Enantiomeric purity determination by NMR: proving the purity of a single enantiomer

The NMR spectra of separate samples of an analyte complexed with each enantiomer of a chiral solvating agent (CSA) give an accurate estimate of the chemical shifts of racemic analytes in the presence of a single enantiomer of the CSA. This effect allows a CSA-based chiral NMR method to be developed when only a single enantiomer of analyte is available. The ability to develop a method capable of discriminating between enantiomers in these circumstances is useful, for example, to resolve the question of whether racemization has occurred during the synthesis of a chiral molecule.

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tert-Butyl [(1R,2S)-1-(2-cyclopropylpyrimidin-5-yl)-1-hydroxypropan-2-yl]carbamateC15H23N3O3ee >99%[α]D20=-28.5 (c 1.0, CH3CN)Source of chirality: (R)-2-(tert-butoxycarbonylamino)propanoic acidAbsolute configuration: (1R,2S)

3-[(1S)-1-Aminoethyl]-8-chloro-2-phenylisoquinolin-1(2H)-oneC17H15ClN2Oee = 89%[α]D20=-12.0 (c 1.0, CH3CN)Source of chirality: (S)-2-(tert-butoxycarbonylamino)propanoic acidAbsolute configuration: (S)