Synthesis and biological evaluation of 2 ',3 '-didehydro-2 ',3 '-dideoxy-5-fluorocytidine (D4FC) analogues: Discovery of carbocyclic nucleoside triphosphates with potent inhibitory activity against HIV-1 reverse transcriptase

The discovery of a novel cytosine nucleoside, beta-D-2',3'-didehydro-2',3'- dideoxy-5-fluorocytidine (D-D4FC), as a potent antihuman immunodeficiency v irus (HIV) agent led us to synthesize a series of analogues and derivatives of beta-D-D4FC that could be more selective and also possess increased gly cosidic bond stability. The synthesized D-D4FC analogues were evaluated for anti-HIV-1 activity, anticancer activity, and cytotoxicity in various cell s. The biological data demonstrated that the 5-substitution of beta-D-D4FC with bromine (6c) and iodine (6d) resulted in the loss of antiviral activit y, and the alpha-D anomer (7a) of D-D4FC was also devoid of activity. The E i-fluorouracil analogues (6b and 7b) of D-D4FC were less potent and more cy totoxic than the parent compound, whereas the P-L-D4FU (II) showed both pot ent anti-HIV-l activity and cytotoxicity. N-4- and 5'-O-acyl derivatives (1 7, 15a-c) of beta-D-D4FC exhibited comparable antiviral activity to beta-D- D4FC. In contrast, the N-4-isopropyl derivative (20) of beta-D-D4FC was not active against HIV-1, even at 100 mu M. The carbocyclic analogues (26a,b) of D4FC demonstrated weak activity against HIV-1 and no toxicity in various cells. The triphosphates (27a,b) of the carbocyclic nucleosides demonstrat ed potent inhibitory activity against recombinant HIV-1 reverse transcripta se at submicromolar concentrations. Of the compounds tested as potential an ticancer agents, beta-D-, alpha-D-, and beta-L-D4FU (6b, 7b, 11) showed inh ibitory activity against rat glioma and modest activity against human lung carcinoma, lymphoblastoid, and skin melanoma cells.