The securinega alkaloids: Pursuing a versatile synthetic approach

© 2005 Societa Chimica Italiana. The Securinega alkaloids comprise a group of around thirty tetracyclic compounds isolated mainly from some plants of the Euphorbiacea family. Although some of these alkaloids have been known for more than forty years and they exhibit a remarkable biological activity, rather limited research has been published related to their syntheses. In this review, we summarise the different published approaches directed to these targets. Our own synthetic efforts culminate with the enantioselective synthesis of (-)-norsecurinine in nine steps and 11% overall yield. The crucial reactions of our last generation strategy are a palladium-catalysed enantioselective imide alkylation, a vinylogous Mannich reaction, and a ringclosing metathesis process. This approach is general for any antipode of the final target of either securinineor norsecurinine-type alkaloids.