We report the first fluorescence-based assay for the rapid determination of the ee value of amines, amino alcohols, and amino acid esters. The method uses the self-assembly of 2-formylphenylboronic acid with a chiral diol and a chiral amine or derivatives (of unknown chirality) to produce two diastereomeric iminoboronates that differ in their fluorescence intensity and polarization. The approach allows for the accurate determination of the ee value of chiral amines with errors of just 1-2%. We believe that this application of orthogonal dynamic covalent self-assembly in the determination of the enantioselectivity will lead to the development of high-throughput procedures for the determination of chirality.

The present study highlights a sensing approach for opiates using acyclic cucurbituril (aCBs) sensors comprising four glycouril units terminated on both ends with naphthalene fluorophore walls. The connectivity between the glycourils and naphthalene rings largely defines the opening size of the cucurbituril cavity and its diameter. The large hydrophobic binding cavity is flexible and is able to adapt to guests of various size and topology. The recognition event between the aCBs and guests results in modification of the fluorescence of the terminal walls, a fluorescence response that can be used to sense the drugs of abuse morphine, heroin, and oxycodone as well as their metabolites. Molecular dynamics is employed to understand the nature of the binding interactions. A simple three sensor cross-reactive array enables the determination of drugs and their metabolites in water with high fidelity and low error. Quantitative experiments performed in urine using a new three-way calibration model allows for determination of drugs and their metabolites using one sensor from a single fluorescence reading.

A simple and efficient method for determination of the yield, enantiomeric/diasteriomeric excess (ee/de), and absolute configuration of crude chiral diols without the need of work-up and product isolation in a high throughput setting is described. This approach utilizes a self-assembled iminoboronate ester formed as a product by dynamic covalent self-assembly of a chiral diol with an enantiopure fluorescent amine such as tryptophan methyl ester or tryptophanol and 2-formylphenylboronic acid. The resulting diastereomeric boronates display different photophysical properties and allow for fluorescence-based ee determination of molecules containing a 1,2- or 1,3-diol moiety. This method has been utilized for the screening of ee in a number of chiral diols including atorvastatin, a statin used for the treatment of hypercholesterolemia. Noyori asymmetric hydrogenation of benzil was performed in a highly parallel fashion with errors <1 % ee confirming the feasibility of the systematic examination of crude products from the parallel asymmetric synthesis in real time and in a high-throughput screening (HTS) fashion.

A highly accurate and reliable screening method for enantiomeric excess of amine derivatives in the presence of water is reported. The fluorescence-based screening system has been realized by self-assembly of chiral diol-type dyes (BINOL, VANOL and VAPOL), 2-formylphenylboronic acid, and chiral amines forming iminoboronate esters. The structure and chirality of the amine analytes determine the stability of the diastereomeric iminoboronate esters, which in turn display differential fluorescence. The fluorescence signal reflects the enantiomeric purity of the chiral amines and was utilized in high-throughput arrays. The arrays were able to recognize enantiomeric excess of amines, amino esters, and amino alcohols. In addition to qualitative analysis, quantitative experiments were successfully performed. Studies of the role of additives such as water or citrate were carried out to gain insight into the stability of the iminoboronate esters. It is shown that the above additives destabilize less stable esters while the stable esters remain unchanged. Thus, the presence of water and citrate leads to increased difference between the diastereomeric iminoboronates and contributes to the enantiodiscrimination of the chiral amines.

Determination of enantiomeric excess (ee) in chiral compounds is a key step in the development of chiral catalyst auxiliaries and chiral drugs. Here, we describe a sensitive and robust fluorescence-based assay for the determination of ee in mixtures of enantiomers of 1,2-and 1,3-diols, chiral amines, amino alcohols, and amino acid-esters. The method is based on the dynamic self-assembly of commercially available chiral amines, 2formylphenylboronic acid, and chiral diols in acetonitrile to form diastereomeric fluorescent complexes. Each analyte enantiomer gives rise to a different diastereomer with a distinct fluorescence wavelength and intensity originating from the enantiopure fluorescent ligands. In this assay, enantiomers of amines and amine derivatives assemble with diol-type ligands containing bi-naphthol moiety (BINOL and VANOL), while diol enantiomers form complex with the enantiopure amine-type fluorescent ligand tryptophanol. This differential fluorescence can be utilized to determine the amount of each enantiomer in the mixture with errors below 1% ee. This method allows for the realtime evaluation of enantiomeric/diastereomeric excess (ee/de) and product yield of crude asymmetric reaction products in a high-throughput fashion. The only processes involved in 2 this protocol are high-throughput liquid dispensing of three components into 384-well plates and recording the fluorescence using automatic plate reader. Emergence of such high throughput approaches allows 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 3-4 hours to run and requires 10-20 ng of the substrate per well. Our fluorescencebased assay offers distinct advantages over existing traditional methods as it is not sensitive to the presence of common additives or impurities as well as unreacted/incomplete utilized reagents and catalysts.