TY - JOUR
T1 - Multi-nuclear NMR of axially chiral biaryls in polypeptide orienting solvents
T2 - Spectral discriminations and enantiorecognition mechanisms
AU - Berdagué, Philippe
AU - Herbert-Pucheta, Jose Enrique
AU - Jha, Vishwajeet
AU - Panossian, Armen
AU - Leroux, Frédéric R.
AU - Lesot, Philippe
N1 - Publisher Copyright:
© The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
PY - 2015/9/9
Y1 - 2015/9/9
N2 - Due to the importance of axially chiral biaryl derivatives as chiral auxiliaries and/or ligands for asymmetric 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 analytical tools that are able to discriminate the spectral signal of atropisomeric enantiomers becomes crucial to evaluate the enantiomeric excesses of mixtures. In this work, we show how several multi-nuclear 1D/2D-NMR techniques using homopolypeptide chiral liquid crystals as aligning solvents can provide a panel of analytical possibilities (through differences of chemical 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 experiments at natural abundance levels are explored. Among noteworthy results, the first examples of spectral enantioseparations 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 examined and discussed. Molecular modeling calculations were carried out to establish the electronic profile of these analytes in order to understand and rationalize the 13C-{1H} NMR results.
AB - Due to the importance of axially chiral biaryl derivatives as chiral auxiliaries and/or ligands for asymmetric 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 analytical tools that are able to discriminate the spectral signal of atropisomeric enantiomers becomes crucial to evaluate the enantiomeric excesses of mixtures. In this work, we show how several multi-nuclear 1D/2D-NMR techniques using homopolypeptide chiral liquid crystals as aligning solvents can provide a panel of analytical possibilities (through differences of chemical 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 experiments at natural abundance levels are explored. Among noteworthy results, the first examples of spectral enantioseparations 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 examined and discussed. Molecular modeling calculations were carried out to establish the electronic profile of these analytes in order to understand and rationalize the 13C-{1H} NMR results.
UR - http://www.scopus.com/inward/record.url?scp=84947976664&partnerID=8YFLogxK
U2 - 10.1039/c5nj01434d
DO - 10.1039/c5nj01434d
M3 - Artículo
AN - SCOPUS:84947976664
SN - 1144-0546
VL - 39
SP - 9504
EP - 9517
JO - New Journal of Chemistry
JF - New Journal of Chemistry
IS - 12
ER -