title: Biomimetic macrocyclic receptors for carboxylate anion recognition based on C-linked peptidocalix[4]arenes.
abstract: Two neutral macrobicyclic anion receptors 4 and 6, containing a calix[4]arene in the cone conformation, two l-alanine units, and a 2,6-diacylpyridine or a phthaloyl bridge, are described. The x-ray crystal structure of the acetone complexes of the pyridine containing macrocycle 6 shows the four amide NH groups to be in close proximity to the chiral pocket delimited by the pyridine and one aromatic nucleus of the calix[4]arene. This conformation is also the most stable in acetone-d6 solution, as proven by one- and two-dimensional NMR spectral measurements. Electrospray ionization-MS and (1)H NMR experiments reveal that the two ligands strongly bind carboxylate anions in acetone solution. H-bonding interactions between the carboxylate anions and the amide NH groups, together with pi/pi stacking, are invoked to explain the efficiency and the selectivity of these anion receptors.
authors.affiliation: Dipartimento di Chimica Organica ed Industriale dell'Università, Parco Area delle Scienze, 17/A, I-43100 Parma, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sansone
authors.forename: Laura
authors.initials: L
authors.lastname: Baldini
authors.forename: Alessandro
authors.initials: A
authors.lastname: Casnati
authors.forename: Marcio
authors.initials: M
authors.lastname: Lazzarotto
authors.forename: Franco
authors.initials: F
authors.lastname: Ugozzoli
authors.forename: Rocco
authors.initials: R
authors.lastname: Ungaro
mesh_terms: D000838:Anions; D047250:Calixarenes; D002244:Carbon / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry; D019800:Phenol / Q000737:chemistry; D011487:Protein Conformation
chemical_list: D000838:Anions; D008024:Ligands; D046911:Macromolecular Substances; D010455:Peptides; D047250:Calixarenes; D019800:Phenol; D002244:Carbon