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Synthesis of Bridged and Metallobridged Bis(β‐cyclodextrin)s Containing Fluorescent Oxamidobisbenzoyl Linkers and Their Selective Binding towards Bile Salts
Author(s) -
Liu Yu,
Yu HongMei,
Chen Yong,
Zhao YanLi
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200501187
Subject(s) - chemistry , circular dichroism , fluorescence , perchlorate , stoichiometry , intramolecular force , cyclodextrin , salt (chemistry) , cholic acid , stereochemistry , fluorescence spectroscopy , medicinal chemistry , crystallography , bile acid , organic chemistry , ion , biochemistry , physics , quantum mechanics
A series of β‐cyclodextrin (β‐CD) dimers containing fluorescent 2,2′‐oxamidobisbenzoyl and 4,4′‐oxamidobisbenzoyl linkers—that is, 6,6′‐[2,2′‐oxamidobis(benzoylamino)]ethyleneamino‐6,6′‐deoxy‐bis(β‐CD) ( 2 ), 6,6′‐[2,2′‐oxamidobis(benzoylamino)]diethylenediamino‐6,6′‐deoxy‐bis(β‐CD) ( 3 ), 6,6′‐[4,4′‐oxamidobis(benzoylamino)]ethyleneamino‐6,6′‐deoxy‐bis(β‐CD) ( 4 ), and 6,6′‐[4,4′‐oxamidobis(benzoylamino)]diethylenediamino‐6,6′‐deoxy‐ bis(β‐CD) ( 5 )—were synthesized from the corresponding oxamidobis(benzoic acid)s through treatment with mono[6‐aminoethyleneamino‐6‐deoxy]‐β‐CD or mono[6‐diethylenetriamino‐6‐deoxy]‐β‐CD. Further treatment of 2 – 5 with copper perchlorate gave their Cu II complexes 6 – 9 in satisfactory yields. The conformation and binding behavior of 2 – 9 towards two bile salt guests—sodium cholate (CA) and sodium deoxycholate (DCA)—was comprehensively investigated by circular dichroism, 2D NMR spectroscopy, and fluorescence spectroscopy in Tris‐HCl buffer solution (pH 7.2) at 25 °C. Thanks to the cooperative host–linker–guest binding mode, the stoichiometric 1:1 complexes formed by bis(β‐CD)s 2 – 5 with bile salts gave high stability constants ( K S values) of up to 10 3 –10 4 M −1 . Significantly, benefiting from the intramolecular 1:2 or 2:4 binding stoichiometry, the resulting complexes of metallobis(β‐CD)s 6 – 9 with bile salts gave much higher K S values of up to 10 6 –10 7 M −2 . The enhanced binding abilities of bis(β‐CD)s and metallobridged bis(β‐CD)s are discussed from the viewpoints of induced‐fit interactions and multiple recognition between host and guest.