2',3'-dideoxy-beta-L-cytidine (beta-L-DDC) and its 5-fluoro derivative (beta-L-5-F-DDC) have been stereospecifically synthesized by a multi-step reaction sequence from L-xylose and their anti-HIV properties examined. Among these two L-enantiomers, the hitherto unknown beta-L-5-F-DDC emerged as a potent anti-HIV-1 and HIV-2 compound in different cell culture systems, with selectivity indices similar or superior to those of the currently licensed drug DDC which has the natural beta-D configuration.