Abstract: To provide an easy and practical iron ion removal method, as a method for purifying P1,P4-di(uridine 5?-)tetraphosphate from a solution containing iron ions. Purification is performed by a purification method including a method for purifying P1,P4-di(uridine 5?-)tetraphosphate by removing iron ions from an aqueous solution or hydrophilic solvent solution containing P1,P4-di(uridine 5?-)tetraphosphate and iron ions, including (1) a step of purification using a chelating resin packed column, and (2) a step of adjusting the pH of the solution after said purification step using the chelating resin packed column to 5.5 or less, and then crystallizing P1,P4-di(uridine 5?-)tetraphosphate, or a step of treating the solution after said purification step using the chelating resin packed column with zinc chloride-activated activated carbon.

Abstract: [Problem] Provided is a method for easily and stably storing crystals of P1,P4-bis(5?-uridyl)tetraphosphate for a long term. [Solution] A method for storing packed crystals of P1,P4-bis(5?-uridyl)tetraphosphate or a pharmaceutically acceptable salt thereof, wherein one of the following storage conditions (1) to (3): (1) a storage temperature of 0° C. or more and less than 25° C.; (2) a storage temperature of 25° C. or more and less than 40° C. and a crystal pH of 4.5 to 8.0; and (3) a storage temperature of 40° C. or more and less than 60° C. and a crystal pH of 5.0 to 6.4 is selected and the crystals of P1,P4-bis(5?-uridyl)tetraphosphate or the pharmaceutically acceptable salt thereof are stored under the selected condition.

Abstract: To provide an easy and practical iron ion removal method, as a method for purifying P1,P4-di(uridine 5?-)tetraphosphate from a solution containing iron ions. Purification is performed by a purification method including a method for purifying P1,P4-di(uridine 5?-)tetraphosphate by removing iron ions from an aqueous solution or hydrophilic solvent solution containing P1,P4-di(uridine 5?-)tetraphosphate and iron ions, including (1) a step of purification using a chelating resin packed column, and (2) a step of adjusting the pH of the solution after said purification step using the chelating resin packed column to 5.5 or less, and then crystallizing P1,P4-di(uridine 5?-)tetraphosphate, or a step of treating the solution after said purification step using the chelating resin packed column with zinc chloride-activated activated carbon.

Abstract: [Problem] Provided is a method for easily and stably storing crystals of P1, P4-bis(5?-uridyl)tetraphosphate for a long term. [Solution] A method for storing packed crystals of P1, P4-bis(5?-uridyl)tetraphosphate or a pharmaceutically acceptable salt thereof, wherein one of the following storage conditions (1) to (3): (1) a storage temperature of 0° C. or more and less than 25° C.; (2) a storage temperature of 25° C. or more and less than 40° C. and a crystal pH of 4.5 to 8.0; and (3) a storage temperature of 40° C. or more and less than 60° C. and a crystal pH of 5.0 to 6.4 is selected and the crystals of P1, P4-bis (5?-uridyl) tetraphosphate or the pharmaceutically acceptable salt thereof are stored under the selected condition.

Abstract: The present invention relates to a novel 1-.beta.-D-arabinofuranosyl-(E)-5-(2-halogenovinyl)uracil derivative represented by the following formula (I), whose concentration in blood as XVAU can be kept high for many hours when it is administered orally.The present invention also relates to an antiviral agent comprising as an active ingredient the compound of the present invention.Further, the present invention relates to a method for treating viral diseases which comprises administering to a patient with a viral disease a safe and effective amount of the compound of the present invention. ##STR1## wherein X represents a halogen; and R.sup.1, R.sup.2, and R.sup.3, which may be the same or different, each represent a hydrogen atom, a lower alkyl group or an aralkyl group, provided that R.sup.1, R.sup.2 and R.sup.3 are not hydrogen at the same time.