Abstract
Aerial parts of Centaurea scoparia Sieb. afforded a new chlorinated guaianolide with an unusual isobutyl structural feature, diain (1), together with three known guaianolides, janerin (2), cynaropicrin (3), and deacylcynaropicrin (4). Structural assignments of the isolated compounds are based on spectroscopic methods including 1D- and 2D-NMR spectroscopy as well as mass spectroscopy. New and revised H-1- and C-13-NMR data are reported.