Monomeric and dimeric 9-O anthraquinone and phenanthryl derivatives of cinchona alkaloids as chiral solvating agents for the NMR enantiodiscrimination of chiral hemiesters.

ABSTRACT

Mono- and bis-alkaloid chiral auxiliaries with anthraquinone or phenanthryl cores were probed as chiral solvating agents (CSAs) for the enantiodiscrimination of chiral cyclic hemiesters. The dimeric anthraquinone derivative and the monomeric phenanthryl one showed remarkable efficiency in the nuclear magnetic resonance (NMR) differentiation of enantiomeric mixtures of hemiesters. An anthraquinone analogous with a single alkaloid unit was remarkably less effective. The conformational prevalence of the chiral auxiliaries were ascertained by NMR.