Optimization of enantiomeric separation for quantitative determination of the chiral drug propranolol by 1H-NMR spectroscopy utilizing a chiral solvating agent

High-field H-1-NMR methodology for enantiomeric composition determination of the chiral drug propranolol utilizing a chiral solvating agent is reported, Optimal experimental conditions for the resolution of enantiomers were determined by studying the interaction of substrate concentration, chiral solvating agent concentration and temperature. The success of the method is based on the selection of a chiral solvating agent that has the following two characteristics. First, it possesses functional groups that are complimentary to those of the chiral substrate for significant interaction to occur. Second, it has a group of diamagnetic anisotropy near its stereogenic center for translating spatial environments of solute nuclei into different magnetic environments that are measurable by NMR spectroscopy. Optical purities were determined on the basis of the intensities of the methyl proton resonances. The analysis of synthetic enantiomeric mixtures of propranolol by the proposed NMR method resulted in assay values, which agreed closely with the known quantities of each enantiomer in the mixtures tested. The mean +/- SD recovery values for the (R)-(+)-enantiomer was 100.0 +/- 0.6% of added antipode (n = 7). (C) 2000 Elsevier Science B.V. All rights reserved.