Multi-nuclear NMR of axially chiral biaryls in polypeptide orienting solvents: spectral discriminations and enantiorecognition mechanisms

Abstract : Due to the importance of axially chiral biaryl derivs. as chiral auxiliaries and/or ligands for asym. synthesis, as well as their structural role in bioactive natural products, continuous efforts have been undertaken to propose efficient methods for their atropo-selective synthesis. As a consequence, proposing robust and reliable anal. tools that are able to discriminate the spectral signal of atropisomeric enantiomers becomes crucial to evaluate the enantiomeric excesses of mixts. In this work, we show how several multi-nuclear 1D/2D-NMR techniques using homopolypeptide chiral liq. crystals as aligning solvents can provide a panel of anal. possibilities (through differences of chem. shift anisotropies, dipolar and quadrupolar residual couplings) to spectrally discriminate enantiomers of a large collection of trisubstituted axially chiral biphenyls. Approaches involving 31P, 13C and 2H 1D- or 2D-NMR expts. at natural abundance levels are explored. Among noteworthy results, the first examples of spectral enantiosepns. using 31P nuclei as nuclear probe are reported. Finally, the roles of electronic factors and shape anisotropy in the efficiency of chiral discrimination mechanisms are examd. and discussed. Mol. modeling calcns. were carried out to establish the electronic profile of these analytes in order to understand and rationalize the 13C-{1H} NMR results.
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Submitted on : Friday, October 4, 2019 - 11:03:46 PM
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Philippe Berdagué, Jose-Enrique Herbert-Pucheta, Vishwajeet Jha, Armen Panossian, Frederic Leroux, et al.. Multi-nuclear NMR of axially chiral biaryls in polypeptide orienting solvents: spectral discriminations and enantiorecognition mechanisms. New Journal of Chemistry, Royal Society of Chemistry, 2015, 39 (12), pp.9504-9517. ⟨10.1039/C5NJ01434D⟩. ⟨hal-02306236⟩

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