title: An extraction-based assay for neutral anionophores: the measurement of high binding constants to steroidal receptors in a nonpolar solvent.
abstract: The extraction-based protocol for measuring binding constants, developed by Cram and co-workers, has been extended for use with anionic substrates. The method is especially useful for high-affinity receptors, allowing very high binding constants to be measured in nonpolar solvents. Distribution constants K(d) between chloroform and water have been obtained for tetraethylammonium chloride and bromide, thus calibrating the method for these two substrates. Application to steroidal podands 5-9 has confirmed the ability of electron-withdrawing groups to enhance hydrogen-bond donor capabilities. Binding constants of approximately 3 x 10(7) M(-1) have been measured for the most powerful receptor 7. An X-ray crystal structure of 15, the methyl ester analogue of 7, reveals a well-defined binding site preorganised for anion recognition.
authors: School of Chemistry, University of Bristol Cantock's Close, Bristol, UK.
authors: Alan J
authors: AJ
authors: Ayling
authors: Shay
authors: S
authors: Broderick
authors: John P
authors: JP
authors: Clare
authors: Anthony P
authors: AP
authors: Davis
authors: M Nieves
authors: MN
authors: Pérez-Payán
authors: Maarit
authors: M
authors: Lahtinen
authors: Maija J
authors: MJ
authors: Nissinen
authors: Kari
authors: K
authors: Rissanen
mesh_terms: D000838:Anions / Q000737:chemistry*; D001665:Binding Sites; D006860:Hydrogen Bonding; D007476:Ionophores / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D012997:Solvents; D013256:Steroids / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000838:Anions; D007476:Ionophores; D012997:Solvents; D013256:Steroids