Disclosed herein are nucleosides, nucleotides and nucleotide analogs, methods of synthesizing the same and methods of treating diseases and/or conditions such as a Picornavirus and/or Flaviviridae infection with one or more nucleosides, nucleotides and nucleotide analogs.本文揭示核苷、核苷酸及核苷酸類似物,其合成方法及使用一或多種核苷、核苷酸及核苷酸類似物治療諸如小核糖核酸病毒(Picornavirus)及/或黃病毒科(Flaviviridae)感染之疾病及/或病狀之方法。