Biomimetic macrocyclic receptors for carboxylate anion recognition based on C-linked peptidocalix[4]arenes.
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.
Sansone
Francesco
F
Dipartimento di Chimica Organica ed Industriale dell'Università, Parco Area delle Scienze, 17/A, I-43100 Parma, Italy.
Baldini
Laura
L
Casnati
Alessandro
A
Lazzarotto
Marcio
M
Ugozzoli
Franco
F
Ungaro
Rocco
R
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
D000838:Anions; D008024:Ligands; D046911:Macromolecular Substances; D010455:Peptides; D047250:Calixarenes; D019800:Phenol; D002244:Carbon