title: Structure-activity relationships of 2'-deoxy-2',2'-difluoro-L-erythro-pentofuranosyl nucleosides.
abstract: Following the recent discoveries that some L-nucleosides are more or equal potent than their D-counterparts, we synthesized 2'-deoxy-2',2'-difluoro-L-erythro-pentofuranosyl nucleosides as potential antiviral agents. The target compounds were synthesized via the key intermediates 7a or 7b from L-gulono gamma-lactone. Compound 2 was oxidatively cleaved and coupled with ethyl bromodifluoroacetate in the presence of activated zinc under Reformatsky conditions to obtain a diasteomeric mixture of 4(R) and 4(S), in a 4:1 ratio. The major 4(R) isomer was cyclized and treated appropriately to obtain the mesylate 8a or 8b, which was condensed with various silyl-protected pyrimidines. Condensation of the alcohol 7a or 7b with 6-chloropurine under Mitsunobu conditions afforded the 6-chlorpurine analogs 53a or 53b and 54a or 54b. Further treatment of the compounds 53a, 54a and 53b, 54b afforded the inosine and adenine derivatives 57-60, respectively. The condensation of 2-amino-6-chloropurine with compound 8a and subsequent treatment with 2-mercaptoethanol/sodium methoxide afforded the guanine analogs 63 and 64. All of the synthesized nucleosides 31-52, 57-60, 63, and 64 were evaluated for antiviral activity and for cellular toxicity. Adenine derivative 57 showed a moderate activity against HIV-1 in PBM cells (3.4 microM). None of the other compounds showed any significant activities against HIV-1, HBV, HSV-1, HSV-2, and toxicity in Vero, CEM, and PBM cell lines up to 100 microM. The X-ray structure of the 5-iodocytosine analog showed a 2'-exo/3'-endo conformation for the carbohydrate moiety, which is different from those of the biologically active compounds (-)-FTC and L-FMAU.
authors.affiliation: Department of Medicinal Chemistry, College of Pharmacy, University of Georgia, Athens 30602-2352, USA.
authors.forename: L P
authors.initials: LP
authors.lastname: Kotra
authors.forename: Y
authors.initials: Y
authors.lastname: Xiang
authors.forename: M G
authors.initials: MG
authors.lastname: Newton
authors.forename: R F
authors.initials: RF
authors.lastname: Schinazi
authors.forename: Y C
authors.initials: YC
authors.lastname: Cheng
authors.forename: C K
authors.initials: CK
authors.lastname: Chu
mesh_terms: D000998:Antiviral Agents / Q000737:chemistry* / Q000494:pharmacology*; D002478:Cells, Cultured; D015497:HIV-1 / Q000187:drug effects; D006515:Hepatitis B virus / Q000187:drug effects; D018259:Herpesvirus 1, Human / Q000187:drug effects; D018258:Herpesvirus 2, Human / Q000187:drug effects; D009705:Nucleosides / Q000737:chemistry* / Q000494:pharmacology*; D013057:Spectrum Analysis; D013329:Structure-Activity Relationship
chemical_list: D000998:Antiviral Agents; D009705:Nucleosides