The first synthesis of the marine natural product cyanogramide D is reported. The
key step is the acetylation of a β-carboline N-oxide, followed by acetyl migration. Since in this particular case it was not possible
to incorporate the styryl side chain by Buchwald coupling, a phenylethanolamine side
chain was attached, which was dehydrated with Martin’s sulfurane after assembly of
the tetracycle. Pentacyclic products were obtained under Appel conditions. The synthesis
will facilitate the exploration of the biomimetic oxidative spirocyclization of cyanogramide
D to the spirooxindole cyanogramide.
Key words
natural products - alkaloids - dehydration - heterocycles - ketene aminals - total
synthesis
