NMR Studies of Inclusion Complexes Formed by (R)-alpha-Lipoic Acid with alpha-, beta-, and gamma-Cyclodextrins

摘要

The structures of inclusion complexes of (R)-alpha-lipoic acid with alpha-, beta-, and gamma-cyclodextrin (CD) were constructed using restraints derived from ROESY spectra and MMFF94 molecular mechanics calculations. (R)-alpha-lipoic acid and alpha-CD generate a single stable inclusion complex, in which the 1,2-dithiolane ring of the (R)-alpha-lipoic acid is oriented toward the secondary hydroxy side of the alpha-CD. NMR data suggests that beta-CD produces two kinds of inclusion complexes with alpha-lipoic acid. Finally, gamma-CD yields 1:1 and 1:2 host/guest complexes with (R)-alpha-lipoic acid. The estimated structure of the 1:1 gamma-CD inclusion complex has the 1,2-dithiolane ring oriented toward the primary hydroxy side of the gamma-CD.