Sixteen diastereomeric 2,3-dihydrobilatrienes-abc substituted in position 3 with various chiral ligands, seven chiral derivatives of a 2,3-dihydrobilatriene-abc-12-propionic acid and a chiral derivative of a 8,12-bilatriene-abc-dipropionic acid were prepared. The chiroptical properties (CD) of these compounds were used as a monitor for the conformational influence of the various ligands. Therefrom it could be deduced that steric effects play a minor role in determining the topology of the chromophore. On the contrary, dipole-dipole interactions of the various partial moments of bile pigments and of the attached ligands crucially influence the conformational situation of the chromophore. This fact may be significant for the stabilization of certain chromophore conformations in biliproteids.
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