• chiral analysis
• Chiral solvating agents
• enantiomeric purity
• NMR spectroscopy
• Thiourea derivatives

Thiourea chiral solvating agents (CSA) for the NMR enantiodiscrimination of chiral substrates have been obtained by reacting chiral amines with isothiocyanates. N-3,5-dinitrobenzoyl (N-DNB), N-trifluoroacetyl (N-TFA) and N-acetyl (N-Ac) derivatives of amino acids with free carboxyl functions have been analyzed, with the co-presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) as third achiral additive, needed for substrate solubilization. C2-symmetrical bis-thiourea CSA derived from (1R,2R)-1,2-bis(2-hydroxyphenyl)ethylenediamine and 3,5-bis(trifluoromethyl)phenylisothiocyanate showed remarkable efficiency in enantiomer differentiation in virtue of the presence of acidic phenolic hydroxyls. Chiral discrimination mechanism has been investigated by means of Diffusion-Ordered Spectroscopy (DOSY) and Rotating frame Overhauser Effect SpectroscopY (ROESY) NMR experiments.