Chiral recognition by resorcin[4]arene receptors: Intrinsic kinetics and dynamics

Molecular recognition of representative amino acids (A) by a chiral amido[4]resorcinarene receptor (1(L)) was investigated in the gas phase by ESI-FT-ICR mass spectrometry. The ligand displacement reaction between noncovalent diastereomeric [1(L)(.)H(.)A](+) complexes and the 2-aminobutane enantiomers (B) exhibits a distinct enantioselectivity with regard to both the leaving amino acid A and the amine reactant B. The emerging selectivity picture, discussed in the light of molecular mechanics and molecular dynamics calculations, points to chiral recognition by 1(L), as determined by the effects of the host asymmetric frame on the structure, stability, and rearrangement dynamics of the diastereomeric [1L.H.A](+) complexes and the orientation of the amine reactant B in encounters with [1(L)(.)H(.)A](+). The results contribute to the development of a dynamic model of chiral recognition of biomolecules by enzyme mimics in the unsolvated state.