The present invention provides a compound of formula A: or a pharmaceically acceptable salt thereof, wherein B, Q, R1, R5, R6, R7, R8 and Z are detined herein, which is a 2’-branched nucleoside useful for the treatment or prevention of viral infections, particularly dengue virus, yellow fever virus, West Nile virus, Japanese encephalitis virus, tick-borne encephalitis virus, Kunjin virus, Murray Valley encephalitis, St Louis encephalitis, Omsk hemorrhagic fever virus, bovine viral diarrhea virus, Zika virus and Hepatitis C virus.本發明提供式A化合物,或其醫藥上可接受之鹽,其中B、Q、R1、R5、R6、R7、R8及Z係定義於本文中,其係2’-支鏈核苷,可用於治療或預防病毒感染,特別是登革熱病毒(dengue virus)、黃熱病毒、西尼羅河病毒(West Nile virus)、日本腦炎病毒、壁蝨傳播的腦炎病毒、庫京病毒(Kunjin virus)、墨累溪谷腦炎(Murray Valley encephalitis)、聖路易腦炎(St Louis encephalitis)、鄂木斯克出血熱病毒(Omsk hemorrhagic fever virus)、牛病毒性腹瀉病毒、寨卡病毒(Zika virus)及C型肝炎病毒感染。
