Comparison between DFT- and NMR-based conformational analysis of methyl galactofuranosides

Abstract Galactofuranose (Gal f ) residues are found in a number of microbial polysaccharides, and knowledge of their conformation is key for developing a molecular-level understanding of their biological roles. To this end, we studied 180 conformations of methyl α- and β-Gal f in aqueous solution (COSMO solvation model) using density functional theory (DFT). We compare the calculated low energy conformations to those determined from the program PSEUROT using 1 H NMR data. The lowest energy ring conformation for methyl α-Gal f is 2 E , and this conformer is also the major solution conformation obtained by NMR spectroscopy. For methyl β-Gal f , 4 E is the lowest energy ring conformation; however, DFT results do not agree with the solution NMR spectroscopic results. Additionally, we developed Gal f -specific Karplus-like equations from these conformations.