1550-95-4Relevant academic research and scientific papers
Chiral Recognition of Amino Acid Derivatives: An NMR Investigation of the Selector and the Diastereomeric Complexes
Spisni, Alberto,Corradini, Roberto,Marchelli, Rosangela,Dossena, Arnaldo
, p. 684 - 688 (1989)
A tetraamidic selector containing two chiral synthons ((S)-phenylalanine) spaced by a 3,6,9-oxadecanoyl bridge (Phe-3-O-TA) (1) was used as stationary phase in capillary GC to perform chiral resolution of N-TFA-amino esters.In this paper we report an investigation on the mechanism of chiral recognition by NMR spectroscopy (1D and 2D, COSY, NOESY, and J-resolved experiments and 13C relaxation times).First the conformation of the selector in CDCl3 and CD3OD was studied to evaluate the structural features that might justify the enantiomeric discrimination ability.Thenthe self-associations of the selector and of the enantiomers (S)- and (R)-methyl (2a,2b) and (S)- and (R)-n-butyl N-TFA-phenylalaninate (3a, 3b) were investigated at variable temperature and concentration in CDCl3.Finally, titration experiments were carried out to detect the sites of the binding interactions between the selector and the enantiomers.A simple recognition mode is proposed to account for both the enantioselectivity of the phase and the elution order of the enantiomers observed in GC (t'RS).This is the first spectroscopic study on the mechanism of chiral recognition in GC concerning the real phase and not a model system.
Are Highly Stable Covalent Organic Frameworks the Key to Universal Chiral Stationary Phases for Liquid and Gas Chromatographic Separations?
Cui, Yong,Jia, Wenyan,Li, Yanan,Yu, Ziyun,Yuan, Chen,Yuan, Li-Ming,Zi, Min
, p. 891 - 900 (2022/02/03)
High-performance liquid chromatography (HPLC) and gas chromatography (GC) over chiral stationary phases (CSPs) represent the most popular and highly applicable technology in the field of chiral separation, but there are currently no CSPs that can be used for both liquid and gas chromatography simultaneously. We demonstrate here that two olefin-linked covalent organic frameworks (COFs) featuring chiral crown ether groups can be general CSPs for extensive separation not only in GC but also in normal-phase and reversed-phase HPLC. Both COFs have the same 2D layered porous structure but channels of different sizes and display high stability under different chemical environments including water, organic solvents, acids, and bases. Chiral crown ethers are periodically aligned within the COF channels, allowing for enantioselective recognition of guest molecules through intermolecular interactions. The COF-packed HPLC and GC columns show excellent complementarity and each affords high resolution, selectivity, and durability for the separation of a wide range of racemic compounds, including amino acids, esters, lactones, amides, alcohols, aldehydes, ketones, and drugs. The resolution performances are comparable to and the versatility is superior to those of the most widely used commercial chiral columns, showing promises for practical applications. This work thus advances COFs with high stability as potential universal CSPs for chromatography that are otherwise hard or impossible to produce.
