It is a nucleoside that can be used to treat or prevent virus infection, especially dengue virus, yellow fever virus, West Nile virus, Japanese encephalitis virus, lice transmitted encephalitis virus, Kunjin virus, Murray Valley encephalitis and St. Louis encephalitis, Omsk haemorrhagic fever virus, bovine viral diarrhea virus, Zika virus and hepatitis C virus,Or the salt acceptable for prescription B selected from the group containing formula residues (2) and (3)；R1 is a formula compound (4)；X is r8308； 7491c-c (o) - o-ch-832222-o r83080-o-c (o)；Q is o or s； Z is hydrogen, or other formula (5)；R² is selected from the group consisting of hydrogen, C₁₋₆ alkyl,C₁₋₆ haloalkyl,a. In c833218331c833248c833248pt, halogen or hydrocarbyl is used instead of phenyl；R³ is H or C₁₋₄ alkyl；O r 2 and R 3 are held together, and the fixed carbon atoms form a cyclo-c 83231；R⁴ is selected from the group consisting of hydrogen, C₁₋₈ alkyl optionally substituted by halogen, -CH₂OC (O) C₁₋₄ alkyl or C₁₋₄ alkoxy,a C₃₋₇ cycloalkyl optionally substituted by halogen, a phenyl optionally substituted by halogen or C₁₋₄ alkyl,a C₁₋₄-phenyl alkyl in which the phenyl is optionally substituted by halogen or C₁₋₄ alkyl and 4- to 7-membered heterocycle containing 1 to 3 heteroatoms selected from N, S, and O, wherein said heterocycle it is optionally substituted by one or more halogen, or C₁₋₄ alkyl；R8308； (74919) replaced by halogen, halogen c8321c83318324；C₁₋₄ alkoxy,a. Halogenated tar c83218c8331248a or c83218c8331248a；R⁵ is hydrogen or -C (O) C₁₋₄ alkyl；R⁶ is hydrogen or -C (O) C₁₋₄ alkyl；O r83099 and r8310 are added together to form a 5-member cyclic carbonate； r8311s is hydrogen or other formula (6)；R831222 is hydrogen, fluorine and chlorine, o-ch8323；R⁹ is hydrogen or halogen； R¹⁰ is -alkoxy C₁₋₄,C₁₋₄ or -NH₂ haloalkoxy.Es un nucleósido ramificado en 2 útil para el tratamiento o la prevención de infecciones virales, particularmente el virus del dengue, virus de la fiebre amarilla, virus del Ni
