Synthesis of β-Enantiomers of N 4 -Hydroxy-3′-Deoxy-Pyrimidine Nucleosides and Their Evaluation against Bovine Viral Diarrhoea Virus and Hepatitis C Virus in Cell Culture

Abstract

N⁴-Hydroxycytidine (NHC) was recently reported to have anti-pestivirus and anti-hepacivirus activity. It is thought that this nucleoside acts as a weak alternative substrate for the hepatitis C virus (HCV) polymerase. In addition to NHC, 3′-deoxyuridine (3′-dU) was found to inhibit bovine diarrhoea virus (BVDV) production by 1 log₁₀ at 37.2 μM. These initial findings prompted the synthesis of β-D and β-L analogues of (i) base-modified 3′-deoxy-NHC; (ii) 3′-deoxyuridine; and 3′-deoxycytidine. The antiviral activity of these 42 nucleosides was evaluated against BVDV and HCV bicistronic replicon in cell culture. Among the NHC analogues, the antiviral activity observed for the β-L-3′-deoxy-5-fluoro-derivative 1-(3-deoxy-β-L-erythro-pentofuranosyl)-5-fluoro-4-hydrox-yaminopyrimidin-2(1H)-one and the β-D-3′-deoxy-5-iodo-derivative 1-(3-deoxy-β-D-erythro-pentofuranosyl)-5-iodocytosine in the replicon system (1 log₁₀ reduction at 100 μM) was due to the concomitant toxicity towards intracellular ribosomal RNA levels (CC₉₀ equal or lower than the EC₉₀). In conclusion, none of the newly synthesized derivatives exhibited enhanced antiviral activity compared to the parent nucleoside NHC.