Inspired by the biosynthesis of sesquiterpene lactones (SLs), herein we report the asymmetric total synthesis of the germacrane ring (24). The synthetic strategy features a selective aldol reaction between β,γ-unsaturated chiral sulfonylamide 15a and aldehyde 13, as well as the intramolecular α-alkylation of sulfone 21 to construct a 10-membered carbocylic ring. The key intermediate 24 can be used to prepare the natural products costunolide and parthenolide (PTL), which are the key precursors for transformation into other SLs. Furthermore, the described synthetic sequences are amenable to the total synthesis of SL analogues, such as trifluoromethylated analogues 32 and 45. Analogues 32 and 45 maintained high activities against a series of cancer cell lines compared to their parent PTL and costunolide, respectively. In addition, 32 showed enhanced tolerance to acidic media compared with PTL. To our surprise, PTL and 32 showed comparable half-lives in rat plasma and in the presence of human liver microsomes.

Natural depsipeptide vinylamycin was reported to be an antibiotic previously. Herein we report vinylamycin to be active against K562 leukemia cells (IC = 4.86 μM) and be unstable in plasma (t = 0.54 h). A total of 24 vinylamycin analogues with modification of the OH group and chiral centers were generated via a combinatorial approach. The lead compound 1a was subsequently characterized as having the following: no antimicrobial activity, significantly higher plasma stability (t = 14.3 h), improved activity against K562 leukemia cells (IC = 0.64 μM), and up to 75% cell inhibition without significant toxicities in K562 cells xenograft zebrafish model. Furthermore, compound 1a maintained its activity against the breast cancer cell line MCF-7 under hypoxic conditions. In comparison, the activity of gemcitabine in the same hypoxic in vitro model of MCF-7 cells was 15-fold lower. Therefore, the present results demonstrate that 1a has great potential as an anticancer agent.

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A series of dithiocarbamate esters of parthenolide (PTL) was designed, synthesised, and evaluated for their anti- acute myelogenous leukaemia (AML) activities. The most promising compound 7l showed greatly improved potency against AML progenitor cell line KG1a with IC50 value of 0.7 μM, and the efficacy was 8.7-folds comparing to that of PTL (IC50 = 6.1 μM). Compound 7l induced apoptosis of total primary human AML cells and leukaemia stem cell (LSCs) of primary AML cells while sparing normal cells. Furthermore, 7l suppressed the colony formation of primary human leukaemia cells. Moreover, compound 12, the salt form of 7l, prolonged the lifespan of mice in two patient-derived xenograft models and had no observable toxicity. The preliminary molecular mechanism study revealed that 7l-mediated apoptosis is associated with mitogen-activated protein kinase signal pathway. On the basis of these investigations, we propose that 12 might be a promising drug candidate for ultimate discovery of anti-LSCs drug.