Chiroptical sensing of amino acids by stereodynamic imprinting into the Zn-II-Complex generating a dihedral chirality

Abstract

A stereodynamic chiroptical sensor based on three-component assembly of 3-(di-2-picolylaminoacetamido)-2-formyl-naphthalene (1), Zn-II and amino acids was developed. The imine formed between 1 and an amino acid has six coordination sites to bind tightly ZIP ion. The crystal structure of the Zn-II complex, 1-Zn-D-Phe, revealed that the naphthyl ring is tilted to one pyridine ring to generate axial chirality. The dihedral conformations observed in 1-Zn-D-Phe were herein arbitrarily designated as alpha(1) and alpha(2). DFT calculation suggests that the D-Phe binding prefer the alpha(1)-conformer: the energy of D-Phe-alpha(1) is more stable than L-Phe-alpha(1) by 5.5 kcal/mol. This preference to one diastereomer generates amplification of CD signal with Cotton effect, which can be applied to the determination of ee values of the amino acid.