Determination of enantiodiscrimination of chiral acids and tetrahydropyrimidine derivatives by bis-thiourea derived chiral solvating agents by NMR spectroscopy

Abstract

Synthesis of four derivatives of chiral bis-thiourea have been prepared from (S)-(1- isocyanatoethyl)benzene and diamines. The bis-thiourea derivatives were scanned as Chiral Solvating Agents (CSA) for detecting discrimination of optically pure acids by 1H NMR spectroscopy. Addition of amine during NMR experiments was found essential to effect deprotonation of carboxylic acid substrates. The present CSA were found to show effective chiral discrimination of neutral analytes such as tetrahydropyrimidine derivatives. Further they showed good molecular recognition in case of 1,4-dihydropyridine carboxylic acid, an intermediate of cardiovascular drug Benidipine-HCl and ibuprofen.