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 magell anine-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-m ethylpiperidine ring-D from a cyclopentene precursor, e.g. 35-->38. Th e six-membered ring-A present in the natural products was constructed either through cationic enone-olefin cyclization (25-->26) or intramol ecular Michael addition (34-->35) protocols. Overall, the synthetic ef fort outlined here is notable for its brevity, conceptual simplicity a nd desirable levels of regio- and stereoselective control in various s teps. (C) 1998 Elsevier Science Ltd. All rights reserved.