NMR Studies of Chiral Discrimination Relevant to the Liquid Chromatographic Enantioseparation by a Cellulose Phenylcarbamate Derivative

Chromatographic enantioseparation of 1,1‘-bi-2-naphthol ( 2 ) and its mono- and di- O -methylated derivatives ( 3a, 3b ), 2,2‘-dihydroxy-6,6‘-dimethylbiphenyl ( 4 ), and 10,10‘-dihydroxy-9,9‘-biphenanthryl ( 5 ) has been performed on cellulose tris(5-fluoro-2-methylphenylcarbamate) ( 1 ) as a chiral stationary phase for high-performance liquid chromatography (HPLC). The complete base-line separation of 2 and 4 was achieved with the elution order of enantiomers such that the ( R )-isomers eluted first followed by the ( S )-isomers. The resolution of 5 and the O -methylated 3 was difficult on 1 . The cellulose derivative 1 dissolved in chloroform also exhibited a chiral discrimination for 2 and 4 in 1 H and 13 C NMR spectroscopies as well as in HPLC. The hydroxy and some aromatic protons and carbon resonances of 2 and 4 were clearly separated into a pair of peaks due to enantiomers in the presence of 1 . The binding geometry and dynamics between 1 and the enantiomers of 2 were investigated on the basis of spin−lattice relaxation time, 1 H NMR titrations, and intermolecular NOEs in the presence of 1 . These NMR data are fully consistent with the chromatographic elution order. These results, combined with molecular modeling, reveal the chiral discrimination rationale.