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.