1H and (13)C NMR and Molecular Dynamics Study of Chiral Recognition of Camphor Enantiomers by alpha-Cyclodextrin.
1H and (13)C NMR spectra of the complexes of camphor enantiomers with alpha-cyclodextrin in D(2)O manifest splittings due to chiral recognition. The complexes were found to be of 1:2 guest-to-host stoichiometry. Free energies of the complex formation obtained from (1)H NMR titration data are equal to -7.95 +/- 0.09 kcal mol(-)(1) for the complex with (1S,4S)- and -7.61 +/- 0.06 kcal mol(-)(1) for that with (1R,4R)-enantiomer. Thus, the free energy difference between the complexes is equal to 0.34 +/- 0.11 kcal mol(-)(1), with the complex involving the (1S,4S)-camphor more stable. A strong positive cooperativity of the guests binding has been found. In agreement with experimental results, molecular dynamics simulations yielded greater stability of the complex with (1S,4S)-camphor. However, they reproduced only qualitatively the experimental trend since the corresponding difference in average energies obtained from molecular dynamic simulations carried out in a water solution is equal to 5 kcal/mol with the CVFF force field.
Dodziuk
Helena
H
Institute of Organic Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Kasprzaka 44, Poland, Institute of Biochemistry and Biophysics, Warsaw, Pawinskiego 5a,Poland, and University of Sheffield, Sheffield, S3 7HF, U.K.
Ejchart
Andrzej
A
Lukin
Oleg
O
Vysotsky
Myroslav O.
MO