Real time band selective F1 -decoupled proton NMR for the demixing of overlay spectra of chiral molecules

Insight into old and new pure shift nuclear magnetic resonance methods for enantiodiscrimination

Enantiodiscrimination and their quantification using nuclear magnetic resonance (NMR) spectroscopy has always been a subject of great interest. Proton is the nucleus of choice for enantiodiscrimination due to its high sensitivity and ubiquitous presence in nature. Despite its advantages, enantiodiscrimination suffers from extensive signal splitting by the proton-proton scalar couplings, which give complex multiplets that spread over a frequency range of some tens of hertz. These multiplets often overlap, further complicating interpretation of the spectra and quantifications. In the present review, we discuss some of the recent developments in the pure shift ¹ H NMR based methods for enantiomer resolution and enantiodiscrimination. We also compare various pure shift methods used for enantiodiscrimination and measurement of enantiomeric excess, considering the fact that conventional ¹ H NMR fails to provide any detailed insight.

Multiple homonuclear band-selective decoupling NMR: Fast and unambiguous determination of diastereomeric excess

Discrimination and quantification of chiral stereoisomers have been studied by different analytical methods, and NMR has emerged as a powerful one with the advancements in pure-shift NMR methods. In the present manuscript, an al-F1F2-MHOBS-DIAG NMR method for the quantification of diastereomeric excess ratio (dr) has been proposed and demonstrated, using hesperidin and naringin mixtures. This method enables simultaneous quantification of dr at multiple resonances, in a single experiment, and it takes only 10 min to record. The present method uses spectral aliasing and thus demands only very few indirect dwell increments. Further, the measured dr values are very reliable, because we consider several spins for the quantification.