Enantioselective recognitions of chiral molecular tweezers containing imidazoliums for amino acids

Abstract

Two kinds of novel chiral molecular tweezers containing imidazoliums were synthesized from L-alanine, L-phenylalanine, and L-glutamic acid. They are constructed by the chiral imidazolium pincers and two different spacers which are 1,3-bis (bromomethyl)benzene and 2,6-bis(bromomethyl)pyridine, respectively. The enantioselective recognition of L- and D-amino acid derivatives by these molecular tweezers was investigated by UV spectroscopic titration experiments and good enantioselectivities were obtained, which are highly sensitive to whether the spacer has the binding site and the pincers has the other aromatic rings besides imidazolium ring. The host molecular 3b.2PF6- showed remarkable enantioselectivity for N-Boc protected histidine methyl ester, affording K(L)/K(D) of 5.10.

Syntheses and Highly Enantioselective Fluorescent Recognition of α‐Aminocarboxylic Acid Anions Using Chiral Oxacalix[2]arene[2]bisbinaphthes

“…The bisbinaphthyl‐based tweezers fluorescence sensors are found to carry out enantioselective fluorescence probe in the recognition of α‐aminocarboxylic acid derivatives. The compounds acted as a selective flurescence probe in the recognition of α‐aminocarboxylic acid anions with the dramatic change of fluorescence intensity . Following clusters pioneering work, the macrocyclic host molecules crown ethers have attacted increasing interest in recent years.…”

“…[22][23][24][25][26][27][28][29][30] Amongst many of the enantioselective methods under investigation, such as nuclear magnetic resonance (NMR), high-performance liquid chromatography, circular dichroism, especially the use of fluorescence has attracted a sizable interest because it can offer the advantages of real-time analysis, high sensitivity, multiple sensing modes, widely available instrumentation, and remote detection capabilities. [31][32][33][34][35][36][37] Several fluorescent sensors, including those developed within our group, have been reported to show high enantioselectivity in the recognition of mandelic acid and/or tartaric acid or -NH 2 protected by acetyl-group, Boc-group or benzoyl-group amino acid. [38][39][40] However, the enantioselective recognition of native a-aminocarboxylic acid is poor; therefore, the development of enantioselective fluorescent sensors for native a-aminocarboxylic acid has become a major challenge in this area.…”

“…The compounds acted as a selective flurescence probe in the recognition of a-aminocarboxylic acid anions with the dramatic change of fluorescence intensity. [31][32][33][34][35][36][37] Following clusters pioneering work, the macrocyclic host molecules crown ethers have attacted increasing interest in recent years. Owing to the fine-tuned cavity structures, the crown ethers can be an emerging generation for molecule recognition.…”

Chiral Heterocycle-Based Receptors for Enantioselective Recognition

“…Later Xie and coworkers [78,79] synthesized the imidazole-based chiral molecular tweezers (Scheme 28) spaced by 2,6-di(bromomethyl)-4-chlorophenol, 1,3-phenylenebis(methylene) and 2,6-pyridylenebis(methylene). The dibromide salts,158a-c.2Br − and 159a-c.2Br − were obtained by the direct quaternization of 157a-c with 2,6-di(bromomethyl)-4-chlorophenol or 1,3-bis(bromomethyl)benzene or 2,6-bis(bromomethyl)pyridine while the hexafluorophosphate salts 158a-c.2PF6 − and 159a-c.2PF6 − were prepared by the treatment with a saturated aqueous solution of NH4PF6.…”

“…The chiral discrimination of chiral molecular tweezers for amino acids or their derivatives (Tables 15 and 16) were evaluated by the UV-vis titration method. Later Xie and coworkers [78,79] synthesized the imidazole-based chiral molecular tweezers (Scheme 28) spaced by 2,6-di(bromomethyl)-4-chlorophenol, 1,3-phenylenebis(methylene) and 2,6-pyridylenebis(methylene).…”