A New Synthetic Approach to the Clinically Useful, anti-HIV-Active Nucleoside, 9-(2,3-Dideoxy-2-fluoro-β-D-threo-pentofuranosyl)adenine (β-FddA). Introduction of a 2′-β-Fluoro Substituent via Inversion of a Readily Obtainable 2′-α-Flu

A convenient route to the anti-HIV active compound, 9-(2,3-dideoxy-2-fluoro-β-D-threo-pentofuranosyl)adenine (1, β-FddA) started with the facile introduction of fluorine at C2′ from the α-side of protected 9-(β-D-arabinofuranosyl)adenine (ara-A). Inversion of the stereochemistry at C2′ was accomplished via a stable vinyl intermediate (6), which underwent stereoselective reduction of the double bond to give the desired 2′-F-threo isomer with the opposite β-fluoro stereochemistry.