Beilstein J. Org. Chem.2023,19, 764–770, doi:10.3762/bjoc.19.56
temperatures yielding mixtures of addition products. The structural elucidations of the formed compounds were achieved by NMR spectroscopy. Particularly, the γ-gaucheeffect and long-range couplings were instrumental in assigning the stereochemistry of the adducts. However, in a recent paper, Novitskiy and
erroneous mechanistic pathway.
Keywords: bromination; computational NMR; γ-gaucheeffect; NMR; NOE-Diff experiments; Introduction
Nuclear magnetic resonance (NMR) spectroscopy is one of the most important analytical tools used to determine the structure of organic compounds. NMR not only confirms the
proves that there is no W arrangement between the H5exo/H6exo protons and the H7 proton. The resonance signal of the protons H2 and H3 collapsed to triplet indicating the zigzag orientation of the relevant protons (Supporting Information File 1).
Structure proof using γ–gaucheeffect: The γ-gaucheeffect
Beilstein J. Org. Chem.2019,15, 2003–2012, doi:10.3762/bjoc.15.196
of H-15 with H-12 and other protons. As an alternative, OH-14 α configuration was deduced from the chemical shifts of C-12 and C-9, which experience a strong shielding γ-gaucheeffect for OH-14α configurations [21]. These data indicate a relative stereochemistry of irinan B matching withanolide F (5
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Graphical Abstract
Figure 1:
Withanolides from Physalis peruviana. A) Structures of the newly characterised truncated withanolid...