NMR enantiodiscrimination of polar and apolar substrates by multifunctional cyclodextrins

Mixed methylated/carbamoylated cyclodextrins constitute a new class of chiral complexing agents for NMR spectroscopy, which are able to induce anisochrony of enantiomeric mixtures of apolar trisubstituted allenes and polar derivatized compounds most of which are endowed with a π-acidic 3,5- dinitrophenyl ring. The differing contribution to enantiorecognition phenomena of the nature and location of the functional groups on the two cyclodextrin rims was shown. Some interesting aspects of the complexation phenomena, which are the basis of chiral recognition, have been underlined by NMR spectroscopic investigations.