Utility of crown ethers derived from methyl β-d-galactopyranoside and their lanthanide couples as chiral NMR discriminating agents

Chiral NMR discrimination of amines: Analysis of secondary, tertiary, and prochiral amines using (18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid

“…Steric or electrostatic effects between the substituent groups of the tertiary amine and 1 provide the potential for a third point of interaction required for chiral recognition. 23 Relatively modest enantiomeric discrimination is observed in the 1 H and/or 13 C NMR spectra of most tertiary amines we examined in the presence of 1. Therefore tertiary amines associate with 1 and the substituent groups of the two enantiomers must interact differently with the crown ether.…”

“…All 1 H (16 scans, sweep width of 20.7 ppm, digital resolution of 18, pulse angle of 308, delay time of 1 sec) and 13 C spectra (4096 scans, sweep width of 238.3 ppm, digital resolution of 17, pulse angle of 308, delay time of 1 sec) were collected on a 400 MHz NMR spectrometer. Spectra were run in methanol-d 4 at ambient probe temperature and calibrated using tetramethylsilane as an internal reference.…”

Calix[4]arene, calix[4]resorcarene, and cyclodextrin derivatives and their lanthanide complexes as chiral NMR shift reagents

“…12,13 Consequently, ytterbium(III)nitrate was added to several of the methanol-soluble mixtures and shifting and broadening of the calixarene resonances occurred. Only the mixture of 15 with the sodium salt of 2 showed any Yb(III)-induced shifts in the spectrum of the substrate.…”

“…Enhancements in discrimination can occur because of the diastereomeric nature of the Ln-CSA-E complexes and/or because one enantiomer has a larger association constant with the CSA. We have described systems in which lanthanide ions have been bonded to cyclodextrins through a diethylenetriaminepentaacetic acid (DTPA) moiety, 10,11 to chiral crown ethers that have carboxylic acid or ␤-diol groups, 12,13 and to chiral carboxylate species derived from amino acids. 14,15 Cyclodextrins are especially significant since they are one of the few systems that are effective for the enantiomeric discrimination of watersoluble compounds.…”

Molecular tweezers for enantiodiscrimination in NMR: Di‐(R,R)‐1‐[10‐(1‐hydroxy‐2,2,2‐trifluoroethyl)‐9‐anthryl]‐2,2,2‐trifluoroethyl benzenedicarboxylates

“…Some chiral solvating agents are macrocyclic host compounds, like cyclodextrins 7,8 and crown ethers. 9,10 On the other hand, noncyclic compounds with flexibly sized cavities, which are frequently defined as molecular tweezers or clips, proved to be effective synthetic receptors. These compounds are characterized by having two aromatic groups, separated by a semi-rigid spacer, which enhances the selective binding with aromatic guests by p interactions.…”