SYNTHESIS OF 1-(2-DEOXY-β-D-RIBOFURANOSYL)-2,4-DIFLUORO-5-SUBSTITUTED-BENZENES^*: “THYMINE REPLACEMENT” ANALOGS OF THYMIDINE FOR EVALUATION AS ANTICANCER AND ANTIVIRAL AGENTS

Abstract

A group of unnatural 1-(2-deoxy-β-D-ribofuranosyl)-2,4-difluoro-benzenes having a variety of C-5 two-carbon substituents [−C≡C−X, X = I, Br; −C≡CH;(E)−CH=CH−X, X = I, Br; −CH=CH₂; −CH₂CH₃; −CH(N₃) CH₂Br], designed as nucleoside mimics, were synthesized for evaluation as anticancer and antiviral agents. The 5-substituted (E)−CH=CH−I and −CH₂CH₃ compounds exhibited negligible cytotoxicity in a MTT assay (CC₅₀ = 10⁻³ to 10⁻⁴ M range), relative to thymidine (CC₅₀ = 10⁻³ to 10⁻⁵ M range), against a variety of cancer cell lines. In contrast, the C-5 substituted −C≡C−I and −CH(N₃)CH₂Br compounds were more cytotoxic (CC₅₀ = 10⁻⁵ to 10⁻⁶ M range). The −C≡C−I and −CH₂CH₃ compounds exhibited similar cytotoxicity against non-transfected (KBALB, 143B) and HSV-1 TK⁺ gene transfected (KBALB-STK, 143B-LTK) cancer cell lines expressing the herpes simplex virus type 1 (HSV-1) thymidine kinase gene (TK⁺). This observation indicates that expression of the viral TK enzyme did not provide a gene therapeutic effect. The parent group of 5-substituted compounds, that were evaluated using a wide variety of antiviral assay systems [HSV-1, HSV-2, varicella-zoster virus (VZV), vaccinia virus, vesicular stomatitis, cytomegalovirus (CMV), and human immunodeficiency (HIV-1, HIV-2) viruses], showed that this class of unnatural C-aryl nucleoside mimics are inactive and/or weakly active antiviral agents.

ACKNOWLEDGMENTS

We are grateful to the Canadian Institutes of Health Research (Medical Research Council of Canada) Grant No. MT-14480 for financial support of this research, and to the Alberta Heritage Foundation for Medical Research for a fellowship to one of us (Z.-X.W.). The experiments done at the Rega Institute were supported by the Fonds voor Wetenschappelijk Onderzoek (FWO)-Vlaanderen Krediet No. 9.0104.98, and the Geconcerteerde Onderzoeksacties (GOA)-Vlaamse Gemeenschap contract No. 2000/12. We thank Ann Absillis, Anita Camps, Frieda De Meyer, Lizette van Berckelaer, Lies Vandenheurck, and Anita Van Lierde for excellent technical assistance.

Notes

^*Nucleoside-like numbering is used by analogy to nucleoside nomenclature.