Furanoses are an important group of natural saccharides as well as the components of crucial biomolecules such as nucleic acids. Contrary to pyranoses, they exhibit much larger inherent flexibility which amplifies the difficulty in determining their conformational preferences. We carried out a series of molecular dynamics simulations oriented at systematic analysis of conformational properties of unfunctionalized furanose monosaccharides (all members of d-aldopento- and d-aldotetrofuranoses). The results concern the description of the influence of the ring substituents (with respect of their type, location and orientation) on the geometry of the furanose ring. The main energetic contributions to the barriers on the pseudorotation path are associated with the following types of interactions: (i) unfavorable interactions between uniformly oriented vicinal ring substituents; (ii) unfavorable syn-axial interactions between uniformly oriented non-vicinal ring substituents; (iii) endo-anomeric effect. The interactions resulting from the presence of the particular ring substituents are not additive and cannot be used to obtain the pseudorotational profiles. The orientation of the hydroxymethyl group and the conformation of the ring are not mutually correlated. Contrary, the ring conformational preferences are correlated with the orientation of the lactol group via the influence of the exo-anomeric effect. Finally, analogously to pyranoses, also in the case of furanoses, the intramolecular hydrogen bonding does not play any essential role in conformational properties of monosaccharides.Communicated by Ramaswamy H. Sarma.
Keywords: Furanoses; free energy; hydrogen bonding; molecular dynamics; pseudorotation.