d- and l-2′3′-Didehydro-2′3′-Dideoxy-3′-Fluoro-Carbocyclic Nucleosides: Synthesis Anti-HIV Activity and Mechanism of Resistance

摘要

Introducing 2′-fluoro substitution on the 2′,3′-double bond in carbocyclic nucleosides has provided biologically interesting compounds with potent anti-HIV activity. As an extension of our previous works in the discovery of anti-HIV agents, d- and l-2′,3′-unsaturated 3′-fluoro carbocyclic nucleosides were synthesized and evaluated against HIV-1 in human peripheral blood mononuclear (PBM) cells. Among the synthesized l-series nucleosides, compounds >18, >19, >26, >28 exhibited moderate antiviral activity (EC50 7.1 μM, 6.4 μM, 10.3 μM and 20.7 μM, respectively), while among the d-series, the guanosine analogue (>35, d-3′-F-C-d4G) exhibited the most potent anti-HIV activity (EC50 0.4 μM, EC90 2.8 μM). However, the guanosine analogue >35 was cross-resistant to the lamivudine-resistant variants (HIV-1M184V). Molecular modeling studies suggest that hydrophobic interaction as well as hydrogen bonding stabilize the binding of compound >35 in the active site of wild type HIV reverse transcriptase (HIV-RT). In the case of l-nucleosides, these two effects are opposite which results in a loss of binding affinity. According to the molecular modeling studies, cross-resistance of d-3′-F-C-d4G (>35) to M184V mutant may be caused by the realignment of the primer and template in the HIV-RTM184V interaction, which destabilizes the RT-inhibitor triphosphate complex, resulting in a significant reduction in anti-HIV activity of the d-guanine derivative >35.