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 α -phenylethyl and α -(1-naphthyl)ethyl 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 enantioselectivity (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.

Synthesis and Enantiomeric Recognition Studies of Novel C2-Symmetrical Chiral Tetra-Amide Compounds

“…Since the pioneering research on the application of chiral recognition reported by Cram and coworkers, great number of chiral macrocyclic and complex structured ligands have been synthesized and studied for enantiomeric recognition of racemic compounds (Nakashima et al, 2000;Lu et al, 2010;Lee et al, 2010;Deniz et al, 2011;Park et al, 2012;Sipos et al, 2012;Bako et al, 2012;Howard et al, 2013;Yi et al, 2013;Tsioupi et al, 2013;Paik et al, 2013;Guo et al, 2013;Liu et al, 2014;Şeker et al, 2014) However, in recent years non-cyclic ligands have begun to be used in enantiomeric recognition studies (Peri et al, 1998;Liu et al, 2001;Wang et al, 2007;Ballistreri et al, 2010;Aral et al, 2013;Kormos et al, 2013;Ulatowski and Jurczak, 2014;Pal et al, 2015;Forte et al, 2015;Pal et al, 2016). Still there are limited papers have been reported on the using non-cyclic ligands as chiral receptor for enantiomeric recognition of the racemic compounds.…”