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Abstract：
Upon reacting 3\',4\'-unsaturated cytosine (8 and 9) and adenine nucleosides (13 and 14) with XeF(2)/BF3 · OEt(2), the respective novel 3\',4\'-difluoro-3\'-deoxyribofuranosyl nucleosides (10-12 and 15-18) could be obtained. Formation of anti-adducts (11, 16 and 18) revealed that the fluorination involved oxonium ions as incipient intermediates. TBDMS-protected 3\',4\'-unsaturated adenosine provided the β-face adducts as sole stereoisomers whereas α-face-selectivity was observed with the TBDPS-protected adenosine 14. The evaluation of the novel 3\'-deoxy-3\',4\'-difluororibofuranosylcytosine-(19-21) and adenine nucleosides (22-25) against antitumor and antiviral activities revealed that 3\',4\'-difluorocordycepin (24) was found to possess anti-HCV activity. The SI of 24 was comparable to that of the anti-HCV drug ribavirin. However, sofosbuvir, FDA-approved novel anti-HCV drug, showed better SI value. Our finding revealed that the introduction of the fluoro-substituent into the 4\'-position of cordycepin derivatives decreased the cytotoxicity to the host cell with retention of the antiviral activity.
摘要：
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