Synthesis of 15-methylene-eburnamonine from (+)-vincamine, evaluation of anticancer activity, and investigation of mechanism of action by quantitative NMR

Abstract

The biological role of installing a critical exocyclic enone into the structure of the alkaloid, (−)-eburnamonine, and characterization of the new chemical reactivity by quantitative NMR without using deuterated solvents are described. This selective modification to a natural product imparts potent anticancer activity as well as bestows chemical reactivity toward nucleophilic thiols, which was measured by quantitative NMR. The synthetic strategy provides an overall conversion of 40%. In the key synthetic step, a modified Peterson olefination was accomplished through the facile release of trifluoroacetate to create the requisite enone in the presence of substantial steric hindrance.

15‐Methylene‐Eburnamonine Kills Leukemic Stem Cells and Reduces Engraftment in a Humanized Bone Marrow Xenograft Mouse Model of Leukemia

“…20 Additional evaluation of 1 and 3 side-by-side in MDA-MB-231 (breast cancer), 20 LNCaP (prostate cancer), RPMI-8226 (myleoma), U266 (myeloma), and KMS-12BM (myeloma) cell lines 21 is shown in Table 1. To investigate further the cytotoxicity of 3 in leukemia cells, primary ALL, AML, and CLL cells were treated with varying doses of 3 and cell viability was assessed by calcein AM staining (Figure 2).…”

“…20 Subsequent studies showed that this functional group is not only required for activity but also susceptible to conjugation by reactive thiols. 21 In a similar fashion, this functional group imparts biological activity to another natural product, parthenolide ( 4 ), and this compound has been shown to eliminate LSCs by increasing intracellular reactive oxygen species (ROS) 8 and depleting intracellular glutathione levels. 26 To examine if the anti-leukemia properties of 3 were also related to these processes, we co-treated cells with 3 and the antioxidant, glutathione (Figure 4).…”

“…23 Additionally, 3 was shown to exert antiproliferative activity against human multiple myeloma, breast, and prostate cancer cell lines in vitro. 21 Herein, we show that (−)-15-methylene-eburnamonine ( 3 ) is cytotoxic against primary ALL, AML, and CLL cells and primary LSCs in vitro . Cytotoxicity appears to be attenuated by glutathione, suggesting the potential involvement of oxidative stress pathways.…”

“…19 Recently, we designed and synthesized (−)-15-methylene-eburnamonine ( 3 ) to impart antiproliferative activity through structural modification. 20 Specifically, the analogue 3 displays a critical enone group, 21 and this functional group imparts cytotoxic properties similar to other enone-bearing natural products, such as parthenolide ( 4 ) 22 and andrographolide ( 5 ). 23 Additionally, 3 was shown to exert antiproliferative activity against human multiple myeloma, breast, and prostate cancer cell lines in vitro.…”

Synthesis and antitumor activity of tetrahydrocarbazole hybridized with dithioate derivatives

“…Tetrahydrocarbazole ring can be considered as an isostere to b-carboline ring which is present in many naturally occurring anticancer agents, such as the vinca alkaloids, vincamine (III) and (-)-eburnamonine (IV) (Figure 1) isolated from the Madagascar periwinkle (Catharanthus roseus) [33][34][35] . Although (-)-eburnamonine (IV) was devoid of anticancer activity even at the high dose of 100 M, its synthetic analogue 15-methylene-eburnamonine (V) displayed in vitro micromolar activity against prostate and myeloma cell lines 36 . Furthermore, the marine alkaloid Eudistomin K (VI), isolated from the Caribbean ascidian Eudistoma olivaceum, demonstrated potent antitumor activity against L-1210, A-549, HCT-8 and P-388 cell lines 37,38 .…”