Bisurea calix[4]arenes 1 and 2 possessing l-amino acid moieties at the lower rim were synthesized by reaction of the methyl esters of glycine, l-alanine, or l-isoleucine with the appropriate isocyanate (12 or 13), obtained with a safe and efficient Curtius rearrangement from the corresponding carboxylic acid derivatives. The conformational properties of the ligands 1 and 2 were investigated by means of a combined NMR and molecular modeling study which evidences that they are deeply influenced by strong intramolecular H-bonds between the urea NH groups and the vicinal phenolic oxygen atoms or the opposite urea C O group. Complexation studies performed by ESI-MS and NMR spectroscopy in acetone solution show that the binding ability of these bisurea hosts decreases by increasing the side chain size of the amino acid. Host 2b has a remarkable binding ability for the N-acetyl-dphenylalaninate anion with an interesting enantioselectivity ( / = 4.14), which is explained on the basis of a three-point interaction mode of binding.
N-Linked Peptidocalix[4]arene Bis-Ureas as Enantioselective Receptors for Amino Acid Derivatives / A. V., Yakovenko; V. I., Boyko; V. I., Kalchenko; Baldini, Laura; Casnati, Alessandro; Sansone, Francesco; Ungaro, Rocco. - In: JOURNAL OF ORGANIC CHEMISTRY. - ISSN 0022-3263. - 72:(2007), pp. 3223-3231. [10.1021/jo062410x]
N-Linked Peptidocalix[4]arene Bis-Ureas as Enantioselective Receptors for Amino Acid Derivatives
BALDINI, Laura;CASNATI, Alessandro;SANSONE, Francesco;UNGARO, Rocco
2007-01-01
Abstract
Bisurea calix[4]arenes 1 and 2 possessing l-amino acid moieties at the lower rim were synthesized by reaction of the methyl esters of glycine, l-alanine, or l-isoleucine with the appropriate isocyanate (12 or 13), obtained with a safe and efficient Curtius rearrangement from the corresponding carboxylic acid derivatives. The conformational properties of the ligands 1 and 2 were investigated by means of a combined NMR and molecular modeling study which evidences that they are deeply influenced by strong intramolecular H-bonds between the urea NH groups and the vicinal phenolic oxygen atoms or the opposite urea C O group. Complexation studies performed by ESI-MS and NMR spectroscopy in acetone solution show that the binding ability of these bisurea hosts decreases by increasing the side chain size of the amino acid. Host 2b has a remarkable binding ability for the N-acetyl-dphenylalaninate anion with an interesting enantioselectivity ( / = 4.14), which is explained on the basis of a three-point interaction mode of binding.File | Dimensione | Formato | |
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