Further Insight from Model Experiments into a Possible Scenario Concerning the Origin of Manzamine Alkaloids

Abstract

Without the isolation of intermediates, 5,6-dihydropyridinium salts and their nitrile derivatives were prepared as shown in the scheme. Cyclization in the presence of an aminopentadienal led to the formation of the AB ring system of the halicyclamines, or, under alternative conditions, the fused AB ring system of the manzamines. Tf=trifluoromethanesulfonyl.