Synthesis of the zoanthamine ABC ring system: some surprises from intramolecular Diels-Alder reactions.
[reaction: see text] In connection with the total synthesis of the marine alkaloids zoanthamine and norzoanthamine, an elaborate model study was conducted starting from (-)-carvone. In nine steps alkenyl iodides corresponding to the C11-C24 fragment of zoanthamine were obtained. The alkenyl iodides were coupled to various stannanes (C6-C10 fragment) via the Corey modification of the Stille reaction, affording a variety of Diels-Alder precursors. An interesting and highly unexpected cascade reaction sequence was observed during the screening of an intramolecular Diels-Alder reaction, generating a novel tetracyclic framework. A slight modification in the Diels-Alder precursor allowed the desired cycloaddition to take place, giving the cycloadduct in 87% yield.
Juhl
Martin
M
Department of Chemistry, Technical University of Denmark, Building 201, Kemitorvet, DK-2800 Kgs. Lyngby, Denmark.
Nielsen
Thomas E
TE
Le Quement
Sebastian
S
Tanner
David
D
D000470:Alkaloids / Q000138:chemical synthesis / Q000737:chemistry; D001381:Azepines / Q000138:chemical synthesis / Q000737:chemistry*; D006576:Heterocyclic Compounds, 4 or More Rings / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D011804:Quinolines / Q000138:chemical synthesis / Q000737:chemistry*
D000470:Alkaloids; D001381:Azepines; D006576:Heterocyclic Compounds, 4 or More Rings; D011804:Quinolines; C400280:norzoanthamine