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Carbon‐13 nuclear magnetic resonance spectra of brominated catechin derivatives: Stereoelectronic effects on chemical shifts
Author(s) -
Kiehlmann E.,
Tracey A. S.
Publication year - 1988
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260260306
Subject(s) - chemistry , steric effects , chemical shift , chloroform , acetone , bromine , resonance (particle physics) , medicinal chemistry , nmr spectra database , ring (chemistry) , catechin , hydrogen , oxygen , nuclear magnetic resonance spectroscopy , stereochemistry , spectral line , photochemistry , organic chemistry , polyphenol , antioxidant , physics , particle physics , astronomy
The 13 C NMR spectra of 21 catechin derivatives substituted at C‐6/C‐8 by bromine and/or hydrogen and at oxygen by methyl, acetyl and/or hydrogen have been analysed in deuteriated acetone and chloroform. When a methoxy group is flanked by two bulky ortho substituents (6‐Br and C‐4), the MeO and ortho/para ring carbons (C‐4a, C‐6, C‐8) are deshielded owing to steric inhibition of resonance, which permits a distinction between 6‐ and 8‐substituted catechin methyl ethers. Hindered acetoxy groups do not give rise to this phenomenon.