Crystal structure and absolute configuration of sphaeropsidin A and its 6-O-p-bromobenzoate

The absolute configuration of sphaeropsidin A was confirmed by X-ray analysis of the toxin and its 6-O-p-bromobenzoyl derivative. Sphaeropsidin A is a tetracyclic pimarane diterpene produced by different pathogens of forest plants belonging to Diplodia spp. This compound has been long known for its phytotoxic, antimicrobial, and insecticidal activities and, more recently, studied for its promising activity against drug-resistant melanoma and kidney cancer. These studies showed that sphaeropsidin A can overcome apoptosis and multidrug resistance in cancer cells through the modulation of ion-transporter activity, which is an emerging approach to cancer treatment. The availability of sphaeropsidin’s X-ray crystal structure could facilitate its further chemical and biological studies in pursuit of its development as an anticancer agent.