Abstract:
2&#39;,3&#39;-Dideoxy-4-thio-uridine derivatives represented by a following general formula ##STR1## (wherein R indicates hydrogen or protecting groups such as acetyl group, benzoyl group, trityl groups, etc.), process for their preparation, antivirus agents used them as effective ingredients and therapeutic method and therapeutic drugs for virus diseases are disclosed.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to novel 2&#39;,3&#39;-dideoxy-4-thiouridine derivatives and a process for their preparation. 
     The compounds of the invention exhibit an excellent antivirus effect and are extremely useful also, for example, as a therapeutic drug for AIDS being a virus disease. 
     As a result of diligent investigations of an novel compounds having antivirus effect and being low in toxicity, the inventors have found that 2&#39;,3&#39;-dideoxy-4-thio-uridine and the derivatives thereof exhibit excellent antivirus effect and are extremely useful, for example, as a therapeutic drug for AIDS. 
     SUMMARY OF THE INVENTION 
     The invention is concerned in 2&#39;,3&#39;-dideoxy -4-thio-uridine derivatives represented by a following general formula [I], antiAIDS virus agents having these as effective ingredients and therapeutic method and therapeutic drugs for virus diseases such as AIDS etc. ##STR2## (wherein R indicates hydrogen or protecting groups such as acetyl group, benzoyl group, trityl group, etc.). 
     Further, the invention provides a process for the preparation of 2&#39;,3&#39;-dideoxy-4-thio-uridine derivatives represented by a following general formula [I&#39;] ##STR3## (wherein R&#39; indicates protecting groups such as acetyl group, benzoyl group, trityl group, etc.), characterized in that, with 2&#39;,3&#39;-dideoxy-uridine derivatives represented by a following general formula [II] ##STR4## (wherein R&#39; is same as described above), phosphorus pentasulfide is allowed to react in pyridine, and a process for the preparation of 2&#39;,3&#39;-dideoxy-4-thio-uridine represented by a following general formula [I&#34;] ##STR5## characterized in that 2&#39;,3&#39;-dideoxy-4-thio-uridine derivatives represented by the following general formula [I&#39;] ##STR6## (wherein R&#39; indicates protecting groups such as acetyl group, benzoyl group, trityl group, etc.), are hydrolyzed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows IR spectral chart of the compound of the invention and FIG. 2 shows UV spectral chart of the compound of the invention, respectively. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The compounds of the invention can be prepared easily through a following process using 2&#39;,3&#39;-dideoxy-uridine as a raw material. 
     Namely, using 2&#39;,3&#39;-dideoxy-uridine as a raw material, the hydroxyl group on 5&#39;-position is first protected by appropriate protecting groups such as acetyl group, benzoyl group, trityl group, etc. and then, by allowing to react with phosphorus pentasulfide in pyridine, it can be converted easily to corresponding 2&#39;,3&#39;-dideoxy-4-thio-uridine derivatives. By eliminating the protecting groups from these derivatives according to usual method, 2&#39;,3&#39;-dideoxy-4-thio-uridine being the compound of the invention is obtained in high yield. 
     When the 2&#39;,3&#39;-dideoxy-uridine derivatives being raw materials in the invention are allowed to react with phosphorus pentasulfide in pyridine solvent, the amount of phosphorus pentasulfide is desirable to be not less than 0.5 times mol, preferably 1 to 2 times mol to 2&#39;,3&#39;-dideoxy-uridine derivatives. In order to raise the yield of reaction further, it is preferable to add water to the reaction system and the amount of water to be added therefor is preferable to be 0.5 times mol to equivalent mol to phosphorus pentasulfide. Although the reaction proceeds without the addition of water, the reaction liquor becomes blackish brown and tarry substances are produced at this time resulting in the lowering in yield by several steps. The reaction completes by refluxing for 2 to 5 hours. After the completion of reaction, the pyridine solution is concentrated to distill off pyridine and the residue is extracted with chloroform. Thus, aimed 2&#39;,3&#39;-dideoxy-4-thiouridine derivatives can be obtained easily in a yield of not less than 95 %. Following this, by eliminating the protecting groups with alkali or acid according to usual method, 2&#39;,3&#39;-dideoxy-4-thio-uridine being the compound of the invention can be prepared in high yield and yet with ease. 
     The compound of the invention prepared in this way can be purified easily by ordinary purifying method, for example, column chromatographic method, recrystallizing method or combination of these. 
     Moreover, 2&#39;,3&#39;-dideoxy-uridine or the derivatives thereof being the raw materials can be obtained easily from uridine being a constituting ingredient of ribonucleic acid by known method. For example, in the method described in Chem. Pharm. Bull., 18(3), 554-560, 1970, uridine is treated with methanesulfonyl chloride in pyridine solvent to convert to 2&#39;,3&#39;,5&#39;-tri-O-methanesulfonyluridine and, by allowing this to react with sodium benzoate in acetamide or dimethylformamide solvent, 2,2&#39;-anhydro-1-(5&#39;-O-benzoyl-3&#39;-O-mesyl-β-arabinosyl)uracil is obtained. This is allowed to react with hydrogen bromide or acetyl bromide to convert to 5&#39;-O-benzoyl-2&#39;-bromo-2&#39;-deoxy-3&#39;-O-mesyluridine and then this is treated with palladium carbon or Raney nickel catalyst in ethanol under atmosphere of hydrogen to obtain 5&#39;-O-benzoyl-2&#39;,3&#39;-dideoxy-uridine in a yield of about 60% (Chem. Pharm. Bull., 18(3), 554-560, 1970). 
     In following, an example of the invention will be shown. 
     (1) PREPARING EXAMPLE 
     Into 50 ml of pyridine were dissolved 3.16 g of 5&#39;-benzoyl-2&#39;,3&#39;-dideoxy-uridine and 0.22 g of distilled water. Then, after added 2.67 g of phosphorus pentasulfide at room temperature under stirring, the mixture was refluxed for 3 hours. After the completion of reaction, the solids deposited by allowing to cool were collected by filtration, which were washed with small amount of pyridine. The pyridine filtrate obtained was concentrated to dryness and the residue was extracted with chloroform to separate 3.15 g of 5&#39;-benzoyl-2&#39;,3&#39;-dideoxy-4-thio-uridine(yield: 95%). 
     Then, this was dissolved into 40 ml of 2% methanol solution of sodium methoxide and the solution was refluxed for 1 hour. After the completion of reaction, the resultant liquor was neutralized with acetic acid, concentrated and separated for purification by means of column chromatography. The crystals thus obtained were purified again through the recrystallization from methanol to obtain 1.84 g of 2&#39;,3&#39;-dideoxy-4-thio-uridine (yield: 85%) with following physical properties. 
     Pale yellow needle-like crystals, Melting point: 121°-122° C. 
     NMR spectrum (DMSO--d6);δ 
     1.40-2.70 (4H, m, C 2  &#39; and C 3  &#39;--H) 
     3.80-4.30 (1H, m, C 5  &#39;--H) 
     5.10 (1H, t, C 5  &#39;--OH, disappeared with addition of D 2  O) 
     5.90 (1H, q, C 1  &#39;--H) 
     6.25 (1H, d, C 5  --H) 
     7.95 (1H, d, C 6  --H) 
     12.60 (1H, bs, N--H, disappeared with addition of D 2  O). 
     Elemental analysis : AsC 9  H 12  N 2  SO 3   
     Calculated C;47.36, H;5.30, N;12.27, S;14.05. 
     Observed C;47.46, H;5.33, N;12.12, S;14.08. 
     IR(KBr): As shown in FIG. 1. 
     UV(EtOH): As shown in FIG. 2. 
     (2) ANTIVIRUS TEST 
     EXAMPLE 1. 
     The antivirus effect of the compound of general formula [II&#39;]of the invention was ascertained according to the test method by Rowe et al (J. W. Virology 1970, 42, 1136). Results are shown in Table 1. 
     Virus: Moloney-murine leukemia virus. 
     Cells: SC-1. 
     
                       TABLE 1______________________________________Antivirus effectCompound tested   ED.sub.50 (μM)______________________________________Compound of invention             3.7AZT               0.02DDC               4.0______________________________________ (Note) ED: Effective dose μM: Micromol AZT: 3Azido-3deoxy-thymidine DDC: 2&#39;,3Dideoxy-cytidine 
    
     EXAMPLE 2. EFFECT ON ROUS SARCOMA VIRUS (RSV) 
     Employing cultured cells of the first generation (chick embryo fibroblast), RSV was infected for about 30 minutes. To this were added the samples diluted stepwise, and, after 4 to 7 days, which stage the transformation of cells due to RSV infection was inhibited at was judged under microscope. 
     
                       TABLE 2______________________________________Antivirus effect (on RSV)Compound tested Concentration (μg/ml)______________________________________Compound of invention            5-10DDC             0.5-1.0______________________________________ 
    
     EXAMPLE 3. 
     EFFECT ON HIV (HUMAN IMMUNODEFICIENCY VIRUS) 
     Employing MT-4 cells, HIV was infected for 1 hour at 37° C. To this were added the samples diluted stepwise, and, after 3 days, which stage the transformation of cells due to HIV infection was inhibited at was judged under microscope. 
     
                       TABLE 3______________________________________Antivirus effect (on HIV)Compound tested Concentration (μg/ml)______________________________________Compound of invention           10DDC             1.0______________________________________ 
    
     As shown in Table 1 through 3, the compound of the invention exhibits excellent antivirus effect similar to that of DDC. Based on this fact, it is evident that the compound of the invention is effective as a therapeutic drug for virus diseases such as AIDS etc. 
     As described above, in accordance with the invention, such compounds that are novel and that are excellent in the antivirus effect are provided. They are extremely effective, for example, as therapeutic drugs for virus diseases such as AIDS etc.