CHIRAL RECOGNITION IN AQUEOUS-SOLUTIONS BETWEEN ENANTIOMERIC ALPHA-AMINO-ACIDS BEARING SUBSTITUTED ALKYL CHAINS AT 25-DEGREES-C - THE PREFERENTIAL CONFIGURATION MODEL

Calorimetric, densimetric, and nuclear relaxation time measurements we re carried out at 25 degrees C on binary and ternary aqueous solutions containing L and D forms of the following amino acids bearing substit uted alkyl chains: lysine, glutamine, arginine, asparagine, serine, an d homoserine. For three of them (lysine, glutamine, and arginine), ver y high differences were found between the values of the homochiral and heterochiral pairwise enthalpic interaction coefficients. Volume and spectroscopic data shaved that it is possible to detect chiral recogni tion by techniques other than calorimetric. The role of the zwitterion ic interaction and of the substituted side chain is discussed to expla in the enhanced chiral recognition of these alpha-aminoacids in respec t to those bearing unsubstituted alkyl chains (alanine, alpha-aminobut yric acid, valines and leucines).