FR901464 is a potent anticancer natural product that lowers the mRNA levels of oncogenes and tumor suppressor genes. In this article, we report a convergent enantioselective synthesis of FR901464, which was accomplished in 13 linear steps. Central to the synthetic approach was the diene-ene cross olefin metathesis reaction to generate the C6-C7 olefin without the use of protecting groups as the final step. Additional key reactions include a Zr/Ag-promoted alkynylation to set the C4 stereocenter, a mild and chemoselective Red-Al reduction, a reagent-controlled stereoselective Mislow-Evans-type [2,3]-sigmatropic rearrangement to install the C5 stereocenter, a Carreira asymmetric alkynylation to generate the C4′ stereocenter, and a highly efficient ring-closing metathesis-allylic oxidation sequence to form an unsaturated lactone. The decomposition pathways of FR901464's right fragment were studied under physiologically relevant conditions. Facile epoxide opening by -elimination gave two enones, one of which could undergo dehydration via its hemiketal to form a furan. To prevent this decomposition pathway, a right fragment was rationally designed and synthesized. This analogue was 12 times more stable than the right fragment of the natural product. Using this more stable right fragment analogue, an FR901464 analogue, meayamycin, was prepared in 13 linear steps. The inhibitions of human breast cancer MCF-7 cell proliferation by synthetic FR901464 and meayamycin were studied, and the GI 50 values for these compounds were determined to be 1.1 nM and 10 pM, respectively. Thus, meayamycin is among the most potent anticancer small molecules that do not bind to either DNA or microtubule.

FR901464 is a natural product isolated from a bacterium source that activates a reporter gene, inhibits pre-mRNA splicing, and shows antitumor activity. We previously reported the development of a more potent analogue, meayamycin, through the total synthesis of FR901464. Herein, we report detailed structure-activity relationships of FR901464 that revealed the significance of the epoxide, carbon atoms in the left tetrahydropyran ring, the Z-geometry of the side chain, the 1,3-diene moiety, the C-4 hydroxy group, and the C2"-carbonyl group. Importantly, the methyl group of the acetyl substituent was found to be inessential, leading to a new potent analogue. Additionally, partially based on in vivo data, we synthesized and evaluated potentially more metabolically stable analogues for their antiproliferative activity. These structural insights into FR901464 may contribute to the simplification of the natural product for further drug development.

FR901464 is a potent antitumor natural product that binds to the splicing factor 3b complex and inhibits premRNA splicing. Its analogue, meayamycin, is two orders of magnitude more potent as an antiproliferative agent against human breast cancer MCF-7 cells. Here, we report the picomolar antiproliferative activity of meayamycin against various cancer cell lines and multidrug-resistant cells. Time-dependence studies implied that meayamycin may form a covalent bond with its target protein(s). Meayamycin inhibited pre-mRNA splicing in HEK-293 cells but not alternative splicing in a neuronal system. Meayamycin exhibited specificity toward human lung cancer cells compared with nontumorigenic human lung fibroblasts and retained picomolar growth-inhibitory activity against multidrug-resistant cells. These data suggest that meayamycin is a useful chemical probe to study premRNA splicing in live cells and is a promising lead as an anticancer agent.