The structures and absolute configurations of macrophyllic acids A-E, fivenew rearranged eudesmane sesquiterpene acids from the bark of Inula macrophylla

Macrophyllic acids A-E, five novel sesquiterpene acids with a new rearrange d carbon skeleton, have been isolated from the bark of Inula macrophylla. T heir structures were determined on the basis of spectral evidence (especial ly by HREIMS and 2D NMR) as well as chemical transformations. The structure of macrophyllic acid A was finally confirmed by an X-ray analysis. The abs olute configuration of macrophyllic acid A was determined by appropriate ch emical conversion and the means of PGME. The possible biosynthetic pathway for macrophyllic acids A-E is also discussed. (C) 2000 Elsevier Science Ltd . All rights reserved.