Tandem Reaction of Tertiary Enamides as a Synthetic Strategy to Construct the Fused N-Pentacyclic Skeleton of Erythrina Alkaloid Derivatives.

An exquisite protocol to the synthesis of erythrina-related structural derivatives was developed, which is composed of a nucleophilic addition of tertiary enamides to ketonic carbonyls and the trapping of acyliminium by an aromatic unit. This protocol afforded a powerful method for the construction of diverse fused N-pentacyclic skeletons in high efficiency and excellent diastereoselectivity by just using different acid catalysts.