Chiral Analysis by NMR Spectroscopy: Chiral Solvating Agents

An electronic circular dichroism spectroscopy method for the quantification of L- and D-amino acids in enantiomeric mixtures

“…The application of MS in chiral analysis is based on mass-resolve adducts generated by the additives and the analytes [14][15][16][17]. Chiral reagents are used for chiral analysis of NMR [18,19].…”

Hydrolysis and Enantiodiscrimination of (R)- and (S)-Oxazepam Hemisuccinate by Methylated β-Cyclodextrins: An NMR Investigation

“…As a matter of fact, interaction at the apolar cavity of cyclodextrins constitutes a privileged interaction mechanism with several kinds of substrates leading to the inclusion of their apolar moieties [14][15][16][17][18]. Moreover, being cyclodextrins chiral, the formation of diastereomeric inclusion complexes produces potentially differentiable signals for the two included enantiomers by chromatographic [19][20][21][22][23][24][25] and/or spectroscopic techniques [24][25][26][27][28]. Commonly, inclusion does not involve polar pendants of enantiomeric substrates which may protrude from the large and small rims of the cyclodextrins and interact with cyclodextrin hydroxyl functions incurring into hydrolytic processes, which have been reported for ester compounds [29][30][31].…”

“…Both aspects were investigated by nuclear magnetic resonance (NMR) spectroscopy. As a matter of fact, CDs are very popular chiral solvating agents (CSAs) for NMR, which have been employed to differentiate NMR signals of several classes of enantiomeric substrates [26][27][28]. Furthermore, quantitative response of NMR makes this technique very appealing both for the determination of enantiomeric excesses and for the detection and quantification of degradation products.…”

Chiral mono- and dicarbamates derived from ethyl (S)-lactate: convenient chiral solvating agents for the direct and efficient enantiodiscrimination of amino acid derivatives by 1H NMR spectroscopy

“…[7][8][9][10] The development of validated procedures of quantication of enantiomers requires suitable analytical or preparative methods of separation: several approaches are available, chromatographic and spectroscopic mainly. [11][12][13][14][15][16] Among spectroscopic methods, nuclear magnetic resonance (NMR) spectroscopy 15,16 has been playing a leading role since the 60s/ 70s, when the possibility to detect different NMR signals of enantiomers, transferred into a diastereomeric environment by use of suitable chiral auxiliaries, had been suggested. Under the impulse of these earliest experiments, three main classes of chiral auxiliaries for NMR spectroscopy were proposed, i.e.…”

“…Proposed chiral solvating agents span from very simple low molecular weight compounds, to natural products or systems with highly preorganized structures able to enhance the enantioselectivity of the interaction with the chiral substrates. 15,16 However, in the everyday practice of NMR detection and quan-tication of enantiomers, mainly for trial separations, chiral auxiliaries coming from commercially available inexpensive products should be privileged. With this idea in mind, we took into consideration ethyl lactate, a very cheap product, as an attractive building block for the development of new CSAs for NMR spectroscopy, obtained by simple derivatization procedures of its functional groups.…”