From Chiral Drugs to Chiral Metabolites: The NMR Approach

Quantification and identification of chiral drugs and their metabolites constitutes a significant issue for both the pharmaceutical industry and the regulatory authorities, which led to a continuous growth of research areas devoted to the development of direct methods of discrimination of enantiomers. Stereoisomers frequently differ in terms of their biological activity and pharmacokinetic profiles as well as their metabolites can be toxic or pharmacologically active, just like drug candidates. NMR spectroscopy provides several tools in the field of the identification and quantification of chiral compounds, based on the use of suitable chiral auxiliaries which have the role of converting enantiomeric mixtures into their diastereoisomeric derivatives or solvates, the NMR resonances of which are distinguishable in principle. The survey will be addressed on the NMR determinations of the enantiomeric purity of chiral compounds, with an outline of the three classes of chiral auxiliaries for NMR, without any intent of giving an exhaustive analysis of literature data. Particular attention will be focused on the literature regarding the use of NMR spectroscopy for the identification and quantification of chiral drugs and metabolites.