CDs in NMR spectroscopy

In NMR spectroscopic analysis, CDs are mainly used as chiral NMR shift reagents. The complexation with CDs can affect the character of the NMR spectra of 

NMR spectroscopy prove the formation of an inclusion complex. When the guest molecule is enclosed in the CD cavity, the resonance signals of protons located inside the cavity (3H and 5H) are shifted in the spectrum. The signals of protons located on the outer side of the cavity (2H, 4H, 6H) remain relatively unaffected. 

Up to now, NMR spectroscopy has become the most powerful approach for the study of inclusion complex formation between CDs and a variety of guest molecules, from initial H NMR in solution to C NMR, N NMR, NMR and 

A NMR study on the formation of diastereoisomeric inclusion complexes between fluorinated amino acid derivatives and a-CD in 10% D2O solution shows that the chemical shifts of the D-amino acid derivatives included by a-CD are upheld from those of their L analogues [77]. The shift difference between the diastereoisomers formed with D and L enantiomers can be used for chiral analysis and optical purity determinations. For example, the interaction of -CD with propanolol hydrochloride produces diastereomeric pairs. The protons of the antipode give NMR signals which differ in chemical shifts in D2O solution at 400 MHz. The intensity of the resonance signals for each diastereoisomer has been used for optical purity determination. By adding racemate to pure (—) isomer, this technique is able to measure optical purity of propanolol hydrochloride in water down to the level of 1%. 

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