Biomacromolecule-Assisted Screening for Reaction Discovery and Catalyst Optimization

Circular Dichroism Sensing: Strategies and Applications

The analysis of the absolute configuration, enantiomeric composition, and concentration of chiral compounds are frequently encountered tasks across the chemical and health sciences. Chiroptical sensing methods can streamline this work and allow high-throughput screening with remarkable reduction of operational time and cost. During the last few years, significant methodological advances with innovative chirality sensing systems, the use of computer-generated calibration curves, machine learning assistance, and chemometric data processing, to name a few, have emerged and are now matched with commercially available multi-well plate CD readers. These developments have reframed the chirality sensing space and provide new opportunities that are of interest to a large group of chemists. This review will discuss chirality sensing strategies and applications with representative small-molecule CD sensors. Emphasis will be given to important milestones and recent advances that accelerate chiral compound analysis by outperforming traditional methods, conquer new directions, and pioneering efforts that lie at the forefront of chiroptical high-throughput screening developments. The goal is to provide the reader with a thorough understanding of the current state and a perspective of future directions of this rapidly emerging field.

Synthesis of N-Tosyl Allylic Amines from Substituted Alkenes via Vanadoxaziridine Catalysis

Herein, we report the catalytic allylic amination of α-methylalkenes with V2O3Dipic2(HMPA)2 and chloramine T as the quantitative source of N. The reaction works with high yields and stereoselectivities for α-methylalkenes. A proposed tosylnitrene-free catalytic cycle involving the formation of vanadoxaziridine complex 1 as the active catalyst and aminovanadation across the substrate as the rate-determining step has been proposed. Initial kinetic and competition experiments provide evidence for the proposed mechanism.

Chemometric sensing of stereoisomeric compound mixtures with a redox-responsive optical probe

The analysis of mixtures of chiral compounds is a common task in academic and industrial laboratories typically achieved by laborious and time-consuming physical separation of the individual stereoisomers to allow interference-free quantification, for example using chiral chromatography coupled with UV detection. Current practice thus impedes high-throughput and slows down progress in countless chiral compound development projects. Here we describe a chemometric solution to this problem using a redox-responsive naphthoquinone that enables chromatography-free click chemistry sensing of challenging mixtures. The achiral probe covalently binds amino alcohols within a few minutes at room temperature and generates characteristic UVA and CDA spectra that are intentionally altered via sodium borohydride reduction to provide a second, strikingly different chiroptical data set (UVB and CDB). Chemometric partial least squares processing of the chiroptical outputs then enables spectral deconvolution and accurate determination of individual analyte concentrations. The success of this approach is demonstrated with 35 samples covering considerably varied total analyte amounts and stereoisomeric ratios. All chemicals and machine learning algorithms are readily available and can be immediately adapted by any laboratory.