Direct Correlation between Complex Conformation and Chiral Discrimination upon Inclusion of Amino Acid Derivatives by β- and γ-Cyclodextrins

A correlation between the conformation and chiral recognition characteristics of a series of modified amino acid complexes with beta- and gamma-cyclodextrins has been determined, using titration microcalorimetry and (1)H NMR techniques. The enantiomeric discrimination (D or L) is found to be dependent on the adoption of one of two distinct conformations. With the magnitude of the chiral discrimination (K(D)/K(L)) arising from the guest's depth of penetration into the host's cavity.