High-throughput assay for determining enantiomeric excess of chiral diols, amino alcohols, and amines and for direct asymmetric reaction screening

Nat Protoc. 2020 Jul;15(7):2203-2229. doi: 10.1038/s41596-020-0329-1. Epub 2020 Jun 15.

Abstract

Determining enantiomeric excess (e.e.) in chiral compounds is key to development of chiral catalyst auxiliaries and chiral drugs. Here we describe a sensitive and robust fluorescence-based assay for determining e.e. in mixtures of enantiomers of 1,2- and 1,3-diols, chiral amines, amino alcohols, and amino-acid esters. The method is based on dynamic self-assembly of commercially available chiral amines, 2-formylphenylboronic acid, and chiral diols in acetonitrile to form fluorescent diastereomeric complexes. Each analyte enantiomer engenders a diastereomer with distinct fluorescence wavelength/intensity originating from enantiopure fluorescent ligands. In this assay, enantiomers of amines and amine derivatives assemble with diol-type ligands containing a binaphthol moiety (BINOL and VANOL), whereas diol enantiomers form complexes with the enantiopure amine-type fluorescent ligand tryptophanol. The differential fluorescence is utilized to determine the amount of each enantiomer in the mixture with an error of <1% e.e. This method enables high-throughput real-time evaluation of enantiomeric/diastereomeric excess (e.e./d.e.) and product yield of crude asymmetric reaction products. The procedure comprises high-throughput liquid dispensing of three components into 384-well plates and recording of fluorescence using an automated plate reader. The approach enables scaling up the screening of combinatorial libraries and, together with parallel synthesis, creates a robust platform for discovering chiral catalysts or auxiliaries for asymmetric transformations and chiral drug development. The procedure takes ~4-6 h and requires 10-20 ng of substrate per well. Our fluorescence-based assay offers distinct advantages over existing methods because it is not sensitive to the presence of common additives/impurities or unreacted/incompletely utilized reagents or catalysts.

MeSH terms

  • Amines / chemistry*
  • Amino Alcohols / chemistry*
  • Drug Evaluation, Preclinical / methods*
  • High-Throughput Screening Assays / methods*
  • Stereoisomerism

Substances

  • Amines
  • Amino Alcohols