Due to the high flexibility of the glucose units CDs can be described by many conformers. Recent advances in high-performance computing and hardware setups were used in order to describe the geometries and wavefunctions of the structures of some selected symmetrical conformers. The method SMD/M06-2X/6-31G(d,p) was found to accurately describe the conformers in terms of their bond distances and angles, as shown by a comparison with experimental X-ray diffraction geometries. Based on the theoretical thermodynamic data and NMR analysis the most populated conformers were selected.
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Gamboa-Carballo, J.J., Rana, V.K., Levalois-Grützmacher, J., Gaspard, S., Jáuregui-Haza, U. Structures and stabilities of naturally occurring cyclodextrins: a theoretical study of symmetrical conformers. J. Mol. Model (2017) 23: 318. https://doi.org/10.1007/s00894-017-3488-4