Issue 2, 2018

Differentiation of enantiomeric anions by NMR spectroscopy with chiral bisurea receptors

Abstract

Chiral anionic species are ubiquitous and play important roles in biological systems. Despite the recent advancements in synthetic anion receptors bearing urea functionalities, urea-based chiral solvating agents (CSAs) that can separate the NMR signals of racemic anions remain limited. Herein, three dibenzofuran-based C2-symmetric chiral bisureas were synthesized from the reaction of (R,R)-4,6-bis(1-aminopropyl)dibenzo[b,d]furan with phenyl isocyanate, phenyl thioisocyanate, or tosyl isocyanate. The chiral anion recognition properties of these bisureas were examined by 1H NMR spectroscopy using DL-tetrabutylammonium mandelate (TBAM) as a model substrate. A clear baseline separation of the enantiomeric signals of the benzylic proton of TBAM was achieved upon mixing with 0.5 equivalents of bis(phenylurea). In contrast to previous urea-based chiral anion receptors that differentiate the enantiomers of chiral anions by forming 1 : 1 host–guest complexes, a high chiral recognition ability of chiral bis(phenylurea) was achieved owing to the generation of an equilibrium between free guests, 1 : 1 host–guest complexes, and 1 : 2 host–guest complexes. Chiral bis(phenylurea) was also successfully employed in the separation of the enantiomeric 1H NMR signals of various racemic anions.

Graphical abstract: Differentiation of enantiomeric anions by NMR spectroscopy with chiral bisurea receptors

Supplementary files

Article information

Article type
Paper
Submitted
16 Sep 2017
Accepted
04 Nov 2017
First published
06 Nov 2017

Org. Biomol. Chem., 2018,16, 213-222

Differentiation of enantiomeric anions by NMR spectroscopy with chiral bisurea receptors

S. Ito, M. Okuno and M. Asami, Org. Biomol. Chem., 2018, 16, 213 DOI: 10.1039/C7OB02318A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements