Assignment of the 1H, 19F, and 13C NMR spectra of 2-deoxy-2-fluoro- d-ribose and characterisation of the isomeric equilibrium

Abstract

The assignment of the 1H, 19F, and 13C NMR chemical shifts and coupling constants of 2-deoxy-2-fluoro- d-ribose, an important intermediate in the synthesis of antiviral nucleoside drugs, is reported and the NMR spectra are used to determine the proportions of the pyranose and furanose forms together with the anomeric ratios in acetone- d 6 solution. The β-pyranose isomer is shown to exist at equilibrium with both 4 C 1 and 1 C 4 conformations in approximately equal proportions in fast exchange. The α-pyranose isomer at equilibrium is predominantly in the 4 C 1 form but the 1C 4 conformer is also present in solution, the two forms being in intermediate exchange on the 19F NMR timescale but in fast exchange on the 1H and 13C NMR timescales. For both the pyranose and furanose forms, the β-anomer predominates. The results are similar to those for d-ribose.