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

NMR manifestations of chiral recognition of alpha-pinene enantiomers by alp ha-cyclodextrin in D2O have been observed in both proton and carbon spectra . The largest splittings in the former spectra amounted to 0.06 ppm while a n unusually high value of 1.3 ppm was found in the corresponding carbon spe ctra. Different mobilities of the enantiomeric guests in the host cavities have been established in D2O using NOE and ROESY techniques. Molecular dyna mics simulations indicated the instability of the complexes of 1:1 stoichio metry both in vacuum and water. However, the corresponding calculations for the 1:2 stoichiometry in vacuum gave incorrectly larger stability of the c omplex with the (1R,5R)-enantiomer of alpha-pinene. Long simulations of 3.5 ns in water reproduce the stability order of the diastereomeric complexes. (C) 2000 Elsevier Science B.V. All rights reserved.