Total synthesis of (+/-)-lepadiformine via an amidoacrolein cycloaddition

[reaction: see text]. The total synthesis of the cytotoxin lepadiformine is described. The intermolecular cycloaddition of a 2-amidoacrolein with the dimethyl acetal of 4,6-heptadienal gave a cycloadduct that was strategically functionalized for elaboration of the tricyclic ring system. These steps include a diastereoselective addition of an organoytterbium reagent to an aldehyde, cyclization to the trans-perhydroquinoline substructure via a Mitsunobu reaction, and an iodine-promoted amine cyclization with an alkene to introduce the pyrrolidine ring.