Synthetic studies towards novel tetracyclic Lycopodium alkaloids: A synthesis of deoxymagellaninone

A short, novel, linear triquinane-based strategy, directed towards the synthesis of complex tetracyclic alkaloids of paniculatine and magellanine-type, and culminating in the synthesis of deoxymagellaninone 32 is delineated. The cornerstone of our approach was the utilization of the 'carbocycle-heterocycle equivalency' stratagem to generate the N-methylpiperidine ring-D from a cyclopentene precursor, e.g. 35-->38. The six-membered ring-A present in the natural products was constructed either through cationic enone-olefin cyclization (25-->26) or intramolecular Michael addition (34-->35) protocols. Overall, the synthetic effort outlined here is notable for its brevity, conceptual simplicity and desirable levels of regio- and stereoselective control in various steps. (C) 1998 Elsevier Science Ltd. All rights reserved.