethane                                            
1,2-bis(4-isobutoxycarbonyloxymethyl-                                     
                       &gt;850     &gt;1000                                     
3,5-dioxopiperazin-1-yl)ethane                                            
1,2-bis(4-morpholinomethyl-3,5-                                           
                        280     &gt;1000                                     
dioxopiperazin-1-yl)ethane                                                
(known compound)                                                          
______________________________________                                    
 
    
     These data show that the acute toxicity of the compound which the present invention concerns is remarkably lower than that of the comparative compound. 
     The following descriptions are given for the administration routes, pharmaceutical forms and doses when bis-dioxopiperazine derivatives of the present invention are applied to human. 
     The compounds of the present invention may be administered orally in forms such as tablets, powders, granules, capsules, syrups and so on. They may be also administered parenterally in forms such as injections which may include dissolvable freeze-drying form, suppositories and so on. 
     In the preparation of these forms, pharmaceutically acceptable diluent bases, binders, disintegrators, lubricants, suspensions, emulsifiers, antiseptics, stabilizers and dispersing agents, for example, lactose, sucrose, starch, dextrin, crystalline cellulose, kaolin, calcium carbonate, talc, magnesium stearate, distilled water and physiological saline solution may be used. 
     Although the daily doses of these compounds may be varied according to the conditions, ages and weights of the subjects to be treated, the daily doses to adult humans may normally fall within the range of 50 to 3000 mg, preferably 500 to 1000 mg, and may be divided into two or three portions. 
     From the above description, the compounds of the present invention are not only expected useful as antitumor agents and radio-potentiative agents similarly to the known compund of 1,2-bis(4-moropholinomethyl-3,5-dioxopiperazin-1-yl)ethane, but also expected to have a broader antitumor spectrum and more excellent antitumor activity from the results of aforementioned antitumor tests as well as to have lower toxicity than that of the comparative compound. In addition, differently from the comparative compound, the compounds (I) exhibit pharmaceutically advantageous stability to protonic polar solvents. Thus, they have wider pharmaceutical usages as antitumor agents. 
     The preparation methods of the compound (I) claimed in the present invention consist of relatively simple steps in high yields and are suitable for industrial production. 
    
    
     The invention is illustrated by the following examples, but it should be noted that the present invention is not limited to these examples. 
     Preparation 
     1,2-Bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     A mixture of 1,2-bis(3,5-dioxopiperazin-1-yl)ethane (2.0 g, 7.9m mol) and DMF (10 ml) was heated at 130° C. for 10 minutes. To the mixture, 37% aqueous formaldehyde solution (2 ml) was added gradually, and then the mixture was successively heated at 130° C. for 1.5 hours. The reaction mixture was allowed to stand in a refrigerator overnight. The resulting precipitates were collected, washed with ethyl acetate and dried under reduced pressure to give the tilted compound (1.6 g; yield 64.7%). 
     Melting Point: 170° to 172° C. (recrystallized from dioxane). 
     Elementary Analysis (%): Calculated for C 12  H 18  N 4  O 6  : C 45.86; H 5.77; N 17.83. Found: C 45.83; H 5.73; N 17.73. 
     EXAMPLE 1 
     1,2-Bis(4-acetoxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     A mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (1.50 g, 4.8 m mol), pyridine (10 ml) and acetic anhydride (5 ml, 52.9 m mol) was stirred for 12 hours at room temperature. The reaction mixture was diluted with ethyl acetate (20 ml) and the resulting crystals were collected and washed with ethyl acetate and successively with ether and was dried under reduced pressure to give the titled compound (1.34 g; yield 70.5%). 
     Melting Point: 178° to 181° C. (recrystallized from dioxane). 
     Elementary Analysis (%): Calculated for C 16  H 22  N 4  O 8  : C 48.24; H 5.57; N 14.06. Found: C 48.02; H 5.48; N 13.88. 
     Infrared Absorption (IR) Spectrum (KBr) cm -1  : 1740, 1700 (C═O). 
     Nuclear Magnetic Resonance (NMR) Spectrum (DMSO-d 6 ) δppm: 2.01 (6H, s, --COCH 3  ×2) 2.64 (4H, s, &gt;NCH 2  CH 2  N&lt;) 3.58 (8H, s, &gt;NCH 2  CO--×4), 5.60 (4H, s, &gt;NCH 2  O--×2). 
     EXAMPLE 2 
     1,2-Bis(4-pivaloyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (0.94 g, 3.0 m mol) and pyridine (25 ml), pivaloyl chloride (0.78 g, 6.5 m mol) dissolved in pyridine (5 ml) was added gradually at 0° C., and then the mixture was stirred for 18 hours at room temperature. The solvent was removed from the reaction mixture under reduced pressure, and the residue was extracted with ethyl acetate (200 ml). The extract solution was washed with a saturated sodium bicarbonate aqueous solution and successively with water and was dried over magnesium sulfate. The residue obtained by removing the solvent from the extract under reduced pressure was purified by silica gel column chromatography (ethyl acetate, Rf value=0.8) to give the titled compound (0.75 g; yield 52%). 
     Melting Point: 114° to 118° C. 
     IR Spectrum (KBr) cm -1  : 1720, 1700 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 1.18 (18H, s, --C(CH 3 ) 3  ×2), 2.69 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.54 (8H, s, &gt;NCH 2  CO--×4), 5.76 (4H, s, &gt;NCH 2  O--×2). 
     In accordance with the procedure of Example 2, the following compounds were obtained from the corresponding starting materials. 
     1,2-Bis(4-isovaleryloxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 62%) 
     Melting Point: 72° to 75.5° C. 
     IR Spectrum (KBr)cm -1  : 1730, 1695 (C═O). ##STR4## 1,2-Bis(4-palmitoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 30%) 
     Melting Point: 92° to 94° C. 
     IR Spectrum (KBr) cm -1  : 1740, 1685 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 0.88 (6H, t, J=7 Hz, --CH 3  ×2), 1.1 to 1.4 (52H, m, --(CH 2 ) 13  --×2), 2.30 (4H, t, J=7 Hz, --COCH 2  --×2), 2.68 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.53 (8H, s, &gt;NCH 2  CO--×4), 5.77 (4H, s, &gt;NCH 2  O--×2). 
     1,2-Bis[4-(2-p-chlorophenoxy-2-methylpropionylmethyl)-3,5-dioxopiperazin-1-yl]ethane (yield 82%) 
     Melting Point: 108° C. (recrystallized from chloroform). 
     EXAMPLE 3 
     1,2-Bis(4-cyclohexylcarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (0.32 g, 1.0 m mol) and pyridine (9 ml), cyclohexanecarbonyl chloride (0.3 ml, 2.2 m mol) was added gradually, and then the mixture was stirred for 12 hours at room temperature. The reaction mixture was diluted with ethyl acetate (100 ml) and was washed with 10% sulfuric acid solution and successively with water and was dried. The crude product obtained by removing the solvent under reduced pressure from the above mixture was purified by silica gel column chromatography (ethyl acetate: chloroform=2:1, Rf value=0.6) to give the oily titled compound (0.16 g, yield 30%). 
     IR Spectrum (KBr) cm -1  : 1730, 1695 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 1.2 to 2.3 (22H, m, cyclohexyl H), 2.69 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.53 (8H, s, &gt;NCH 2  CO--×4), 5.76 (4H, s, &gt;NCH 2  O--×2). 
     In accordance with the procedure of Example 3, the following compound was obtained from the corresponding starting material. 
     1,2-Bis(4-phenylacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     Melting Point: 130° to 132° C. (recrystallized from ethylene glycol monomethylether). 
     EXAMPLE 4 
     1,2-Bis(4-chloroacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     A mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (3.1 g, 9.9 m mol), pyridine (1.6 ml) and chloroform (50 ml) was stirred at 10° C. To the mixture, chloroacetyl chloride (1.8 ml, 22.6 m mol) was added gradually, and then the mixture was stirred for 6  hours at room temperature. The reaction mixture was diluted with chloroform (50 ml), was washed with water and was dried successively. The residue obtained by removing the solvent under reduced pressure from the above mixture was recrystallized by ethylene glycol monomethylether to give the titled compound (2.6 g; yield 60.5%) 
     Melting Point: 132.5° to 133.5° C. 
     Elementary Analysis (%): Calculated for C 16  H 20  N 4  O 8  Cl 2 .1/2H 2  O: C 40.37; H 4.45; N 11.77. Found: C 40.17; H 4.14; N 11.44. 
     IR Spectrum (KBr) cm -1  : 1760, 1680 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 2.68 (4H, s, &gt;NCH 2  CH 2  N&lt;) 3.50 (8H, s, &gt;NCH 2  CO--×4), 4.20 (4H, s, --CH 2  Cl×2), 5.82 (4H, s, &gt;NCH 2  O--×2). 
     In accordance with the procedure of Example 4, the following compound was obtained from the corresponding starting material. 
     1,2-Bis(4-isobutoxycarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 88%). 
     Melting Point: 128° to 130° C. (recrystallized from ethylene glycol monomethylether). 
     Elementary Analysis (%): Calculated for C 22  H 34  N 4  O 10  : C 51.36; H 6.61; N 10.89. Found: C 51.12; H 6.70; N 10.86. 
     IR Spectrum (KBr) cm -1  : 1750, 1700 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 0.94 (12H, d, J=7 Hz, --CH 2  CH(CH 3 ) 2  ×2), 1.92 to 2.02 (2H, m, --CH 2  CH(CH 3 ) 2  ×2), 2.68 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.52 (8H, s, &gt;NCH 2  CO--×4), 3.94 (4H, d, J=7 Hz, --CH 2  CH(CH 3 ) 2  ×2), 5.82 (4H, s, &gt;NCH 2  O--×2). 
     EXAMPLE 5 
     1,2-Bis(4-β-carboxypropionyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (1.0 g, 3.2 m mol) and DMF (20 ml), succinic anhydride (0.7 g, 7.0 m mol) and triethylamine (0.7 g) were added, and then the mixture was stirred for 24 hours at room temperature. Further, the reaction mixture was stirred for 12 hours after addition of chloromethyl benzyl ether (1.2 g), then the solvent was removed under reduced pressure. The residue was extracted with chloroform, and the extract solution was washed with water and dried. The residue obtained by removing the solvent was purified by silica gel column chromatography (chloroform:methanol=20:1, Rf value=0.6) to give benzyloxymethyl ester of the titled compound (0.9 g). 
     The ester was dissolved in a mixture (30 ml) of ethyl acetate and ethanol (3:1). After addition of 10% palladium carbon (0.2 g), the mixture was stirred for 24 hours at room temperature under hydrogen. Then, after filtering off the catalyst, the solvent was removed from the filtrate to give the viscous and oily titled compound (0.6 g; yield 37%). 
     IR Spectrum (neat) cm -1  : 1760, 1740, 1700 (C═O). 
     NMR Spectrum (DMSO-d 6 ) δppm: 2.4 to 2.6 (8H, m, --COCH 2  CH 2  CO--×2), 2.65 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.59 (8H, s, &gt;NCH 2  CO--×4), 5.62 (4H, s, &gt;NCH 2  O--×2). 
     The titled compound thus obtained (0.93 g) was suspended in water (10 ml). To the suspension, 1.73% aqueous sodium carbonate solution (10 ml) was gradually added, and the mixture was stirred for ten minutes at room temperature. The reaction mixture was filtered and the filtrate was freeze-dried to give the colorless powdery sodium salt of the titled compound (0.91 g). 
     IR Spectrum (KBr) cm -1  : 1740, 1700, 1590 (C═O). ##STR5## 
     EXAMPLE 6 
     1.2-Bis[4-(2,4-dichlorophenoxyacetoxymethyl)-3,5-dioxopiperazin-1-yl]ethane 
     A mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (1.0 g, 3.2 m mol), DMF (10 ml) and pyridine (1 ml) was stirred at room temperature, and 2,4-dichlorophenoxyacetyl chloride (1.6 g, 6.7 m mol) was added gradually at room temperature. The mixture was stirred for 4 hours and then was allowed to stand overnight at room temperature. The reaction mixture was poured into ice water. The resulting precipitates were collected, washed with cooled water and dried, and were recrystallized by ethylene glycol monomethyl ether to give the titled compound (1.0 g; yield 43.6%). 
     Melting Point: 153° to 155° C. 
     Elementary Analysis (%): Calculated for C 28  H 26  N 4  O 20  Cl 4  : C 46.96; H 3.64; N 7.78. Found: C 46.41; H 3.94; N 7.5. 
     IR Spectrum (KBr) cm -1  : 1760, 1690 (C═O). ##STR6## 
     In accordance with the procedure of Example 6, the following compounds were obtained from the corresponding starting materials. 
     1,2-Bis(4-p-chlorophenoxyacetoxymethyl-3,5-dioxo-piperazin-1-yl)ethane (yield 50%) 
     Melting Point: 155° to 156° C. (recrystallized from ethylene glycol monomethylether). 
     Elementary Analysis (%): Calculated for C 28  H 28  N 4  O 10  Cl 2  : C 51.61; H 4.30; N 8.60. Found: C 51.45; H 4.46; N 8.78. 
     1,2-Bis[4-(2,4,5-trichlorophenoxyacetoxymethyl)-3,5-dioxopiperazin-1-yl]ethane (yield 85%) 
     Melting Point: 140° to 141° C. (recrystallized from ethylene glycol monomethylether). 
     1,2-Bis(4-p-bromophenylthioacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 67%) 
     Melting Point: 138° to 139° C. (recrystallized from ethylene glycol monomethylether). 
     1,2-Bis(4-p-fluorophenylthioacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 55%) 
     Melting Point: 103° to 104° C. (recrystallized from ethylene glycol monomethylether). 
     EXAMPLE 7 
     1,2-Bis(4-o-chlorophenylacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     To a mixture of 1-methyl-2-chloropyridinium iodide (1.02 g), acetonitrile (10 ml), triethylamine (1.1 ml) and 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (0.64 g, 2.0 m mol), o-chlorophenylacetic acid (0.68 g, 4.0 m mol) dissolved in acetonitrile (10 ml) was added, and then the mixture was stirred for 12 hours at room temperature. The residue obtained by removing the solvent was purified by silical gel column chromatography (chloroform:methanol=20:1, Rf value=0.6) to give the titled compound (0.41 g; yield 33%). 
     Melting Point: 157° to 162° C. 
     IR Spectrum (KBr) cm -1  : 1740, 1690 (C═O). ##STR7## 
     In accordance with the procedure of Example 7, the following compound was obtained from the corresponding starting material. Instead of acetonitrile, DMF was used as the reaction solvent. 
     1,2-Bis(4-o-bromophenylacetoxymethyl-3,5-dixopiperazin-1-yl)ethane (yield 25%) 
     Melting Point: 164° to 168° C. 
     IR Spectrum (KBr) cm -1  : 1740, 1700 (C═O). ##STR8## 
     EXAMPLE 8 
     1,2-Bis(4-α-hydroxy-α-phenylacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (2.4 g, 7.6 m mol) and pyridine (20 ml), α-chloroacetoxy-α-phenylacetyl chloride (3.1 g, 16.7 m mol) was added at 0° C., and then the mixture was stirred for 1 hour at 0° C. and successively for 4 hours at room temperature. The reaction mixture was added to water and was extracted with chloroform. The extract solution was washed with 10% sulfuric acid solution and successively with water, and was dried over magnesium sulfate. The oily product obtained by removing the solvent under reduced pressure was purified by silica gel column chromatography (ethyl acetate, Rf value=0.5) to give the oily titled compound having chloroacetoxy radical (1.0 g). A mixture of the compound, thiourea (0.4 g, 5.2 m mol), sodium acetate (0.89 g, 10 m mol) and THF (20 ml) was stirred for 4 hours at room temperature. Then, the solvent was removed under reduced pressure and the residue was extracted with chloroform. The residue obtained by concentrating the extract solution was purified by column chromatography (ethyl acetate:acetone=9:1, Rf value=0.6) to give the oily titled compound (0.2 g). 
     IR Spectrum (neat) cm -1  : 1735, 1700 (C═O). ##STR9## 
     EXAMPLE 9 
     1,2-Bis[4-(3,4-methylenedioxybenzoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (0.94 g, 3.0 m mol) and pyridine (10 ml), piperonyloyl chloride (1.00 g, 6.0 m mol) dissolved in pyridine (10 ml) was added, and then the mixture was stirred for 20 hours at room temperature. To the reaction mixture, chloroform (250 ml) was added and the solution was washed with 10% sulfuric acid solution and successively with water, further was washed with aqueous sodium bicarbonate solution and successively with water. Then, the solvent was removed under reduced pressure to give the titled compound (1.12 g; yield 61%). 
     Melting Point: 195° to 198° C. 
     IR Spectrum (KBr) cm -1  : 1720, 1695 (C═O). ##STR10## 
     In accordance with the procedure of Example 9, the following compounds were obtained from the corresponding starting materials. 
     1,2-Bis(4-cinnamoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 47%) 
     Melting Point: 149° to 152° C. 
     IR Spectrum (KBr) cm -1  : 1710, 1695 (C═O). ##STR11## 1,2-Bis-[4-(3,4-diacetoxycinnamoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane (yield 35%) 
     Melting Point: 83° to 87° C. 
     IR Spectrum (KBr) cm -1  : 1750, 1695 (C═O). ##STR12## 1,2-Bis-(4-p-methoxycinnamoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 75%) 
     Melting Point: 100° to 103° C. 
     IR Spectrum (KBr) cm -1  : 1700, 1600 (C═O). ##STR13## 1,2-Bis[4-(3,4-dimethoxycinnamoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane (yield 54%) 
     Melting Point: 195° to 198° C. 
     IR Spectrum (KBr) cm -1  : 1720, 1695 (C═O). ##STR14## 
     EXAMPLE 10 
     1,2-Bis(4-o-chlorobenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (1.26 g, 4.0 m mol) and pyridine (12 ml), o-chlorobenzoyl chloride (1.40 g, 8.0 m mol) was added at 0° C., and then the mixture was stirred for 1 hour at 0° C., then successively for 12 hours at room temperature. The reaction mixture was added to water and was extracted with chloroform. The extract solution was washed with 10% sulfuric acid solution and successively with water, and then was dried over magnesium sulfate. The light yellow compound obtained by concentrating the extract solution under reduced pressure was purified by silica gel column chromatography (ethyl acetate:acetone=9:1, Rf value=0.5) to give the titled compound (1.19 g; yield 50.1%). 
     Melting Point: 161° to 165° C. 
     Elementary Analysis (%): Calculated for C 26  H 24  N 4  O 8  Cl 2  : C 52.80; H 4.09; N 9.47. Found: C 52.55; H 4.18; N 9.22. 
     IR Spectrum (KBr) cm -1  : 1730, 1695 (C═O). ##STR15## 
     In accordance with the procedure of Example 10, the following compounds were obtained from the corresponding starting materials. 
     1,2-Bis(4-benzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 54.2%) 
     Melting Point: 164° to 166° C. 
     IR Spectrum (KBr) cm -1  : 1730, 1710 (C═O). ##STR16## 1,2-Bis(4-o-fluorobenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 75%) 
     Melting Point: 151° to 152° C. 
     1,2-Bis(4-o-methoxybenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 92%) 
     Melting Point: 163° to 164° C. (recrystallized from ethylene glycol monomethylether). 
     1,2-Bis(4-methoxyacetoxymethyl-3,5-dioxopiperazin-1yl)ethane (yield 74%) 
     Melting Point: 117° to 120° C. 
     IR Spectrum (KBr) cm -1  : 1740, 1700 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 2.71 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.42 (8H, s, &gt;NCH 2  CO--×4), 3.55 (6H, s, --OCH 3  ×2), 4.03 (4H, s, --COCH 2  O--×2), 5.83 (4H, s, &gt;NCH 2  O--×2). 
     EXAMPLE 11 
     1,2-Bis[4-(3-pyridylcarbonyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane 
     A mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (0.31 g, 1.0 m mol), 3-pyridylcarbonyl chloride (0.28 g, 2.0 m mol) and pyridine (10 ml) was stirred for 18 hours at room temperature. The solvent was removed from the reaction mixture under reduced pressure and the residue was extracted with chloroform. The extract solution was washed with saturated sodium bicarbonate aqueous solution successively with water, and was dried over magnesium sulfate. The residue obtained by removing the solvent under reduced pressure from the extract solution was purified by silica gel column chromatography (chloroform:ether:methanol=6:1:1, Rf value=0.3) to give the titled compound (0.12 g; yield 24%). 
     Melting Point: 182° to 188° C. 
     IR Spectrum (KBr) cm -1  : 1710, 1690 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 2.74 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.59 (8H, s, &gt;NCH 2  CO--×4), 6.06 (4H, s, &gt;NCH 2  O--×2), 7.4 to 9.2 (8H, m, pyridyl H). 
     In accordance with the procedure of Example 11, the following compounds were obtained from the corresponding starting materials. 
     1,2-Bis[4-(2-pyridylcarbonyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane 
     Melting Point: 163° to 168° C. 
     IR Spectrum (KBr) cm -1  : 1740, 1700 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 2.72 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.58 (8H, s, &gt;NCH 2  CO--×4), 6.09 (4H, s, &gt;NCH 2  O--×2), 7.5 to 8.7 (8H, m, pyridyl H). 
     1,2-Bis[4-(4-pyridylcarbonyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane 
     Melting Point: 210° to 220° C. 
     IR Spectrum (KBr) cm -1  : 1730, 1700 (C═O). 
     NMR Spectrum (DMSO-d 6 ) δppm: 2.70 (4H, s, &gt;NCH 2  CH 2  N&lt;) 3.65 (8H, s, &gt;NCH 2  CO--×4) 5.92 (4H, s, &gt;NCH 2  O--×2), 7.77 (4H, d, J=5 Hz, pyridyl H), 8.79 (4H, d, J=5 Hz, pyridyl H). 
     EXAMPLE 12 
     1,2-Bis[4-(2-thenoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (6.30 g, 22 m mol) and pyridine (60 ml), thenoyl chloride (6.45 g, 44 m mol) was added gradually at 0° C., and then the mixture was stirred for 4 hours at room temperature. The solvent was removed from the reaction mixture under reduced pressure, and the residue was extracted with chloroform. The extract solution was washed with 10% sulfuric acid solution and successively with water, and was dried over magnesium sulfate. The residue obtained by removing the solvent from the extract solution under reduced pressure was purified by silica gel column chromatography (ethyl acetate, Rf value=0.6) to give the titled compound (8.20 g; yield 70%). 
     Melting Point: 158° to 160° C. (recrystallized from ethylene glycol monomethylether). ##STR17## 
     In accordance with the procedure of Example 12, the following compound was obtained from the corresponding starting material. 
     1,2-Bis[4-(2-furoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane (yield 52%). 
     Melting Point: 166° to 167° C. (recrystallized from ethylene glycol monomethylether). 
     EXAMPLE 13 
     1,2-Bis(4-methoxycarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (2.20 g, 7.0 m mol) and pyridine (20 ml), methyl chloroformate (1.41 g, 14.9 m mol) was added gradually at 0° C., and the mixture was stirred for 1.5 hours at 0° C., then successively for 3 hours at room temperature. The reaction mixture was added to water and was extracted with chloroform. The extract solution was washed with 10% sulfuric acid solution and successively with water, and was dried over magnesium sulfate. The crystals obtained by concentrating the extract solution under reduced pressure were washed with ethyl acetate and dried under reduced pressure to give the titled compound (1.76 g; yield 58.6%). 
     Melting Point: 162.5° to 164.5° C. 
     Elementary Analysis (%): Calculated for C 16  H 22  N 4  O 10  : C 44.65; H 5.15; N 13.02. Found: C 44.55; H 5.21; N 12.96. 
     IR Spectrum (KBr) cm -1  : 1760, 1705 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 2.67 (4H, s, &gt;NCH 2  CH 2  N&gt;), 3.52 (8H, s, &gt;NCH 2  CO--×4), 3.80 (6H, s, --OCH 3  ×2), 5.81 (4H, s, &gt;NCH 2  O--×2). 
     In accordance with the procedure of Example 13, the following compound was obtained from the corresponding starting material. 
     1,2-Bis(4-ethoxycarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 86%) 
     Melting Point: 99.5° to 102.5° C. 
     IR Spectrum (KBr) cm -1  : 1735, 1695 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 1.30 (6H, t, J=7 Hz, --OCH 2  CH 3  ×2), 2.67 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.52 (8H, s, &gt;NCH 2  CO--×4), 4.22 (4H, q, J=7 Hz, --OCH 2  CH 3  ×2), 5.81 (4H, s, &gt;NCH 2  O--×2). 
     EXAMPLE 14 
     1,2-Bis(4-n-butoxycarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (1.26 g, 4.0 m mol) and pyridine (10ml), n-butyl chloroformate (1.37 g, 10 m mol) was added gradually at 0° C., and then the mixture was stirred for 12 hours at room temperature. The reaction mixture was added to water (100 ml) and was extracted with chloroform. The extract solution was washed with water and successively with 5% sulfuric acid solution and with water, and then was dried over magnesium sulfate. The residue obtained by concentrating the extract solution under reduced pressure was purified by silica gel column chromatography (ethyl acetate, Rf value=0.65) to give the titled compound (1.43 g; yield 69%). 
     Melting Point: 68° to 71° C. 
     IR Spectrum (KBr) cm -1  : 1740, 1695 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 0.92 (6H, t, --OCH 2  CH 2  CH 2  CH 3  ×2), 1.34 to 1.43 (4H, m, --OCH 2  CH 2  CH 2  CH 3  ×2), 1.59 to 1.67 (4H, m, --OCH 2  CH 2  CH 2  CH 3  ×2), 2.67 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.52 (8H, s, &gt;NCH 2  CO--×4), 4.13 to 4.18 (4H, m, --OCH 2  CH 2  CH 2  CH 3  ×2), 5.81 (4H, s, &gt;NCH 2  O--×2). 
     In accordance with the procedure of Example 14, the following compounds were obtained from the corresponding starting materials. 
     1,2-Bis[4-(2-ethylhexyloxycarbonyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane (yield 86%) 
     Melting Point: 58° to 61° C. 
     IR Spectrum (KBr) cm -1  : 1740, 1700 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 0.85 to 0.91 (12H, m, --CH 2  CH 3  ×2.--(CH 2 ) 3  CH 3  ×2) 1.27 to 1.38 (16H, m, --CH 2  CH 3  ×2.--(CH 2 ) 3  CH 3  ×2), 1.56 to 1.64 (2H, m, --OCH 2  CH&lt;×2), 2.67 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.52 (8H, s, &gt;NCH 2  CO--×4), 4.06 to 4.09 (4H, m, --OCH 2  CH&lt;×2), 5.81 (4H, s, &gt;NCH 2  O--×2). 
     1,2-Bis(4-phenoxycarbonyloxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 60%) 
     Melting Point: 138° to 140° C. 
     IR Spectrum (KBr) cm -1  : 1750, 1700 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 2.69 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.56 (8H, s, &gt;NCH 2  CO--×4), 5.92 (4H, s, &gt;NCH 2  O--×2), 7.16 to 7.41 (10H, m, aromatic H). 
     1,2-Bis(4-p-nitrobenzyloxycarbonyloxymethyl-3,5- dioxopiperazin-1-yl)ethane (yield 49%) 
     Melting Point: 158° to 160.5° C. 
     IR Spectrum (KBr) cm -1  : 1750, 1700 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 2.68 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.53 (8H, s, &gt;NCH 2  CO--×4), 5.27 (4H, s, --OCH 2  --Ph×2), 5.85 (4H, s, &gt;NCH 2  O--×2), 7.53 (4H, s, J=8.6 Hz, aromatic H), 8.23 (4H, d, J=8.6 Hz, aromatic H). 
     EXAMPLE 15 
     1,2-Bis(4-o-methoxybenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (3.14 g, 10 m mol), o-methoxybenzoic acid (3.35 g, 22 m mol), 4-N,N-dimethylaminopyridine (0.20 g) and dichloromethane (60 ml), dicyclohexylcarbodiimide (4.12 g, 20 m mol) was added gradually at 0° C., and then the mixture was stirred for 6 hours at room temperature. The reaction mixture was filtered and the filtrate was washed with water and dried. The residue obtained by removing the solvent from the filtrate under reduced pressure was recrystallized from ethylene glycol monomethylether to give the titled compound (1.81 g; yield 31%). 
     Melting Point: 163° to 164° C. 
     Elementary Analysis (%): Calculated for C 28  H 30  N 4  O 10  : C 57.73; H 5.19; N 9.62. Found: C 57.77; H 5.30; N 9.48. 
     NMR Spectrum (CDCl 3 ) δppm: 2.70 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.55 (8H, s, &gt;NCH 2  CO--×4), 3.88 (6H, s, --OCH 3  ×2), 5.99 (4H, s, &gt;NCH 2  O--×2), 6.91 to 6.97 (4H, m, aromatic H), 7.43 to 7.50 (2H, m, aromatic H), 7.72 to 7.75 (2H, m, aromatic H). 
     In accordance with the procedure 15, the following compounds were obtained from the corresponding starting materials. 
     1,2-Bis[4-(2-thenoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane (yield 43%) 
     Melting Point: 158° to 160° C. 
     Elementary Analysis (%): Calculated for C 22  H 22  N 4  S 2  O 8  : C 49.42; H 4.15; N 10.48. Found: C 49.66; H 4.29; N 10.61. ##STR18## 1,2-Bis[4-(2-furoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane (yield 42%) 
     Melting Point: 166° to 167° C. 
     Elementary Analysis (%): Calculated for C 22  H 22  N 4  O 10 .1/2H 2  O: C 51.66; H 4.53; N 10.96. Found: C 51.79; H 4.41; N 10.89. ##STR19## 1,2-Bis[4-(2-naphthyloxyacetoxymethyl)-3,5-dioxopiperazin-1-yl]ethane (yield 30%) 
     Melting Point: 193° to 195° C. 
     Elementary Analysis (%): Calculated for C 36  H 34  N 4  O 10 .1/2H 2  O: C 62.51; H 5.10; N 8.10. Found: C 62.65; H 5.11; N 7.90. 
     NMR Spectrum (DMSO-d 6 ) δppm: 2.60 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.58 (8H, s, &gt;NCH 2  CO--×4), 4.92 (4H, s, --COCH 2  O--×2), 5.79 (4H, s, &gt;NCH 2  O--×2), 7.20 to 7.88 (14H, m, naphthyl H). 
     1,2-Bis[4-(2-p-chlorophenoxy-2-methylpropionyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane (yield 30%) 
     Melting Point: 108° C. (recrystallized from chloroform). 
     Elementary Analysis (%): Calculated for C 32  H 36  N 4  O 10  Cl 2  : C 54.32; H 5.13; N 7.92. Found: C 54.07; H 5.01; N 7.76. ##STR20## 1,2-Bis(4-p-bromophenythioacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 44%) 
     Melting Point: 138° to 139° C. 
     Elementary Analysis (%): Calculated for C 28  H 28  N 4  S 2  O 8  Br 2  : C 43.53; H 3.65; N 7.25. Found: C 43.66; H 3.82; N 7.21. 
     NMR Spectrum (CDCl 3 ) δppm: 2.65 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.49 (8H, s, &gt;NCH 2  CO--×4), 3.59 (4H, s, --COCH 2  S--×2), 5.79 (4H, s, &gt;NCH 2  O--×2), 7.27 (4H, d, J=8 Hz, aromatic H), 7.42 (4H, d, J=8 Hz, aromatic H). 
     1,2-Bis(4-p-fluorophenylthioacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane (yield 48%) 
     Melting Point: 103° to 104° C. 
     IR Spectrum (KBr) cm -1  : 1740, 1690 (C═O). 
     NMR Spectrum (CDCl 3 ) δppm: 2.66 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.50 (8H, s, &gt;NCH 2  CO--×4), 3.53 (4H, s, --COCH 2  S--×2), 5.78 (4H, s, &gt;NCH 2  O--×2), 6.97 to 7.04 (4H, m, aromatic H), 7.40 to 7.47 (4H, m, aromatic H). 
     1,2-Bis[4-(1-naphthylacetoxymethyl)-3,5-dioxopiperazin-1-yl]ethane (yield 45%) 
     Melting Point: 223° to 224° C. (recrystallized from chloroform). 
     Elementary Analysis (%): Calculated for C 36  H 34  N 4  O 8 .1/2H 2  O: C 65.54; H 5.35; N 8.49. Found: C 65.60; H 5.15; N 8.39. ##STR21## 
     EXAMPLE 16 
     1,2-Bis(4-β-methoxycarbonylpropionyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (1.57 g, 5 m mol), methyl hydrogen succinate (1.32 g, 10 m mol), 4-N,N-dimethylaminopyridine (0.10 g) and dry dichloromethane (30 ml), dicyclohexylcarbodiimide (2.06 g, 10 m mol) dissolved in dry dichloromethane (10 ml) was added gradually at 0° C., and then the reaction mixture was stirred for 1 day at room temperature and filtered. The filtrate was washed with 5% aqueous acetic acid solution and successively with water and was dried. The solvent was removed from the filtrate under reduced pressure to give the titled compound (2.24 g; yield 83%). 
     Melting Point: 134° to 139° C. (recrystallized from ethylene glycol monomethylether). 
     IR Spectrum (KBr) cm -1  : 1720, 1700 (C═O). 
     NMR Spectrum (DMSO-d 6 ) δppm: 2.5 to 2.6 (8H, m, --COCH 2  CH 2  CO--×2), 2.65 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.30 (6H, s, --COOCH 3  ×2), 3.58 (8H, s, &gt;NCH 2  CO--×4), 5.76(4H, s, &gt;NCH 2  O--×2). 
     In accordance with the procedure of Example 16, the following compounds were obtained from the corresponding starting materials. 
     1,2-Bis(4-m-toluoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     Melting Point: 157° to 158° C. (recrystallized from ethylene glycol monomethylether). 
     Elementary Analysis (%): Calculated for C 28  H 30  N 4  O 8 .1/2H 2  O: C 60.10; H 5.58; N 10.01. Found: C 60.34; H 5.44; N 10.03. 
     1,2-Bis(4-o-toluoyloxymethyl)-3,5-dioxopiperazin-1-yl)ethane 
     Melting Point: 155° to 156° C. (recrystallized from ethyl acetate). 
     Elementary Analysis (%): Calculated for C 28  H 30  N 4  O 8  : C 61.08; H 5.49; N 10.18. Found: C 61.17; H 5.69; N 10.22. 
     NMR Spectrum (CDCl 3 ) δppm: 2.57 (6H, s, --CH 3  ×2), 2.70 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.56 (8H, s, &gt;NCH 2  CO--×4), 6.00 (4H, s, &gt;NCH 2  O--×2), 7.18 to 7.85 (8H, m, aromatic H). 
     1,2-bis(4-o-fluorobenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     Melting Point: 151° to 152° C. 
     NMR Spectrum (CDCl 3 ) δppm: 2.73 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.59 (8H, s, &gt;NCH 2  CO--×4), 6.04 (4H, s, &gt;NCH 2  O--×2), 7.07 to 7.92 (8H, m, aromatic H). 
     1,2-Bis[4-(1-naphthoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane 
     Melting Point: 206° to 207° C. (recrystallized from ethylene glycol monomethylether). 
     Elementary Analysis (%): Calculated for C 34  H 30  N 4  O 8 .1/2H 2  O: C 64.65; H 4.95; N 8.87. Found: C 64.36; H 4.89; N 8.77. 
     NMR Spectrum (CDCl 3 ) δppm: 2.70 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.57 (8H, s, &gt;NCH 2  CO--×4), 6.11 (4H, s, &gt;NCH 2  O--×2), 7.43 to 8.89 (14H, m, aromatic H). 
     1,2-Bis(4-phenylacetoxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     Melting Point: 130° to 132° C. (recrystallized from ethylene glycol monomethylether). 
     Elementary Analysis (%): Calculated for C 28  H 30  N 4  O 8  : C 61.08; H 5.49; N 10.18. Found: C 61.15; H 5.69; N 10.49. 
     NMR Spectrum (CDCl 3 ) δppm: 2.62 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.51 (8H, s, &gt;NCH 2  CO--×4), 3.63 (4H, s, --COCH 2  --Ph×2), 5.81 (4H, s, &gt;NCH 2  O--×2), 7.23 to 7.34 (10H, m, aromatic H). 
     1,2-Bis[4-2,4,5-trichlorophenoxyacetoxymethyl)-3,5-dioxopiperazin-1-yl]ethane 
     Melting Point: 140° to 141° C. (recrystallized from ethylene glycol monomethylether). 
     Elementary Analysis (%): Calculated for C 28  H 24  N 4  O 10  Cl 6  : C 42.62; H 3.07; N 7.10. Found: C 42.77; H 3.18; N 6.90. 
     NMR Spectrum (CDCl 3 ) δppm: 2.68 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.53 (8H, s, &gt;NCH 2  CO--×4), 4.71 (4H, s, --COCH 2  O--×2), 5.90 (4H, s, &gt;NCH 2  O--×2), 6.95 (2H, s, aromatic H), 7.47 (2H, s, aromatic H). 
     EXAMPLE 17 
     1,2-Bis(4-o-carboxybenzoyloxymethyl-3,5-dioxopiperazin-1-yl)ethane 
     To a mixture of benzyl hydrogen phthalate (1.69 g, 6.6 m mol), 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (0.94 g, 3 m mol), 4-N,N-dimethylaminopyridine (0.05 g) and dry dichloromethane (30 ml), dicyclohexylcarbodiimide (1.24 g, 6 m mol) dissolved in dry dichloromethane (10 ml) was added gradually at 0° C., and then the reaction mixture was stirred overnight at room temperature and filtered. The filtrate was washed with 5% aqueous acetic acid solution and successively with saturated sodium bicarbonate aqueous solution and was dried. The residue obtained by removing the solvent from the filtrate under reduced pressure was purified by silica gel column chromatography (ethyl acetate:chloroform=7:3) to give benzyl ester of the titled compound (1.16 g; yield 49%; melting point 50° to 52° C.). To a solution of this ester (1.16 g, 1.47 m mol) in ethyl acetate (20 ml), 10% palladium-carbon (0.10 g) was added and the mixture was stirred overnight under hydrogen at room temperature. The reaction mixture was filtered and the solvent was removed from the filtrate under reduced pressure to give the titled compound (0.40 g; yield 45%). 
     Melting Point: 167° to 169° C. 
     IR Spectrum (KBr) cm -1  : 1700 (C═O). 
     NMR Spectrum (DMSO-d 6 ) δppm: 2.67 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.61 (8H, s, &gt;NCH 2  CO--×4), 5.84 (4H, s, &gt;NCH 2  O--×2), 7.5 to 7.8 (8H, m, aromatic H), 13.27 (2H, broad s, --COOH). 
     EXAMPLE 18 
     1,2-Bis[4-(p-aminobenzoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane 
     To a mixture of 1,2-bis(4-hydroxymethyl-3,5-dioxopiperazin-1-yl)ethane (0.63 g, 2.0 m mol) and pyridine (10 ml), p-benzyloxycarbonylaminobenzoyl chloride (1.27 g, 4.4 m mol) dissolved in pyridine (12 ml) was added gradually at 0° C. and then the reaction mixture was stirred for 1 hour at 0° C. and successively for 16 hours at room temperature. The residue obtained by removing the solvent from the reaction mixture under reduced pressure was added to water (50 ml) and extracted with chloroform (150 ml×2). The extract solution was washed with 10% sulfuric acid solution and successively with water, further was washed with saturated sodium bicarbonate aqueous solution and successively with water and was dried. The residue obtained by removing the solvent from the extract solution was purified by silica gel column chromatography (ethyl acetate) to give benzyloxycarbonyl derivative of the titled compound (1.27 g; yield 77.4%). The derivative (1.27 g) was dissolved in a mixture of ethyl acetate (80 ml) and ethanol (80 ml), and 10% palladium-carbon (0.13 g) was added and the mixture was stirred overnight under hydrogen at room temperature. The reaction mixture was filtered and the filtrate was concentrated. The residue obtained was purified by silica gel column chromatography (chloroform:methanol=95:5) and recrystallized from ether to give the titled compound (0.39 g; yield 45.7%). 
     Melting Point: 196° to 199° C. 
     IR Spectrum (KBr) cm -1  : 1695, 1600 (C═O). 
     NMR Spectrum (DMSO-d 6 ) δppm: 2.68 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.62 (8H, s, &gt;NCH 2  CO--×4), 5.77 (4H, s, &gt;NCH 2  O--×2), 6.55 (4H, d, J=9 Hz, aromatic H), 7.57 (4H, d, J=9 Hz, aromatic H). 
     To a solution of the thus obtained titled compound (0.88 g, 1.6 m mol) in pyridine (20 ml), methanesulfonyl chloride (0.25 ml, 3.2 m mol) was added gradually and the reaction mixture was stirred for 1 hour at 0° C. and successively 2 hours at room temperature. The residue obtained by removing the solvent from the reaction mixture under reduced pressure was added to water (100 ml) and extracted with ethyl acetate (150 ml). The extract solution was washed with 10% sulfuric acid solution and successively with water, further was washed with saturated sodium bicarbonate aqueous solution and successively with water and was dried. The residue obtained by removing the solvent from the extract solution was purified by silica gel column chromatography (ethyl acetate) to give 1,2-bis[4-(p-methanesulfonylaminobenzoyloxymethyl)-3,5-dioxopiperazin-1-yl]ethane (0.43 g; yield 38%). 
     Melting Point: 95° to 105° C. 
     IR Spectrum (KBr) cm -1  : 1700, 1600 (C═O). 
     NMR Spectrum (DMSO-d 6 ) δppm: 2.68 (4H, s, &gt;NCH 2  CH 2  N&lt;), 3.10 (6H, s, --SO 2  CH 3  ×2), 3.63 (8H, s, &gt;NCH 2  CO--×4), 5.85 (4H, s, &gt;NCH 2  O--×2), 7.28 (4H, d, J=9 Hz, aromatic H), 7.86 (4H, d, J=9 Hz, aromatic H).