The Complexation of Some Amino Acids by Isomers of Dicyclohexano-18-Crown-6 and 18-Crown-6 in Methanol

The complexation of some amino acids (glycine, L-alanine,L-leucine, L-valine, and L-serine) by the cis-syn-cisand cis-anti-cis isomers of dicyclohexano-18-crown-6 (DC18C6) in methanol was studied by calorimetric titrationmeasurements. Both isomers exhibited a significant ability to bind the amino acidsmentioned above. The results obtained demonstrate that the structural isomers ofDC18C6 are significantly different in terms of thermodynamics concerning their complexationwith the amino acids. The stability constants and the thermodynamic data forthe reaction of the amino acids under study in protonated form and 18-crown-6 (18C6) are reported.