Boc–phenylglycine: a chiral solvating agent for the assignment of the absolute configuration of amino alcohols and their ethers by NMR

Synthesis, resolution, and absolute configuration determination of a vicinal amino alcohol with axial chirality. Application to the synthesis of new box and pybox ligands

New racemic vicinal amino alcohol derivatives with 4‐benzylidenecyclohexane skeleton and axial chirality have been prepared. A preparatively easy and efficient protocol for resolution of the N‐benzoylamino alcohol is described. Using a 250 × 20 mm (L × ID) Chiralpak® IA column, and the appropriate mixture of n‐hexane/ethanol/chloroform as eluent, both enantiomers of N‐benzoylamino alcohol 3 are obtained with >99% enantiomeric excess (ee) by successive injections of a solution of the racemic sample in chloroform. The obtained axially chiral vicinal amino alcohol is used to synthesize structurally novel bisoxazoline ligands in high yields.

Enantioselective Recognition of Racemic Amino Alcohols in Aqueous Solution by Chiral Metal-Oxide Keplerate {Mo132 } Cluster Capsules

Determining the relative configuration or enantiomeric excess of a substance may be achieved using NMR spectroscopy by employing chiral shift reagents (CSRs). Such reagents interact noncovalently with the chiral solute, resulting in each chiral form experiencing different magnetic anisotropy; this is then reflected in their NMR spectra. The Keplerate polyoxometalate (POM) is a molybdenum-based, water-soluble, discrete inorganic structure with a pore-accessible inner cavity, decorated by differentiable ligands. Through ligand exchange from the self-assembled nanostructure, a set of chiral Keplerate host molecules has been synthesised. By exploiting the interactions of analyte molecules at the surface pores, the relative configuration of chiral amino alcohol guests (phenylalaninol and 2-amino-1-phenylethanol) in aqueous solvent was establish and their enantiomeric excess was determined by 1 H NMR using shifts of ΔΔδ=0.06 ppm. The use of POMs as chiral shift reagents represents an application of a class that is yet to be well established and opens avenues into aqueous host-guest chemistry with self-assembled recognition agents.

A simple ternary ion-pair complexation protocol for testing the enantiopurity and the absolute configurational analysis of acid and ester derivatives

The ternary ion-pair complexation protocol for rapid testing of the enantiopurity and the assignment of absolute configurations of various acid and ester derivatives.

1H NMR discrimination of CHF4226.01 diastereoisomers in DMSO-d6

Two diastereoisomers CHF4226.01 (R, R) and CHF4232.01 (S, R), differing for a chiral center, have been studied to investigate their possible discrimination using NMR. 1D NMR and 2D NMR experiments, such as COSY, NOESY and ROESY, were performed on pure isomers and on the association complexes formed in the presence of the chiral reagent (S)-(-)-1-(2-napthyl)ethylamine (S-NEA). Moreover, computational studies, concerning conformational analysis and molecular dynamics, were started and supported the NMR results.

In tube determination of the absolute configuration of alpha- and beta-hydroxy acids by NMR via chiral BINOL borates

A simple NMR methodology, through the formation of chiral BINOL borates in the NMR tube, and that reunites the advantages of chiral derivatizing (CDAs) and chiral solvating agents (CSAs), is presented for the assignment of the absolute configuration of alpha- and beta-hydroxy acids.

The Assignment of the Absolute Configuration of Diethyl Hydroxy- and Aminophosphonates by 1H and 31P NMR Using Naproxen as a Reliable Chiral Derivatizing Agent

The assignment of the absolute configuration of hydroxy- and aminophosphonates by their double derivatization with commercially available naproxen is presented. The correlation between the spatial arrangement around the stereogenic carbon center and the signs of the DeltadeltaRS allows determination of the absolute configuration of hydroxy- and aminophosphonates by simple comparison of the 1H and 31P NMR spectra of the (R)- and (S)-naproxen ester or amide derivatives. Extensive conformational analysis (theoretical calculations, low-temperature experiments) supported by the NMR studies of structurally diverse naproxen esters and amides of hydroxy- and aminophosphonates proved that a simplified model can be successfully used.