Chiral Recognition of Anions by Fluorescence Tetraamide-Based Receptors Bearing Hydroxy Groups from l-Serine and l-Threonine Residues

Abstract

Chiral recognition abilities of tetraamide-based receptors 1 and 2 bearing l-serine and l-threonine as recognition sites, respectively, and terminal pyrenyl groups as signaling units for enantiomers of biologically important N-acetyl amino acid tetrabutylammonium salts were studied in acetonitrile. The receptors showed ratiometric fluorescence changes upon the addition of chiral guest anions. The binding constants for amino acid derivatives were in the 104–105 mol−1 dm3 range. The chiral discrimination abilities (K11,D/K11,L) of 1 and 2 were significantly large, for instance K11,D/K11,L for Ac-Leu-O− were found to be 3.9 and 4.6, respectively. The complex structures were evaluated by 1H NMR titrations and DFT calculations implying that the effective hydrogen bond formations by six N-H and O-H groups and a CH-π interaction of the acetyl group of d-enantiomer with a terminal pyrenyl group of the receptor.

Advances in fluorescent and colorimetric sensors for anionic species

“…This colour change faded over time but the absorbance peak maximum at 340 nm was not fully restored, indicating the photoreaction was irreversible. Elsewhere, researchers have developed a turn-off excimer emission receptor for chiral amino acids [97].…”

Review of advanced sensor devices employing nanoarchitectonics concepts

“…The discrimination and sensing of chiral substances are regarded as a more difficult task because chiral molecules have identical properties except for their optical activity. As recently reported by Kondo et al, the use of chiral receptors is the key to discriminate chiral substances [89]. They used tetraamide-based receptors having chiral ʟ-serine and ʟ-threonine to discriminate enantiomers of N -acetyl amino acid anions through ratiometric fluorescence analysis.…”

Recognition of Chiral Carboxylates by Synthetic Receptors

“…In 2018, a paper was published on treating the chiral recognition of tetraamide fluorescent receptors 4 and 5 using the geometry of a diamide derivative of isophthalic acid (Figure 3) [25]. The ligands were designed to compare the enantiodiscrimination abilities of the chiral 1,3-diamide derivative of phthalic acid containing a five-membered cyclopentane ring 2 with the analogous 2,6-disubstituted pyridine derivative 1 and the effect of alkane ring size for the derivatives 1 and 3.…”