SUPRAMOLECULAR ADDUCTS OF FERROCENE AND 5 BILE-ACID DERIVED TRIOLIDES

Formation of supramolecular adducts of ferrocene (guest) and cyclic he ad-to-tail trimers (hosts) derived from bile acid: 3 alpha-hydroxy-5 b eta-cholan-24-oic acid triolide (1), 3 alpha-hydroxy-7-oxo-5 beta-chol an-24-oic acid triolide (2), 3 alpha-hydroxy-12-oxo-5 beta-cholan-24-o ic acid triolide (3), 3 alpha-hydroxy-7 alpha-trifluoroacetoxy-6 beta- cholan-24-oic acid triolide (4) and 3 alpha-hydroxy-12 alpha-TFA-5 bet a-cholan-24-oic acid triolide (5) (TFA = trifluoroacetoxy) have been s tudied by H-1 NMR. The best computer-assisted data fitting on the H-1- NMR chemical shift data was given by a 1:2 (guest/host) association mo del. The association constants vary in the range 170-990 M-1, 7-oxo-su bstituted triolide 2 and 12 alpha-TFA triolide 5 showing the largest a nd smallest values respectively. Generally, triolides bearing substitu ents at the position C-7 (2 and 4), when compared with the 12-substitu ted derivatives 3 and 5, seem to favour adduct formation, while a TFA group at the position C-7 or C-12 seems to hinder the adduct formation in comparison with the ore-substituted congeneers. This finding may b e accounted for by the bulky character of the TFA group when compared to the oxo group.