Chiral Recognition of Carboxylates—Receptors, Analytical Tools, and More

Abstract

Mostc arboxylic acids, which are among the most common molecules in biological systems, are chiral. The enantiomers of these species are commonly distinguished in nature, but such recognitionh as provenq uite difficult to reproduce by using artificial receptors. Better knowledge of the chiral recognition of carboxylates is therefore crucial for af ullu nderstanding of host-guest phenomenai nn ature, and also for the design of new analytical devices.I nt his Focus Review we summarize andd iscuss the methods employed to evaluater eceptors, and present av ariety of structural designst hat have been utilized in chiral receptors. Some advanced functions of receptors in sensors and sensor arrays are also reviewed.

Recognition of Chiral Carboxylates by Synthetic Receptors

“…A major challenge has been to design a host structure that will selectively interact with the carboxylate ion [12]. Carboxylates are examples of anions with a pseudotrigonal shape, and their negative charge is delocalized mainly on two oxygen atoms.…”

Exploring Selectivity of 22 Acyclic Urea‐, Carbazole‐ and Indolocarbazole‐Based Receptors towards 11 Monocarboxylates

“…This relation alone is by far insufficient for useful discrimination between different carboxylates. In order to improve selectivity, additional interactions are necessary, which can be achieved by host‐shape manipulation so that guests of certain shape/geometry would be preferred . The receptor should not only be able to differentiate between similar carboxylates but also between other anionic species and be capable of overcoming solvent and counterion competition.…”

“…In order to improve selectivity, additional interactions are necessary, which can be achieved by host-shape manipulation so that guests of certain shape/geometry would be preferred. [5] The receptor should not only be able to differentiate between similar carboxylates but also between other anionic species and be capable of overcoming solvent and counterion competition. A large variety in the properties of carboxylates (basicity, chirality, hydrophobicity/hydrophilicity, polarizability, etc.)…”

“…A number of studies demonstrate good affinity and moderate selectivity of synthetic receptors towards different carboxylates. [5,6] However, to the best of the knowledge of the authors of this paper, a comprehensive analysis of structural features of carboxylates related to their binding to synthetic receptors is lacking. Binding char-tors influence the binding.…”

Synthesis and enantiomeric recognition studies of optically active 5,5-dioxophenothiazine bis(urea) and bis(thiourea) derivatives

“…The enantiomeric recognition of chiral carboxylic acids as carboxylates is advantageous, because carboxylic acids exist in their dissociated forms under physiological conditions. 13,21 The most frequently used chiral motifs in anion receptors are amino acid, BINOL, steroid and monosaccharide units, [2][3][4][5][6][7][8][9][10][11][12][13][14][19][20][21][22] but among others 1-arylethyl [24][25][26][27][28][29] moieties have also been applied as sources of chirality. These sensor molecules often contain urea and thiourea units as receptor parts, which have good hydrogen bond donating ability therefore high affinity toward anions.…”