Regio- and stereoselective synthesis of carbocyclic 2',3'-dideoxy-3'-fluoro nucleosides as potential antiviral agents

The synthesis and antiviral activity of racemic carbocyclic 2',3'-dideoxy-3'-fluoro nucleosides are reported. Carbocyclic 2',3'-dideoxy-3'-fluoro nucleosides were obtained from the 3-fluoro cyclopentane derivative 4, which was prepared by two methods. The SN2-displacement of the hydroxyl group of (+/-)-(1 beta, 2 alpha, 3 beta, 4 beta)-4-acetamido-2-fluoro-3-hydroxycyclopentylmethyl acetate (1) with Ph3P-I2 followed by tin hydride reduction afforded the 3-fluoroamino alcohol derivative 3. Alternatively, the protected fluoroamino alcohol 3 was prepared by regio- and stereoselective bromo-fluorination of cis-4 beta-acetamidocyclopent-2-enemethyl acetate (5) with hydrogen fluoride-pyridine/N-bromosuccinimide followed by tin hydride reduction to remove the bromine atom. Carbocyclic 2',3'-dideoxy-3'-fluoroguanosine (14) thus obtained was moderately active against herpes simplex virus in vitro.