Stereoselective synthesis of 3-fluorotetrahydrofuran-3-carboxylate derivatives via the intramolecular cyclization reaction of erythro- and threo-α-allylated α-fluoro-β-hydroxy esters

When isomerically pure erythro- and threo-α-allylated-α-fluoro-β-hydroxy carboxylic acid esters were subjected to the intramolecular cyclization reaction with iodine and pyridine at −15 °C to ambient temperature for 6–9 h, the corresponding 3-fluorotetrahydrofuran-3-carboxylate derivatives were obtained in good yields as isomeric mixtures of the ratio of 3A:3B=10–20:90–80 or 4C:4D=28–39:72–61, respectively.