Synthesis and antiviral activity of 2'-fluorohexopyranosyl nucleosides

2'-Fluorohexopyranosyl nucleosides 1a and 1b which contained a bioisosteric double bond and a fluorine were synthesized in 12 steps, starting from D-galactose. During diethylaminosulfur trifluoride (DAST) fluorination, retention of stereochemistry was observed through the participation of methoxy or chloro group at the 6-position of the purine base. The final nucleosides 1a and 1b were found to be inactive against HIV-1 and HSV-1,2.