CONFORMATIONAL-ANALYSIS .19. CONFORMATIONAL-ANALYSIS OF 6-DEOXY-6-FLUORO-D-GLUCOSE (6DFG) IN SOLUTION

The conformation of D-glucopyranose and 6-deoxy-6-fluoro-6-glucose (6DFG) in solution, as determined by H-1 and F-19 NMR, is reviewed. The H-1 NMR spectra of alpha- and beta-methyl D-glucopyranosides and 6DFG in methanol, acetone, DMSO, and aqueous solution were acquired and fully analysed. A F-19 NMR spectrum of the methanol 6DFG solution, together with a H-1 COSY spectrum of alpha-6DFG in methanol, were recorded. Accurate analyses of the ABC and ABCX spectra produced by the -CHCH2OH and -CHCH2F moieities, respectively, were performed, and from the vicinal J(H-5,H-6) coupling constants the populations of the three possible staggered rotamers about the C-5-C-6 bond were calculated. The rotamer in which F is antiperiplanar to the ring O is particularly disfavoured, whereas the rotamer with F antiperiplanar to H-5 is most favoured. This general trend was seen for both pyranose anomers in all four solvents.