The novel macrocyclic compounds as chiral solvating agents for determination of enantiomeric excess of carboxylic acids

Qualitative analysis of chiral alanine by UV-visible-shortwave near infrared diffuse reflectance spectroscopy combined with chemometrics

UV-vis-SWNIR DRS is firstly and successfully used to discriminate the chirality of compounds in powder with a good accuracy.

Enantiodiscrimination of carboxylic acids using the diphenylprolinol NMR chiral solvating agents

Enantiopure diphenylprolinols have been developed as effective and practical NMR chiral solvating agents for the enantiodiscrimination of diverse α-carboxylic acids.

Modified Kagan's amide: synthesis and application as a chiral solvating agent for hydrogen-bonding based chiral discrimination in NMR

A modified Kagan's amide, N-((S)-1-(3,5-bis(trifluoromethyl)phenyl)ethyl)-3,5-dinitrobenzamide has been designed, synthesized and screened as a Chiral Solvating Agent for discrimination of optically active substrates.

C-hexaphenyl-substituted trianglamine as a chiral solvating agent for carboxylic acids

Chiral hexaazamacrocycles with a trianglamine structure and C(3)-symmetry, containing six ring substituents and twelve stereocenters have been tested as chiral solvating agents (CSAs) for α-substituted carboxylic acids. Excellent results have been obtained with a hexaphenyl-substituted macrocycle. The optimal ratio between the macrocycle and racemic acid, allowing for baseline separation of the enantiomers' signals in the (1)H NMR spectrum, was dependent on the type of acid, in particular on its degree of acidity. The analyte and the CSA could be separated and recovered by a simple acid-base extraction and reused without purification. The conformations of the free and protonated hexaamino macrocycles were inferred by CD spectroscopic studies and DFT calculations.

A versatile and practical solvating agent for enantioselective recognition and NMR analysis of protected amines

The 3,5-dinitrobenzoyl-derived 1-naphthylethyl amide 3 is an attractive CSA for NMR analysis of protected amines. It is readily prepared in a single step and combines practical resolution of diastereomeric complexes due to signal sharpness and effective signal separation. Crystallographic analysis shows that 3 forms a chiral cleft that can selectively bind one enantiomer of a substrate through hydrogen bonding, π-π stacking, and CH/π interactions. The enantioselective complex formation causes strong upfield shifts in the (1)H NMR spectrum even in the presence of only 5 mol % of 3.

Synthesis of chiral calix[4]arenes bearing aminonaphthol moieties and their use in the enantiomeric recognition of carboxylic acids

Two armed chiral calix[4]arenes 8-16 functionalized at the lower rim with chiral aminonaphthol units have been prepared and the structures of these receptors characterized by FTIR, (1)H, and (13)C, DEPT and COSY NMR spectroscopy and elemental analysis. The enantioselective recognition of these receptors with various carboxylic acids has been studied by (1)H NMR and UV/Vis spectroscopy. The receptors exhibited different chiral recognition abilities towards the enantiomers of racemic materials and formed 2 : 1 or 1 : 1 complexes between host and guest. It was also demonstrated that chiral calix[4]arenes 9 and 16 could be used as chiral NMR solvating agents to determine the enantiomeric purity of mandelic acid.