| 16388646 |
Juhl M, Nielsen TE, Le Quement S, Tanner D: Synthesis of the zoanthamine ABC ring system: some surprises from intramolecular Diels-Alder reactions. J Org Chem. 2006 Jan 6;71(1):265-80.
[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. |
1(0,0,0,1) |