Abstract
Three new eremophilane‐type sesquiterpenes, (6__β__,8__α__)‐6‐(acetyloxy)‐8‐hydroxyeremophil‐7(11)‐en‐12,8‐olide (1), (6__α__,8__α__)‐6‐hydroxyeremophil‐7(11)‐en‐12,8‐olide (2), and (6__α__,8__α__)‐6‐(acetyloxy)eremophil‐7(11)‐en‐12,8‐olide (3) ((8__α__)‐eremophil‐7(11)‐en‐12,8‐olide = (4a__R__,5__S__,8a__R__,9a__S__)‐4a,5,6,7,8,8a,9,9a‐octahydro‐3,4a,5‐trimethylnaphtho[2,3‐b]furan‐2(4__H__)‐one), besides the recently elucidated eremoligularin (4) and bieremoligularolide (5), as well as a new highly oxygenated monoterpene, rel‐(1__R__,2__R__,3__R__,4__S__,5__S__)‐p‐menthane‐1,2,3,5‐tetrol (12), together with six known constituents, i.e., the sesquiterpenes 6 and 7, the norsesquiterpenes 8–10, and the monoterpene 13, were isolated from the roots of Ligularia muliensis. In addition, an attempt to dimerize 1 to a bieremophilenolide (Scheme) resulted in the generation of the new derivative (6__β__,8__β__)‐6‐(acetyloxy)‐8‐chloroeremophil‐7(11)‐en‐12,8‐olide (11). The new structures were established by means of detailed spectroscopic analysis (IR, FAB‐, EI‐, or HR‐ESI‐MS as well as 1D‐ and 2D‐NMR experiments). Compounds 4 and 5 were evaluated for their antitumor effects in vitro (Table 3).