Complexation of Fluorinated Amino Acid Derivatives by β- and γ-Cyclodextrin in Aqueous Solution. A ¹⁹F Nuclear Magnetic Resonance Study

Abstract

A ¹⁹F n.m.r. study shows that the β-cyclodextrin complexes of deprotonated α-(p- fluorophenyl ) glycine, N-acetyl-α-(p- fluorophenyl ) glycine , deprotonated N-acetyl-α-(p- fluorophenyl ) glycine , and N-(p- fluorobenzoyl ) valine are characterized by stability constants KR/dm³ mol-¹ and Ks/dm³ mol-¹ =13±2 and 21±3, 34±1 and 35±2, 12±1 and 12± 1, and 84±2 and 93±2, respectively, where the first and second of each pair of values refers to the complex formed by the R and S enantiomers of the fluorinated amino acid derivatives, respectively, in 10% aqueous D₂O solution at 295.5 K and I = 0.10 mol dm-³. A comparison of these data and the associated ¹⁹F chemical shift data with those for the analogous α- and γ- cyclodextrin complexes provides an insight into the factors affecting the stabilities and structures of these complexes.