Carpedilactones A–D, Four New Isomeric Sesquiterpene Lactone Dimers with Potent Cytotoxicity from Carpesium faberi

Four new isomeric sesquiterpene lactone dimers, carpedilactones A–D (1–4), were isolated from the acetonic extract of Carpesium faberi. Among them, 1–3 are the first three 2,4-linked exo-Diels–Alder adducts between a eudesmanolide dienophile and a guaianolide diene. The absolute configurations of 1–4 were unambiguously established by Cu Kα X-ray crystallographic analyses. Compounds 1–4 exhibited potent cytotoxicities against human leukemia (CCRF-CEM) cells with IC50 value of 0.14, 0.32, 0.35, and 0.16 μM, respectively.从烟管头草（Carpesium faberi）的丙酮提取物中分离得到4个新的异构倍半萜内酯二聚体，命名为烟管头草内酯A–D（1–4）。其中，化合物1–3为首例由桉烷内酯类亲双烯体与愈创木内酯类双烯体通过2,4位连接形成的外型狄尔斯-阿尔德（Diels-Alder）加合物。通过Cu Kα射线单晶衍射分析明确确定了化合物1–4的绝对构型。化合物1–4对人白血病CCRF-CEM细胞表现出强效的细胞毒性，其半数抑制浓度（IC50）分别为0.14、0.32、0.35和0.16 μM。