Calixarenes and calix[4]resorcinarenes as chiral NMR solvating agents

Calixarenes (CAs) and calix4]resorcinarenes are cavity compounds, chiral analogues of which have the potential to be used as reagents for the differentiation of enantiomers in NMR spectroscopy. The nature of the substituent groups attached to the cavity permits the preparation of organic- or water-soluble analogues. In NMR applications, chirality of the CAs or calix4]resorcinarene is usually achieved through the attachment of enantiomerically pure substituent groups. The use of inherently chiral analogues for chiral differentiation is less common. The range of CAs and calix4]resorcinarenes that have been used for chiral analysis in NMR spectroscopy is reviewed.