[New furano- and pyrrolo[2,3-d]pyrimidine nucleosides and their 5'-triphosphates: synthesis and biological...

Bicyclic furano[2,3-d]pyrimidine ribonucleosides were synthesized by Pd(0)- and CuI-catalyzed coupling of 5-iodouridine with terminal alkynes. The treatment of the resulting nucleosides with ammonia or methylamine solution in aqueous alcohol resulted in pyrrolo- and N(7)-methylpyrrolo[2,3-d]pyrimidine nucleosides. 5'-O-Triphosphates of bicyclic nucleosides were obtained by the treatment of the nucleosides with POCl3 in the presence of a "proton sponge." The 5'-O-triphosphates are not substrates for HCV RNA-dependent RNA polymerase, but are effective substrates for HCV RNA helicase/NTPase and did not inhibit ATP hydrolysis. Only 3-(beta-D-ribofuranosyl)-6-decyl-2,3-dihydrofuro-[2,3-d]pyrimidin-2-one showed a moderate anti-HCV activity in the HCV replicon system and efficiently inhibited replication of bovine viral diarrhea virus (BVDV) in KCT-cells, other compounds being inactive. None of the compounds were cytotoxic within the tested range of concentrations.