Inclusion compounds in water: Thermodynamics of the interaction of cyclomaltohexaose with amino acids at 25°

Abstract

The interaction in water of some α-amino acids (alanine, 2-aminobutyric acid, valine, norvaline, leucine, isoleucine, norleucine, methionine), N-acetyl-l-valinamide, and N-acetyl-l-leucinamide with cyclomaltohexaose (α-cyclodextrin) has been studied by calorimetry at 25°. The results indicate that inclusion occurs only with those amino acids bearing longer alkyl chains, the complexes formed are weak, and α-cyclodextrin does not discriminate between the d and l forms of the amino acids. The association constants are smaller than those for alcohols having comparable side-chains; hence, the presence of the zwitterion inhibits the inclusion process. © 1989