title: NMR-aided differentiation of enantiomers: Signal enantioresolution.
abstract: NMR-aided enantiodiscrimination using chiral auxiliaries (CAs) is a recognized method for differentiating enantiomers and for measuring enantiomeric ratios (er). Up to the present, the study, optimization, and comparison of such methods have been performed based on the enantiodifferentiation of NMR signals via analyzing non-equivalent chemical-shift values (ΔΔδ) of the diastereoisomeric species formed. However, a poor and non-reliable comparison of results is often obtained via the analysis of ΔΔδ exclusively. In here, the concept of enantioresolution of an individual NMR signal and its importance for NMR-aided enantiodifferentiation studies is introduced and discussed. In addition, the enantioresolution quotient, E, is proposed as the parameter to describe its quantification. Complementary to measuring ΔΔδ, the experimental determination of E allows a more reliable interpretation of the results and opens up new possibilities for the study of enantiodifferentiation data derived from novel NMR experiments, setup improvements or new CAs. Finally, the different relationships between signal enantiodifferentiation, signal enantioresolution, and other main experimental issues of enantiodifferentiation experiments are addressed.
authors.affiliation: Servei de Ressonància Magnètica Nuclear and Departament de Química, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain.
authors.forename: Míriam
authors.initials: M
authors.lastname: Pérez-Trujillo
authors.affiliation: Servei de Ressonància Magnètica Nuclear and Departament de Química, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain.
authors.forename: Teodor
authors.initials: T
authors.lastname: Parella
authors.affiliation: European Neuroscience Institute Göttingen (ENI-G) & DFG Research Center Molecular Physiology of the Brain (CMPB)/EXC 171 "Microscopy at the Nanometer Range", Grisebachstrasse 5, 37077 Göttingen, Germany. Electronic address: lars.kuhn@gwdg.de.
authors.forename: Lars T
authors.initials: LT
authors.lastname: Kuhn
mesh_terms: D000465:Algorithms; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D013237:Stereoisomerism
keywords: Chiral complexing agents; Enantiodifferentiation; Enantioresolution; Enantioresolution quotient; NMR spectroscopy