Study on the Enantiomeric Recognition of Chiral Ureas Containing Amino Acid Units

doi:10.11938/cjmr20243141

Abstract

Abstract:

Recognition of chiral molecules is critical for the chemical and pharmaceutical industries. Three kinds of urea containing chiral centers (L-Phe-U, L-Ala-U and L-Val-U) were synthesized as chiral solvating agents (CSAs) to identify chiral organic carboxylic acids with different substituents, whose chiral anion recognition properties were further examined by NMR spectroscopy. In the presence of 4-dimethylaminopyridine (DMAP), enantiomeric signals of the benzylic C-H protons of mandelic acid were observed when mixed with L-Phe-U. The ΔΔδ values of the C_αH signals ranged from 2.4 to 16.0 Hz, and the enantiomer excess (ee) value of RS-rac-mandelic acid (rac-MA) can be determined accurately. It was found that the phenyl group contained in chiral solvating agents and the groups connected to the chiral carbon center of substrates would affect the separation of enantiomeric signals. Moreover, DOSY spectra reveal that the diffusion coefficients of rac-MA enantiomers differ in the chiral solvating agents, providing insights into the dynamics of chiral recognition.

Key words: nuclear magnetic resonance (NMR), chiral solvating agents, chiral carboxylic acid, enantiomeric recognition, chemical shift difference, enantiomeric excess

CLC Number:

O482.53

KOU Xinhui, ZHANG Yubing. Study on the Enantiomeric Recognition of Chiral Ureas Containing Amino Acid Units[J]. Chinese Journal of Magnetic Resonance, 2025, 42(3): 221-230.

Figures/Tables 7

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Table 1

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序号	手性化学位移试剂	ΔΔδ/Hz
1	L-Phe-U	15.2
2	L-Phe-U	9.6
3	L-Phe-U	2.4
4	L-Phe-U	11.2
5	L-Phe-U	0.64
6	L-Phe-U	2.4
7	L-ALa-U	3.2
8	L-ALa-U	4.0
9	L-ALa-U	3.6