Synthesis and NMR spectra of tetrahydrofuran-2-13C

Relation between the NMR data and the pseudorotational free-energy profile for oxolane

The conformation of five-membered furanose rings is a crucial issue for the structural analysis of many biologically-relevant molecules, including DNA and RNA. Oxolane can be treated as a prototypical furanose, composed only of saturated unsubstituted ring. In spite of its structural simplicity, providing the accurate quantitative description of the oxolane conformational features remains a great challenge for both the experimental and theoretical techniques. Here we show the method of recovering the free-energy profiles describing the conformational equilibrium in the oxolane ring (i.e. pseudorotation) based on the experimentally-inferred NMR data ([Formula: see text] coupling constants). The results remain in agreement with the quantum-mechanical-based molecular dynamics simulations and emphasize the large contributions of all ring conformers, even those located at the free-energy barriers. This includes the significant populations of limiting 3T2/2T3 and OE/EO shapes. Our findings provide another example of a poor applicability of the two-state model, which is routinely applied to analyze the NMR data in terms of population of different ring conformers.

Total lineshape analysis of high-resolution NMR spectra powered by simulated annealing

The novel algorithm for a total lineshape analysis of high-resolution NMR spectra has been developed. A global optimization by simulated annealing has been applied that has allowed to overcome the main trouble of common approaches which had frequently returned solutions for local minima rather than for global ones. The algorithm has been verified for the four-spin test systems ABCD, and has been successfully used for analysis of experimental NMR spectra of proline. The approach has allowed to avoid a sophisticated manual setup of initial parameters and to conduct the analysis of complicated high-resolution NMR spectra nearly automatically.