title: l-2',3'-Didehydro-2',3'-dideoxy-3'-fluoronucleosides: synthesis, anti-HIV activity, chemical and enzymatic stability, and mechanism of resistance.
abstract: As antiviral nucleosides containing a 2',3'-unsaturated sugar moiety with 2'-fluoro substitution are endowed with increased stabilization of the glycosyl bond, it was of interest to investigate the influence of the fluorine atom at the 3'-position. Various pyrimidine and purine L-3'-fluoro-2',3'-unsaturated nucleosides were synthesized from their precursors, L-3',3'-difluoro-2',3'-dideoxy nucleosides, by elimination of hydrogen fluoride. In the L-3',3'-difluoro-2',3'-dideoxy nucleoside series, cytidine 16 and 5-fluorocytidine 18 analogues showed modest antiviral activity (EC(50) 11.5 and 8.8 microM, respectively) when evaluated against HIV-1 in human peripheral blood mononuclear (PBM) cells. In the 2',3'-unsaturated series, L-3'-fluoro-2',3'-didehydro-2',3'-dideoxycytidine 24 and 5-fluorocytidine 26 showed highly potent antiviral activity (EC(50) 0.089 and 0.018 microM, respectively) without significant cytotoxicity. The guanosine analogue 48 showed only marginal anti-HIV activity with some cytotoxicity (EC(50) 38.5 microM, and IC(50) 17.4, 58.4, 36.5 microM in PBM, CEM, and Vero cells, respectively). The cytidine 24 and 5-fluorocytidine 26 analogues, however, showed significantly decreased antiviral activity against the clinically important lamivudine-resistant variants (HIV-1(M184V)). Molecular modeling studies demonstrated that the 3'-fluoro atom of the L-3'-fluoro-2',3'-unsaturated nucleoside is within the hydrogen bonding distance with the amide backbone of Asp185, which favors the binding of the nucleoside triphosphate to the wild-type RT. This favorable binding mode, however, cannot be maintained when the triphosphate of 3'-fluoro 2',3'-unsaturated nucleoside binds to the active site of M184V RT because the bulky side chain of Val184 occupies the space needed for the nucleotide. The biological results suggest that, in addition to the sugar conformation, the base moiety may also play a role in their interaction with the M184V RT.
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, Athens, Georgia 30602, USA.
authors.forename: Youhoon
authors.initials: Y
authors.lastname: Chong
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Gumina
authors.forename: Judy S
authors.initials: JS
authors.lastname: Mathew
authors.forename: Raymond F
authors.initials: RF
authors.lastname: Schinazi
authors.forename: Chung K
authors.initials: CK
authors.lastname: Chu
mesh_terms: D019380:Anti-HIV Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D001665:Binding Sites; D002460:Cell Line; D024882:Drug Resistance, Viral; D004355:Drug Stability; D054303:HIV Reverse Transcriptase / Q000737:chemistry / Q000378:metabolism; D015497:HIV-1 / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D006801:Humans; D006860:Hydrogen Bonding; D019259:Lamivudine / Q000494:pharmacology; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000821:virology; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009705:Nucleosides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D017354:Point Mutation; D018894:Reverse Transcriptase Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013329:Structure-Activity Relationship
chemical_list: D019380:Anti-HIV Agents; D009705:Nucleosides; D018894:Reverse Transcriptase Inhibitors; D019259:Lamivudine; D054303:HIV Reverse Transcriptase