Diastereoselective intramolecular nitroaldol entry to lycoricidine alkaloids

The alumina promoted 6-exo-trig intramolecular nitroaldol cyclization described proceeds in a highly diastereoselective manner via a proposed chelation controlled chair-like transition state, the major diastereomer having the correct relative configuration at three stereocentres as observed in the pancratistatin series of antitumor agents, in contrast to prior literature cyclization methods.