Six 2,2'-biimidazoles with various amide groups at the 4- and 4'-positions were prepared from 5-propyl-1H-imidazole-4-carboxylic acid ethyl ester. In the final step of the synthesis, biimidazole C2-C2' bond formation was accomplished in 33-45% yield by palladium(0)-catalyzed homocoupling of the corresponding 2-iodoimidazoles. Four of the biimidazoles were studied by X-ray diffraction. In the solid state, all display coplanar imidazole rings, an anti relationship of amide groups, and intramolecular (NHamide...N-imid) and intermolecular (NHimid...O-amide) hydrogen bonding. In CH2Cl2, the emission intensity of the biimidazoles is quenched by the presence of dihydrogenphosphate and chloride anions, but no shifts in lambda(emiss) are observed. Binding constants for 1:1 biimidazole-anion complexation (K-assoc) are on the order of 10(4) M-1 for H2PO4- and Cl-. One of the receptors (bearing 3,5-difluorobenzylamides) is selective for chloride. The participation of the amide NH atoms in anion binding was established by H-1 NMR.
Biimidazole diamide compounds that are useful for binding anions such as sulfate are described, along with the use thereof for purposes such as extracting anions from a waste stream and/or detecting anions.
Participation of host ‘spacer’ atoms in carboxylic acid binding: implications for amino acid recognition
作者:Daniel K. Barnhill、Andrew L. Sargent、William E. Allen
DOI:10.1016/j.tet.2005.06.096
日期:2005.8
Chiral 4,4'-diamidao-2,2'-biimidazoles were synthesized and found to bind N-Boc protected amino acids in CDCl3. The biinmidazole that features (R)-tetrahydrofurfuryl units discriminates between N-Boc-L-Ser (K-assoc 120 M-1) and its non-natural D-enantiomer (270 M-1). X-ray diffraction and computational analyses show that members of this receptor class adopt a cleft-like conformation, presenting a donor-spacer-donor-acceptor H-bonding array. Complexes of such biimidazoles with the COOH unit of amino acids are stabilized by direct involvement of what is nominally a 'spacer' atom. unlike other D-Sp-D-A hosts, (c) 2005 Elsevier Ltd. All rights reserved.
US7078528B2
申请人:——
公开号:US7078528B2
公开(公告)日:2006-07-18
Anion Binding by Fluorescent Biimidazole Diamides
作者:Corey P. Causey、William E. Allen
DOI:10.1021/jo020098v
日期:2002.8.1
Six 2,2'-biimidazoles with various amide groups at the 4- and 4'-positions were prepared from 5-propyl-1H-imidazole-4-carboxylic acid ethyl ester. In the final step of the synthesis, biimidazole C2-C2' bond formation was accomplished in 33-45% yield by palladium(0)-catalyzed homocoupling of the corresponding 2-iodoimidazoles. Four of the biimidazoles were studied by X-ray diffraction. In the solid state, all display coplanar imidazole rings, an anti relationship of amide groups, and intramolecular (NHamide...N-imid) and intermolecular (NHimid...O-amide) hydrogen bonding. In CH2Cl2, the emission intensity of the biimidazoles is quenched by the presence of dihydrogenphosphate and chloride anions, but no shifts in lambda(emiss) are observed. Binding constants for 1:1 biimidazole-anion complexation (K-assoc) are on the order of 10(4) M-1 for H2PO4- and Cl-. One of the receptors (bearing 3,5-difluorobenzylamides) is selective for chloride. The participation of the amide NH atoms in anion binding was established by H-1 NMR.