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

The assignment of the H-1, F-19, and C-13 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 beta-pyranose isomer is shown to exist at equilibrium with both C-4(1) and C-1(4) conformations in approximately equal proportions in fast exchange. The alpha-pyranose isomer at equilibrium is predominantly in the C-4(1), form but the C-1(4) conformer is also present in solution, the two forms bring in intermediate exchange on the F NMR timescale but in fast exchange on the H-1 and C-13 NMR timescales. For both the pyranose and furanose forms, the beta-anomer predominates. The results are similar to those for D-ribose.