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  • N-linked peptidocalix[4]arene bisureas as enantioselective receptors for amino acid derivatives.

N-linked peptidocalix[4]arene bisureas as enantioselective receptors for amino acid derivatives.

The Journal of organic chemistry (2007-03-28)
Anton V Yakovenko, Vyacheslav I Boyko, Vitaly I Kalchenko, Laura Baldini, Alessandro Casnati, Francesco Sansone, Rocco Ungaro
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-D-phenylalaninate anion with an interesting enantioselectivity (KDass/KLass=4.14), which is explained on the basis of a three-point interaction mode of binding.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
N-Acetyl-L-phenylalanine, ReagentPlus®, 99%