Structure and theoretical NMR chemical shifts of modified cyclodextrins †

Abstract

Structural (geometries) and spectroscopic (NMR chemical shifts) characterization has been performed for a series of modified α- and β-cyclodextrins (CD), using the density functional theory (B3LYP/6-31G*) in combination with the GIAO method for calculating of the 13C and 1H chemical shifts. The compounds studied corresponded to the functionalized primary hydroxy group at C-6 (R=H, F, Cl, SH) for all the sugar moieties (per-substituted CDs) in the α- and β-CDs. Comparisons between experimental and calculated δ H and δ C chemical shifts yielded a good agreement for the DFT geometries. Furthermore, the GIAO-DFT methods proved to be a reliable tool in the assignments of the experimental NMR spectra. Finally, the 3 J H,H vicinal coupling constants were also estimated according with the Haasnoot–Leeuw–Altona equation and the results were compared with experimental data.