Configurational assignment of vic-amino alcohols from their circular dichroism spectra with dirhodium tetraacetate as an auxiliary chromophore

Abstract

The in situ formed complexes of dirhodium(II) tetraacetate with optically active derivatives of the 1,2-amino alcohols ephedrine and adrenaline show circular dichroism spectra suitable for determination of their absolute configuration. According to the M- or P-helicity of the N–C–C–O moiety the investigated compounds generate negative or positive Cotton effects at around 300 and 440 nm, respectively. The third prominent CE of an opposite sign to the first two occurs at ca. 380 nm. It is demonstrated that the in situ method allows fast and easy configurational assignment based on the helicity rule that connects the signs of the Cotton effects at around 300 and 440 nm with the sign of the N–C–C–O torsional angle.