INDUCED CIRCULAR-DICHROISM AND CHIRAL DISCRIMINATION OF RACEMATES REVISITED - BILIRUBINS AS ILLUSTRATIVE EXAMPLES

The scope and limitation of the circular dichroism of racemates induce d by an optically active cosolute (ICD) are elaborated. Accordingly, t he interpretation of ICD spectra depends upon the barrier to interconv ersion of enantiomers, the degree of complexation the availability of reference values and population and spectral differences of the specie s involved. The distinct nature of these factors may occasionally prev ent a meaningful application of this technique in the field of molecul ar and chiral recognition. The relevance of the more general considera tions Is outlined and eventual implications for the ICD spectra of bil irubin-IX alpha (1) reported in the literature are provided by the bri dged analogues 2, 3a and 3b.