CONFORMATIONAL ENANTIOMERISM OF BILIRUBIN AND PAMOIC ACID-INDUCED BY PROTONATED AMINOCYCLODEXTRINS

The conformational enantiomerism of (4z,15Z)-bilirubin IX alpha (1) in duced by protonated heptakis(6-amino-6-deoxy)-beta-cyclodextrin (amino -beta-CDx) has been studied in aqueous media by means of CD spectrosco py. A bisignate CD Cotton effect suggests that the dianion of 1 associ ated with protonated amino-beta-CDx : selectively takes a conformation with (P)-helicity. The results clearly indicate that the electrostati c binding between the CO2- groups of 1 and the NK3+ groups of amino-be ta-CDx and the simultaneous inclusion of a dipyrrinone moiety of 1 int o the chiral CDx cavity are essential for the conformational enantiome rism of 1. This has also been applied to the amino-gamma-CDx-induced c onformational enantiomerism of pamoic acid.