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Title: Supramolecular Methods for the Rapid Determination of Enantiomeric Excess
Abstract: The need for increasingly user-friendly and rapid assays for ee has arisen recently due the advent of parallel synthesis protocols for asymmetric reaction discovery and optimization. Many studies require hundreds to thousands of assays per day. A primary goal of our group is to design and implement high-throughput screening (HTS) assays for enantiomeric excess (ee) and reaction yield in catalytic asymmetric reaction screening. Our approach to the HTS of ee combines supramolecular chemistry, dynamic covalent bonding, and analytical instrumentation. We create very simple synthetic receptors or assemblies that are targeted to classes of chiral functional groups, and record absorbance or circular dichroism spectra for diastereomeric or enantiomeric complex formation. The analysis is performed in microtiter plates where the ee values of 96 crude reaction mixtures can be read within 10 minutes to 2 hrs depending upon the particular assay. Assays for diols, amines, carboxylic acids, ketones, and alcohols have been created. Several of these assays have been utilized in collaborations with synthetic methodology chemists throughout the nation. Examples of the assays, the physical organic underpinnings, along with practical applications will be presented.