Synthesis and antiviral evaluation of unnatural beta-L-enantiomers of 3 '-fluoro- and 3 '-azido-2 ',3 '-dideoxyguanosine derivatives

3'-fluoro-2',3'-dideoxy- (3) and 3'-azido-2',3'-dideoxy- (4) beta-L-ribofur anonucleoside derivatives of guanine have been synthesized and their antivi ral properties examined. All these derivatives were regioselectively and st ereospecifically prepared by glycosylation of 2-N-acetyl-6-O-(diphenylcarba moyl)guanin 5 with a suitable peracylated L-xylo-furanose sugar 6, followed by appropriate chemical modifications. The prepared compounds were tested for their activity against HIV and HBV viruses, but they did not show signi ficant activity.