ASSIGNMENT OF THE H-1, F-19, AND C-13 NMR-SPECTRA OF 2-DEOXY-2-FLUORO-D-RIBOSE AND CHARACTERIZATION OF THE ISOMERIC EQUILIBRIUM

The assignment of the H-1, F-19, and C-13 NMR chemical shifts and coup ling constants of 2-deoxy-2-fluoro-D-ribose, an important intermediate in the synthesis of antiviral nucleoside drugs, is reported and the N MR spectra are used to determine the proportions of the pyranose and f uranose forms together with the anomeric ratios in acetone-d(6) soluti on. The beta-pyranose isomer is shown to exist at equilibrium with bot h C-4(1) and C-1(4) conformations in approximately equal proportions i n fast exchange. The alpha-pyranose isomer at equilibrium is predomina ntly in the C-4(1), form but the C-1(4) conformer is also present in s olution, the two forms bring in intermediate exchange on the F NMR tim escale but in fast exchange on the H-1 and C-13 NMR timescales. For bo th the pyranose and furanose forms, the beta-anomer predominates. The results are similar to those for D-ribose.