the compounds of the present invention are 5 - halogenovinyl araump represented by the above formula ( i ) and pharmaceutically acceptable salts thereof . typical compounds are those wherein the halogen x is chlorine , bromine or iodine , particularly chlorine or bromine . examples of pharmaceutically acceptable salts are alkali metal salts such as sodium , potassium , and lithium , alkaline earth metal salts such as calcium and magnesium , and mono - and di - salts such as ammonium salts . as for the physicochemical properties of these compounds , the principal properties are shown in the synthesis examples set forth below for representative compounds . the 5 - halogenovinyl araump is improved to a great extent in solubility in aqueous solvents , as compared with 5 - halogenovinyl arau . for example , while the solubility of 1 - β - d - arabinofuranosyl -( e )- 5 -( 2 - bromovinyl ) uracil ( hereinafter abbreviated as bvau ) in water is 0 . 4 %, that of a disodium salt of 1 - β - d - arabinofuranosyl -( e )- 5 -( 2 - bromovinyl ) uracil - 5 &# 39 ;- phosphate ( hereinafter abbreviated as bvaup ) is as high as about 50 %. accordingly , particularly when this salt is used as an intravenous injection or a collyrium , the administration concentration thereof can be advantageously increased . the 5 - halogenovinyl araump was also found to be more potent in anti - herpes activity in vivo than the 5 - halogenovinyl arau . the 5 - halogenovinyl araump of the formula ( i ) can be prepared according to any method suitable for formation of the desired bonding or introduction of an atomic group . one suitable method comprises , as mentioned above , 5 &# 39 ;- phosphorylation of the 5 - halogenovinyl arau of the formula ( ii ). phosphorylation may be conducted according to a conventional method used for selective phosphorylation of the 5 &# 39 ;- hydroxyl group of a nucleoside . such a method , in general , comprises reacting a 5 - halogenovinyl arau with a phosphorylating agent in an organic solvent suitable for a selective phosphorylation . as a suitable solvent , a variety of organic solvents can be used , including hydrocarbons such as hexane , cyclohexane and benzene ; halohydrocarbons such as dichloromethane , chloroethane , chlorohexane and chlorobenzene ; phenols such as phenol , o -, m - and p - cresol and o - chlorophenol ; organic acid esters such as ethyl acetate , ethyl benzoate and methyl acrylate ; nitro compounds such as nitromethane , nitroethane , nitropropane and nitrobenzene ; nitriles such as acetonitrile , propionitrile , benzonitrile and malononitrile ; ethers such as ethyleneglycol dimethylether , ethyleneglycol diethylether , tetrahydrofuran and dioxane ; trialkyl phosphates such as trimethylphosphate and triethylphosphate . these solvents may be used alone or in admixture thereof , or may be used in admixture with an organic base such as pyridine and picoline or an organic amine - inorganic acid salt such as pyridine hydrochloride and picoline hydrobromide . as a phosphorylating agent , a phosphorus halide type reagent such as phosphorus oxychloride , phosphorus trichloride , phenylphosphorus dichloride , morpholinophosphorus dichloride or partially hydrolyzed phosphorus oxychloride or a pyrophosphate type reagent such as pyrophosphoryltetrachloride may be used . as examples of a combination of these reagents and solvents , the combination of phosphorus oxychloride and a trialkylphosphate , and the combination of pyrophosphoryltetrachloride and phenol , are preferable . the reaction temperature is preferably about 0 ° c . to about room temperature , and the reaction time is preferably from several hours to some tens of hours . isolation and purification of 5 - halogenovinyl araump from the reaction mixture may be performed according to any method , which is not particularly limited , and the method conventionally used for purification of a nucleotide may suitably be employed . for example , it may be practiced by any desired selection or combination of the known purification methods such as adsorption chromatography using silica gel or an adsorption resin as a carrier , ion - exchange chromatography , and recrystallization . the 5 - halogenovinyl arau is a known substance as mentioned above and can be prepared by reacting a halogen with 1 - β - d - arabinofuranosyl - 5 - vinyluracil in an anhydrous polar solvent ( see japanese patent laid - open no . 87599 / 1981 ; u . s . patent application ser . no . 215 , 928 ( u . s . pat . no . 4 , 386 , 076 ); canadian patent application no . 367 , 108 ; spanish patent application no . 498 , 020 ; and european patent publication no . ep 31128 a1 ). a 5 - halogenovinyl araump of the formula ( i ), in spite of its high antiviral activity , exhibits little cytostatic action and therefore can advantageously be used as an effective component for an anti - dna virus agent . a 5 - halogenovinyl araump or its pharmaceutically acceptable salt may be used for prevention and therapy of dna virus infections , more specifically , various herpes diseases ( keratitis , skin infection , genital infection , encephalitis , etc .) and varicella and zoster infections . a 5 - halogenovinyl araump or its pharmaceutically acceptable salt should be contained in an effective amount in the anti - dna virus agent to be used for such a purpose . the route of administration and the form of preparation of the anti - dna virus agent comprising a 5 - halogenovinyl araump or its pharmaceutically acceptable salt should be determined according to the disease caused by a given dna virus . to be more specific , for example , in case of topical application on the skin , an ointment is suitable and is a representative form of preparation , while in case of topical application to the cornea , an ointment and a collyrium are suitable and are representative forms of preparations , respectively . the anti - dna virus agent may be administered in a dose which should be suitably determined by the attendant physician according to the severity of the disease based on a given dna virus . more specifically , for example , a collyrium with a concentration of 0 . 1 to 10 % and an ointment with a concentration of about 0 . 5 to 10 % is administered several times per day . in the case of orally administered preparations and injections , administration is performed in a dose of 0 . 5 to 10 g / body . one of the most important features of the compound ( i ) is that it has low toxicity or little cytostatic action . the ld 50 values of bvaup administered intraperitoneally and intravenously in mice are 1728 and 1610 mg / kg , respectively . the compound ( i ) exhibits generally high antiviral activity regardless of the species of the dna virus , but the magnitude of activity depends somewhat on the species of the objective dna virus . for example , according to the knowledge we have acquired hitherto , the compound ( i ) wherein x is bromine has an antiviral activity against the type 2 herpes ( hsv - 2 ) which is lower than that against the type 1 herpes ( hsv - 1 ) or vzv . as mentioned above , typical examples of the dna virus to be treated in the present invention are herpes virus and varicella - zoster virus . other than these , for example , against those dna viruses which will induce deoxypyrimidine nucleoside kinase after infection , the present compound ( i ) can be fully expected to exhibit anti - dna virus activity because it can be converted by this enzyme and the kinase in host cells to 5 - halogenovinyl arautp ( 1 - β - d - arabinofuranosyl -( e )- 5 -( 2 - halogenovinyl ) uracil triphosphate ) to inhibit specifically the viral dna synthesis . in order to indicate more fully the nature and utility of this invention , the following specific examples of practice are set forth , it being understood that these examples are presented as illustrative only and that they are not intended to limit the scope of the invention . after 3 . 49 g of bvau was dissolved in 50 ml of trimethylphosphate , the solution was cooled on ice and left to stand overnight with the addition of 2 . 8 ml of phosphorus oxychloride . the reaction mixture was poured into 500 ml of ice - water and adjusted to ph 7 . 0 with 40 % sodium hydroxide . the above neutralized solution was concentrated to dryness under reduced pressure , and the residue was dissolved in one liter of water and adsorbed onto a column of 500 ml of an adsorption resin diaion hp - 20 ( trade name of resin produced by mitsubishi kasei kogyo co ., ltd ., japan ). after washing with water , the column was subjected to elution with a 5 % aqueous methanol solution , and the eluate was adsorbed on a 100 - ml column of an ion - exchange amberlite ira68 ( formic acid form ) ( trade name , produced by rohm & amp ; haas co ., u . s . a . ), which step was followed by elution with 2n formic acid . the resulting eluate was concentrated to dryness under reduced pressure , and the residue was subjected to recrystallization from water to obtain 1 . 86 g of bvaup ( free form ) ( yield : 43 . 4 %). melting point ( m . p .) 190 °- 192 ° c . ( decomp .) uv absorption spectrum : λ max 0 . 01 n - naoh : 256 nm , 284 nm ( sh ) λ max 0 . 01 n - hcl : 251 nm , 293 nm elemental analysis ( for c 11 h 14 n 2 o 9 brp . 1 / 2h 2 o ): calculated value : c , 30 . 16 ; h , 3 . 45 ; n , 6 . 39 % experimental value : c , 30 . 19 ; h , 3 . 18 ; n , 6 . 30 % after 3 . 05 g of 1 - β - d - arabinofuranosyl -( e )- 5 -( 2 - chlorovinyl ) uracil ( hereinafter abbreviated as &# 34 ; cvau &# 34 ;) was dissolved in 30 ml of trimethylphosphate , the solution was cooled on ice and left to stand overnight with the addition of 1 . 9 ml of phosphorus oxychloride . the reaction mixture was poured into 500 ml of ice - water and adjusted to ph 7 . 0 with 40 % sodium hydroxide . the above neutralized solution was concentrated to dryness under reduced pressure , and the residue was dissolved in 300 ml of water and adsorbed onto a column of 150 ml of an adsorption resin diaion hp - 20 . after washing with water , the column was eluted with a 5 % aqueous methanol solution . a part of the wash water and the 5 % methanol eluate were combined and adsorbed on a 100 ml column of an ion - exchange amberlite ira68 ( formic acid form ), which step was followed by elution with 2n formic acid . the eluate was concentrated to dryness under reduced pressure , and the residue was subjected to recrystallization from water to obtain 2 . 13 g of 1 - β - d - arabinofuranosyl -( e )- 5 -( 2 - chlorovinyl ) uracil - 5 &# 39 ;- phosphate ( free form ) ( yield : 55 . 4 %). m . p . 226 °- 228 ° c . ( decomp .) uv absorption spectrum : λ max 0 . 01 n - naoh : 253 nm , 285 nm ( sh ) λ max 0 . 01 n - hcl : 247 nm , 293 nm according to the method of sidwell et al ( applied microbiology , 22 , ( 5 ), 797 ( 1971 )), with the use of human embryonic lung fibroblasts , the antiviral activities of bvaup and cvaup were tested , with bvau , cvau and 5 - iodo - 2 &# 39 ;- deoxyuridine ( idu ) as controls . the results were as shown in the following table . __________________________________________________________________________antiviral activity ; mic * and vr ** compounds testedbvaup cvaup bvau cvau iduvirusmic vr mic vr mic vr mic vr mic vr__________________________________________________________________________hsv - 1 - 0 . 032 3 . 8 0 . 032 3 . 7 0 . 032 3 . 7 0 . 032 3 . 7 3 . 2 2 . 4vr - 3 . sup . 1hsv - 2 - 32 1 . 1 320 0 . 5 32 1 . 1 100 0 . 7 3 . 2 2 . 2ms . sup . 2__________________________________________________________________________ * mic : minimum inhibitory concentration at which hsvinduced cytopathogenic effects were depressed more than 50 %; ** vr : virus rating . sup . 1 hsv1 - vr - 3 : herpes simplex virus type 1 strain vr3 . sup . 2 hsv2 - ms : herpes simplex virus type 2 strain ms ( 1 ) pigmented rabbits , weighing between 2 . 0 and 3 . 0 kg , were anesthetised with intravenous pentobarbital sodium ( 30 mg / kg ) and given a retrobulbar injection of 0 . 5 ml of 1 % procaine . for inoculation a suspension of the re strain of hsv ( type 1 ) was drawn into a fine glass capillary tube ( british journal of ophthalmology , vol . 63 , no . 6 , 425 - 428 ( 1979 ). after inoculation the eye was left open for 30 seconds and then the lids were closed with cellophane tape . the same procedure was repeated on the other eye . in one group of 3 rabbits the right eyes were treated with 1 % bvaup ointment and the left eyes with 1 % bvau ointment , or vice versa . in another group 3 eyes received no treatment as controls . the treatment was started 48 hours after inoculation and continued every 2 hours during the daytime 5 times a day for 4 days . the eyes were examined 48 hours after inoculation and then every 24 hours with a photo - slit lamp after applying 1 % bengal rose . each inoculation site was scored according to the extent of the circumference infected . the total daily score for each eye was calculated and expressed as a percentage of the score ( percentage score ) immediately before treatment . the therapeutic efficacies of bvaup and bvau against ulcerative herpetic keratitis were compared by calculating their average percentage scores . table______________________________________ effect total score ( lesiondrugs per eye % score inhibition ) ______________________________________control 97 . 0 100 01 % bvaup 44 . 7 46 . 1 53 . 91 % bvau 55 . 3 57 . 0 43 . 0______________________________________ ( 2 ) 0 . 3 % bvaup ointment and 3 % bvaup ointment were respectively prepared , and were subjected to the similar pharmacological test as shown in ( 1 ). table______________________________________ effect total score ( lesiondrugs per eye % score inhibition ) ______________________________________control 114 . 0 100 03 % bvaup 32 . 0 28 . 1 71 . 9control 88 . 7 100 00 . 3 % bvaup 54 . 7 61 . 7 38 . 3______________________________________