Synthesis and Biological Evaluation of New 5,6-dichlorobenzimidazole Nucleoside Derivatives

Novel 5,6-dichlorobenzimidazole nucleoside analogues structurally related to the well-known riboside DRB have been synthesized. The 1′,2′- trans nucleosides were prepared by condensation of peracylated sugars with 5,6-dichlorobenzimidazole, whereas the 1′,2′- cis β-D-arabinofuranosyl and β-D-lyxofuranosyl nucleosides were obtained by inversion of configuration on the sugar moiety. Chiral acyclic derivatives were stereospecifically prepared by ring-opening of furano- or pyrano-nucleosides by means of periodate oxidation, followed by borohydride reduction. The in vitro activities against a range of DNA and RNA viruses, as well as the cytotoxicities in human T-lymphocyte MT-4 cells, have been determined for these novel compounds and for DRB. No truly selective activity (i.e. clearly below the cytotoxic concentration) was observed against any of the viruses used. Some of the compounds, including DRB, were cytotoxic to MT-4 cells at CC 50 values of less than 10 μg ml −1 .