Structural analysis of 3-α-acetyl-20(29)-lupene-24-oic acid, a novel pentacyclic triterpene isolated from the gum resin of Boswellia serrata, by NMR spectroscopy

3alpha-Acetyl-20(29)-lupene-24-oic acid (1) was isolated from the gum resin of Boswellia serrata. Its presence evidently suggests, that the oxidosqualene triterpene pathway of Boswellia serrata closely resembles the biosynthetic route already found in other plants. Complete H-1 and C-13 spectral assignments were derived from 1D and 2D NMR spectra. This is the first compound with the lupene backbone combining a 3alpha-hydroxy or 3alpha-acetyl group with the 24-carboxyl group, a configuration which is typical of the classical boswellic acids. Copyright (C) 2003 John Wiley Sons, Ltd.