CHROMATOGRAPHIC ENANTIOMER SEPARATION, CIRCULAR-DICHROISM SPECTRUM, AND ABSOLUTE-CONFIGURATION OF THE 7-METHOXYCOUMARIN SYN HEAD-TO-TAIL DIMER

The 7-methoxycoumarin syn, head-to-tail dimer with C2 symmetry has been resolved into enantiomers by repeated column chromatography on a chiral stationary phase (CSP) consisting of poly[ethyl (S)-2(acryloylamino)-3-phenylpropionate] immobilized in the pores of macroporous poly(trimethylolpropyl trismethacrylate), TRIM, with hexane-dioxane (1:1, v/v) as the mobile phase. The CD spectra of the pure enantiomers have been recorded, and a theoretical CD spectrum has been calculated based on the geometry from a published X-ray crystallographic study and on transition moments and transition charge densities from the UV spectrum and from CNDO/S calculations. Good agreement between the calculated CD spectrum and that of one of the enantiomers permits the assignment of the absolute configuration of the latter.