Uragogin and blepharodin, unprecedented hetero-Diels–Alder adducts from Celastraceae species

Uragogin and blepharodin were isolated from Crossopetalum uragoga and Maytenus magellanica, respectively. They represent the first examples of a triterpene–neolignan ester and a heptacyclic arylpropanoid-nor-triterpenephenol, hetero-Diels–Alder adducts built with dioxane bridges. Their proposed biosynthetic route is discussed.