Enantioselective and Chemoselective Optical Detection of Chiral Organic Compounds without Resorting to Chromatography

Enantiorecognition and resolution are of essential importance in many diverse areas of science. Whenever there arises a need to analyze/investigate enantiomers in different situations chromatography stands up in our minds immediately. Nevertheless, chemoselective and enantioselective recognition/discrimination (without going for separation) constitutes a different perception and requirement. The techniques using chiroptical sensing cause detection based on molecular interactions induced in different manners. Enantioselective sensing of monosaccharides in gamma-cyclodextrin assembly and by diboronic acid based fluorescent sensors, application of bi-naphthol and H8BINOL based sensors and dendrimers, metal-to-ligand charge transfer transitions in CD, exciton-coupled circular dichroism, surface enhanced Raman spectroscopy, and enantioselective indicator displacement sensor arrays for enantioselective recognition/detection of chiral organic compounds, such as amines, amino acids/alcohols, and hydroxycarboxylic acids have been discussed in progressive manner with mechanistic explanations, wherever available. Besides, the chiroptical vs LC approach has been discussed. The present paper is focused on certain different non-chromatographic optical techniques and aims to extend an understanding and a view to consider such techniques which have been successful in selective detection, and determination of absolute configuration and enantiomeric excess, (without resorting to separation vis-a-vis LC) and that have potential use in high-throughput chiral assay and combinatorial search for asymmetric catalysts and reagents. The focus is on successful discrimination of enantiomers without using chromatography. Chiroptical approaches for enantioselective and chemoselective detection and determination of absolute configuration and enantiomeric excess (ee). The techniques include chiroptical sensing (e.g., CD, ECD, ORD), and spectrometric methods (e.g., hyper-Rayleigh scattering (HRS), surface enhanced Raman scattering (SERS) spectroscopy, and enantioselective indicator displacement sensor arraysimage