A Macrobicyclic Polyphenoxide as Receptor Analogue for Choline and Related Ammonium Compounds

Abstract

ing that the 'JC.H coupling constants for the inner atoms (C3, C4) are larger than those for the terminal atoms (C2, C5, and C6)."] In analogy to the known CpCo(q4-1,3diene) compounds, we assume that each diene unit is pla-narlX1 but that the two outer diene units are slightly bent with respect to the inner diene."] The electron delocalization in 4 is essentially suppressed, which means that biphenyl in 4 is best described by a Kekule structure. Although there are numerous examples of the reduction or suppression of the aromaticity of benzene, naphthalene, or anthracene by q2-, q3-, or q4complexation to a suitable metal complex compound 4 is, to the best of our knowledge, the first example for the transformation of an aromatic system with 12 x-electrons into a system of three q4-bonded dienes. Experimental ProcedureA solution of 5 (4.9 g, 10.7 mmol) and 6 (1.8 g, 21.4 mmol) in 80 mL of ether was prepared at -80°C and then allowed to warm over several hours to 20°C. After 24 h, the ether was removed under vacuum and the residue was extracted with pentane. After filtration to remove the LiCI, the solvent was removed from the filtrate under vacuum. The remaining LiCl was removed by extraction with pentane, filtration, and removal of the pentane from the filtrate. This procedure was carried out three times. Finally, the residue was dried at 20"C/IO-4 torr to remove the biphenyl. The residue was dissolved in 2 0 0 m L of pentane and filtered, and the filtrate was concentrated to 40 mL. Upon standing at -S O T , the concentrated solution slowly afforded 4 (3.6 g, 4.9 mmol, 69%) as black crystals. Correct elemental analysis and mass spectrum. Comparison of the "C-NMR data of 4 with those of the s-cis/trans isomers of [Cp2Zr(q4-butadiene)] also indicates that the inner diene unit has the s-cis configuration; see also G. Erker,

Complexation of basic amino acids by water-soluble calixarene sulphonates as a study of the possiblemechanisms of recognition of calixarene sulphonates by proteins

“…3 Their ease of production and relative simplicity of chemical modification have produced increased interest in their chemistry over the last few years. A resorcinol-derived calix-arene has been shown by Schneider et al 4 to form complexes with organic ammonium ions. In addition, the electrostatic binding of quaternary amines to water-soluble calixarene sulphonate derivatives has been investigated by Morozumi and Shinkai; 5 in particular, the inclusion complex formed from p-sulphonated calix [4]arene and trimethylanilinium was studied by 1 H and 13 C NMR spectroscopy.…”

“…A resorcinol-derived calix-arene has been shown by Schneider et al 4 to form complexes with organic ammonium ions. In addition, the electrostatic binding of quaternary amines to water-soluble calixarene sulphonate derivatives has been investigated by Morozumi and Shinkai; 5 in particular, the inclusion complex formed from p-sulphonated calix [4]arene and trimethylanilinium was studied by 1 H and 13 C NMR spectroscopy. 6 However, in spite of extensive early work of the biological properties of the p-sulphonated calixarenes, 7 it is only very recently that interest in their biomedical potential has come to the fore again.…”

“…Strong electrostatic binding occurs for calix [4]arene sulphonate with both lysine and arginine at pH 1 and 5. For the higher calixarenes, only weak interactions at the faces of the flattened macrocycles occur.…”

Encapsulation of tetramethylphosphonium cations

“…Ammonium cations have proven to be good guest candidates for resorcinarene complexation since they have the possibility to interact via cation … π and C-H … π interactions as well as advantageously fill the empty space in the hollow cavity of the resorcinarene host [5]. Under neutral conditions, closer to the biological environment, the binding of quaternary alkyl ammonium cations is significantly weakened compared to complexation in alkaline solvents [10]. Mass spectrometry [11] is an important tool to examine binding interactions of cations in the gas phase.…”

The functional architecture of the acetylcholine nicotinic receptor explored by affinity labelling and site-directed mutagenesis

“…This aromatic basket model is consistent with the observation that binding of methyl-substituted ammonium groups by macrocyclic compounds requires not only electrostatic but also hydrophobic interactions (Dhaenens et al 1984). Both these interactions can be provided by strictly aromatic macrocycles (Schneider et al 1986(Schneider et al , 1988Sheppod et al 1986) and the presence of aromatic side chains in the binding sites for quaternary ammonium ligands appears to be a general property shared by several acetylcholine binding proteins, such as antiphosphorylcholine antibodies (Satow et al 1986), acetylcholinesterase (Sussman et al 1991), muscarinic acetylcholine receptors (Hibert & Trumpp-Kallmeyer, 1991;Wess et al 1991) and also in potassium channel mutants which bind tetraethyl ammonium (Heginbotham & McKinnon, 1992).…”