Synthesis and Biological Evaluation of 1,3-Oxathiolane 5-Azapyrimidine, 6-Azapyrimidine, and Fluorosubstituted 3-Deazapyrimidine Nucleosides

(2R,5S)-5-Amino-2-[2-(hydroxymethyl)-1,3-oxathiolan-5-y1]-1,2,4-triazine-3(2H)-one (8) and (2R,5R)-5-amino-2-[2-(hydroxymethyl)-1,3-oxathiolan-5-y1]-1,2,4-triazine-3(2H)-one (9) have been synthesized via a multi-step procedure from 6-azauridine. (2R,5S)-4-Amino-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-y1]-1,3,5-triazine-2(1H)-one (11) and (2R,5R)-4-amino-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-y1]-1,3,5-triazine-2(1H)-one (12), and the fluorosubstituted 3-deazanucleosides (19-24) have been synthesized by the transglycosylation of (2R,5S)-1-{2-[[(tert-butyldiphenylsilyl) oxy]methyl]-1,3-oxathiolan-5-y1} cytosine (2) with silylated 5-azacytosine and the corresponding silylated fluorosubstituted 3-deazacytosines, respectively, in the presence of trimethylsilyl trifluoromethanesulfonate as the catalyst in anhydrous dichloroethane, followed by deprotection of the blocking groups. These compounds were tested in vitro for cytotoxicity against L1210, B 16 F 10 , and CCRF-CEM tumor cell lines and for antiviral activity against HIV-1 and HBV.