C2-Symmetric chiral diamine ligands for enantiomeric recognition of amino acid esters and mandelic acid by proton NMR titration method

Abstract

Two novel C 2 -symmetric chiral diamines containing -phenylethyl and -(1-naphthyl)eth yl chiral subunits were prepared with quantitative yields. Enantiomeric recognition properties of these simple structured diamine ligands towards D- and L-amino acid esters and D- and L-mandelic acid were examined by the 1 H NMR titration method. These ligands exhibited strong complexation (with K f up to 2481 M 1 ) and good enantioselectivi (up to K L /K D = 4.08) towards the mandelic acid enantiomers. The results show that simple structured and easily accessible acyclic C 2 -symmetrical compounds can also be used for enantiomeric recognition of racemic amino acids and mandelic acid in addition to complex molecules such as crown ethers and other cyclic molecules.