NMR manifestations and molecular dynamics modeling of chiral recognition of α-pinenes by α-cyclodextrin

Abstract

NMR manifestations of chiral recognition of α-pinene enantiomers by α-cyclodextrin in D2O have been observed in both proton and carbon spectra. The largest splittings in the former spectra amounted to 0.06ppm while an unusually high value of 1.3ppm was found in the corresponding carbon spectra. Different mobilities of the enantiomeric guests in the host cavities have been established in D2O using NOE and ROESY techniques. Molecular dynamics simulations indicated the instability of the complexes of 1:1 stoichiometry both in vacuum and water. However, the corresponding calculations for the 1:2 stoichiometry in vacuum gave incorrectly larger stability of the complex with the (1R,5R)-enantiomer of α-pinene. Long simulations of 3.5ns in water reproduce the stability order of the diastereomeric complexes.