Conformational preferences in diglycosyl disulfides: NMR and molecular modeling studies.

The conformations of several β1→β1' diglycosyl disulfides were investigated by NMR and computational methods. Experimental data, such as NOEs, proton-proton and proton-carbon-13 coupling constants, measured for solutions in DMSO, are in good agreement with values obtained by MD simulations in explicit DMSO. The disulfide torsion angles (C1-S-S-C1') preferentially sample values close to either +90° or -90° (+g or -g) and appear as the main metric that determines the conformational behavior of these glycomimetics. There is more conformational freedom around the C1-S and C1'-S' bonds (Φ and Ω torsions, respectively) and population cluster analysis allowed to identify up to four allowed conformational regions for each of the +g or -g forms. Population analysis of the hydroxylic group rotamers, based on proton-proton and proton-carbon-13 couplings as well as on calculated hydrogen bonding statistics, did not reveal any significant intramolecular hydrogen bonds in DMSO solution.