Premium
Structural analysis of pentacyclic triterpenes from the gum resin of Boswellia serrata by NMR spectroscopy
Author(s) -
Belsner Klaus,
Büchele Berthold,
Werz Udo,
Syrovets Tatiana,
Simmet Thomas
Publication year - 2003
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.1138
Subject(s) - chemistry , boswellia serrata , two dimensional nuclear magnetic resonance spectroscopy , stereochemistry , nuclear magnetic resonance spectroscopy , reagent , terpene , proton nmr , organic chemistry , medicine , alternative medicine , pathology
3α‐Acetyl‐β‐boswellic acid ( 1 ), 3α‐acetyl‐α‐boswellic acid ( 2 ), 3α‐acetyl‐9,11‐dehydro‐β‐boswellic acid ( 3 ), 3α‐acetyl‐9,11‐dehydro‐α‐boswellic acid ( 4 ) and 3α‐acetyl‐11‐keto‐β‐boswellic acid ( 5 ) were isolated from the gum resin of Boswellia serrata . 1D and 2D NMR (COSY45, HMQC, HMBC, ROESY) spectra at 500 MHz were used for shift assignments and structure verification. All boswellic acids investigated share the cis conformation at ring D/E and the 3α orientation of the acetyl ester group. Owing to high‐order spectra, NMR could not determine the exact conformation of H‐20/H‐30 of the β‐boswellic acids. 3α‐Acetyl‐β‐boswellic acid methyl ester ( 1 ′ ) was synthesized for experiments with a shift reagent, Eu(fod) 3 , that enhanced the resolution considerably. The oxygen atoms of the 3α‐acetyl group form the apparent complex binding site for the shift reagent. Copyright © 2003 John Wiley & Sons, Ltd.