Synthesis and antiviral evaluation of novel conformationally locked nucleosides and masked 5'-phosphate derivatives thereof

As part of a programme towards evaluating the potential of conformationally locked 3′-deoxy- and 3′-azido-3′-deoxy-nucleoside derivatives as prodrugs of potential 5′-O-triphosphorylated anti-HIV drugs, novel nucleoside derivatives with locked N-type (north-type, C3′-endo) furanose conformation were prepared using convergent synthetic strategies. In addition, masked 5′-monophosphate derivatives of these, and of a conformationally restricted 3′-azido-3′-deoxynucleoside with E-type (eastern-type, O4′-endo) furanose conformation, were prepared in order to potentially circumvent the first phosphorylation step. However, neither the free 5′-hydroxy derivatives nor the masked 5′-monophosphates showed anti-HIV activity in MT-4 cells.