Chiral discrimination controlled by the solvent dielectric constant

Chiroselective molecular recognition accompanied by a change in configuration of a target substrate has been studied. (RS)-alpha-Amino-epsilon-caprolactam 1 was used as the target substrate to be resolved while N-tosyl-(S)-phenylalanine 2 was used as the chiral selector. The dielectric constant (L) of the solvent was found to have a profound effect on the chiroselective molecular recognition. The specific chiral selector (S)-2 not only recognized both enantiomers (R)- and (S)-1 individually to be deposited as the less-soluble salt from the different solvent but also controlled the configuration and diastereomeric excess of the less-soluble diastereomeric salt by simple adjustment of the solvents dielectric constant. The chiroselective recognition mechanism was examined based on the crystal structures of the salts, (S)-1-(S)-2-H2O and (R)-1-(S)-2, obtained from the resolution process. (C) 2004 Elsevier Ltd. All rights reserved.