Elucidation of chiral Recognition mechanism of alpha-amino acids using ligand exchange high performance liquid chromatography

Abstract

A técnica de HPLC por troca de ligante foi utilizada para a separação de racematos de amino ácidos com cadeia lateral alifática. Para tanto, o seletor quiral escolhido foi o complexo de Cu(II) combinado com a L-fenilalananina. Os resultados mostram que o primeiro enanciômero a eluir foi a forma D, seguido da forma L. Segundo o conceito de interação de 3 pontos, foi proposto um mecanismo de reconhecimento quiral, no qual não há evidências de mudança de configuração após a formação dos complexos pseudo-homo e heteroquiral. Cálculos DFT-B3LYP para energia e espectro vibracional confirmaram a viabilidade deste mecanismo, pois mostram a que a configuração trans do complexo homoquiral é mais estável do que a forma cis.Ligand exchange HPLC technique was applied to resolve chiral separation of aliphatic side chain aminoacid racemates. Chiral selector was copper L-phenylalaninate (II) and the results showed the elution of D enantiomer followed by L form. Considering the 3-point interaction concept, a mechanism of chiral recognition was proposed, in which no change of configuration would follow the formation of pseudo-homochiral and heterochiral complexes. To prove the reliability of this mechanism, the trans configuration of homochiral complex had to be more stable than the cis form, which was confirmed by DFT-B3LYP calculation in gas phase. The infrared frequencies were also calculated and the comparison with the subtracted and deconvoluted spectrum of the in-solution complex also pointed to the presence of the trans diasteroisomer.

Chiral Mesoporous Silica Materials: A Review on Synthetic Strategies and Applications

“…As effective instrumental techniques for the separation of chiral enantiomers, high-performance liquid chromatography (HPLC) [ 81 ], gas chromatography (GC), thin-layer chromatography (TLC) [ 82 ] and capillary electrophoresis (CE) make great contributions and account for a great proportion [ 83 , 84 , 85 ]. Owing to the nematic structure, chirality, and large pore size of chiral nematic mesoporous silica (CNMS), it attracted considerable attention as a chiral stationary phase.…”

Amino acids as chiral selectors in enantioresolution by liquid chromatography

“…Later, the mechanism of chiral recognition was investigated theoretically for both isomers by DFT calculations in gas phase along with infrared spectra simulation in the 100–600/cm range, which corresponds to the bands assigned as metal–ligand vibrations; the trans configuration of homochiral complex was found to be more stable than the cis form, i.e. homochiral trans complex present in the mobile phase exchanges with l and d enantiomers, with greater retention of the l form (Senra et al ., ).…”

“…Later, the mechanism of chiral recognition was investigated theoretically for both isomers by DFT calculations in gas phase along with infrared spectra simulation in the 100-600/cm range, which corresponds to the bands assigned as metal-ligand vibrations; the trans configuration of homochiral complex was found to be more stable than the cis form, i.e. homochiral trans complex present in the mobile phase exchanges with L and D enantiomers, with greater retention of the L form (Senra et al, 2007). Chiral mobile phase containing the complex of Cu(II) with the optically active L-phenylalaninamide and an ion-pair reagent, sodium 1-octanesulfonate, was used for the separation of the three stereoisomers of octahydroindole-2-carboxylic acid (Oic, an intermediate in the synthesis of perindopril) on an RP-C 8 column with a flow rate of 1.0 mL/min and UV detection at 255 nm (Sun et al, 2006).…”

Stereoselective adsorption utilizingl-phenylalanine imprinting chiral ordered mesoporous silica

“…11,12 Moreover, L-phenylalanine (L-Phe) has been successfully applied to chiral chromatographic separation as chiral selector in the mobile phase. [13][14][15] Moreover, phenylalanine is a well-known a-amino acid that is essentially possessed by all humans in the L-conguration. Phenylalanine, contains benzene, amino and carboxylic acid moieties, which facilitates the formation of COMS through non-covalent multiple interactions, such as electrostatic and hydrophobic interactions, with silica resources and surfactants added.…”