Carbocyclic analogues of 5-fluorouracil nucleosides

The carbocyclic analogues of 5-fluoro-2'-deoxyuridine (5-FdUrd, 1), 5-fluorouridine, and 5-fluoro-3 alpha-deoxyuridine were prepared by fluorination of the uracil nucleoside analogues with elemental fluorine. The 5-FdUrd analogue (C-5-F-2'-dUrd, 6) was enzymatically phosphorylated to the analogue of 5-FdUrd 5'-phosphate and inhibited the incorporation of 2'-deoxyuridine into DNA of murine colon 26 tumor cells and L-1210 cells in culture. Biochemical studies also indicated that C-5-F-2'-Urd (6) was a less potent inhibitor of DNA synthesis in tumor cells than was 5-FdUrd (1). C-5-F-2'-dUrd was cytotoxic (ED50 = 2.5 mcg/mL) to L-1210 cells in culture; the other two analogues were less cytotoxic. C-5-F-2'-dUrd was inactive--or, at best, borderline active--in tests against P-388 leukemia in vivo.