Collective Synthesis of Highly Oxygenated (Furano)germacranolides Derived from Elephantopus mollis and Elephantopus tomentosus.

Germacranolides, secondary metabolites produced by plants, have garnered academic and industrial interest due to their diverse and complex topology as well as a wide array of pharmacological activities. Molephantin, a highly oxygenated germacranolide isolated from medicinal plants, Elephantopus mollis and Elephantopus tomentosus, has exhibited antitumor, inflammatory, and leishmanicidal activities. Its chemical structure is based on a highly strained ten-membered macrocyclic backbone with an (E,Z)-dienone moiety, which is fused with an α-methylene-γ-butyrolactone and adorned with four successive stereogenic centers. Herein, we report the first synthesis of molephantin in 12 steps starting from readily available building blocks. The synthesis features the highly diastereoselective intermolecular Barbier allylation of the ß,γ-unsaturated aldehyde with optically active 3-bromomethyl-5H-furan-2-one intermediate and ensuing Nozaki-Hiyama-Kishi (NHK) macrocyclization for the construction of the highly oxygenated ten-membered macrocyclic framework. This synthetic route enabled access to another germacranolide congener, tomenphantopin F. Furthermore, cycloisomerization of molephantin into 2-deethoxy-2ß-hydroxyphantomolin could be facilitated by irradiation with ultraviolet A light (λmax=370 nm), which opened a versatile and concise access to the related furanogermacranolides such as EM-2, phantomolin, 2-O-demethyltomenphantopin C, and tomenphantopin C.

Withaferin A, a polyfunctional pharmacophore that includes covalent engagement of IPO5, is an inhibitor of influenza A replication.

Withaferin A, a natural steroidal lactone found in the extracts of Withania somnifera, is used extensively in traditional medicine and part of an ancient remedy in ayurvedic medicine. Prior investigations into its mode of action have shown withaferin to be a polyfunctional pharmacophore with the covalent engagement of a multitude of therapeutic targets. Herein, we report that withaferin A is also a covalent inhibitor of IPO5, an importin that translocates cargos from the cytosol to the nucleus. We show that withaferin inhibits influenza A replication in epithelial cells (A549). Using a panel of inhibitors that selectively recapitulate part of withaferin A's pharmacological profile (goyazensolide, withaferin A derivatives, FiVe1, and bardoxolone methyl), we show that IPO5 inhibition contributes to the influenza replication inhibition but is not essential for the observed activity of withaferin A. We show that bardoxolone methyl, a semisynthetic triterpenoid in clinical development to treat chronic kidney disease and that shares some of the pharmacological profile of withaferin, also inhibits influenza A replication effectively. The inhibitory activity against influenza A replication should stimulate further studies to repurpose this therapeutic.

Identification of a Covalent Importin-5 Inhibitor, Goyazensolide, from a Collective Synthesis of Furanoheliangolides.

Sesquiterpenes are a rich source of covalent inhibitors with a long history in traditional medicine and include several important therapeutics and tool compounds. Herein, we report the total synthesis of 16 sesquiterpene lactones via a build/couple/pair strategy, including goyasensolide. Using an alkyne-tagged cellular probe and proteomics analysis, we discovered that goyazensolide selectively targets the oncoprotein importin-5 (IPO5) for covalent engagement. We further demonstrate that goyazensolide inhibits the translocation of RASAL-2, a cargo of IPO5, into the nucleus and perturbs the binding between IPO5 and two specific viral nuclear localization sequences.