Synthetic Applications of 2-Cyano-1,2,3,6-tetrahydropyridines. 2. Synthesis of Isodasycarpidone and Related Systems, the Ervitsine Skeleton, and Its Benzo Analogue

Article abstract of DOI:10.1021/jo00209a031

The synthesis of isodasycarpidone (8a), N-demethylisodasycarpidone (9a), and their epi derivatives 8b and 9b is described.The condensation of an appropriate 2-cyano-1,2,3,6-tetrahydropyridine with indole and the conjugate addition of diethylcopper(I)-magnesium bromide to the resulting α,β-unsaturated esters constitute the key steps of this synthesis.A similar condensation from methyl 2-cyano-1-methyl-1,2,3,6-tetrahydropyridine-4-acetate (11) and indolylmagnesium iodide or (m-methoxyphenyl)magnesium bromide, followed by catalytic hydrogenation, hydrolysis, and PPA cyclization establishes synthetic routes to the tetracyclic framework (16) of the indole alkaloid ervitsine and its benzo analogue 19.