Ligustolide A and B, two novel sesquiterpenes with rare skeletons and three 1,10-seco-guaianolide derivatives from Achillea ligustica

Achillea ligustica afforded two novel sesquiterpene lactones with rare 5/6/5 skeletons, three 1,10-seco-guaianolides and a chlorine-containing sesquiterpene lactone as well as six known compounds, including two monoterpenes, two guaianolides, one eudesmane and one secocaryophyllene derivative. The structures of the compounds were elucidated by extensive application of one- and two-dimensional NMR spectroscopy.