ORGN 860 |
| Amaryllidaceae lycorine-type alkaloids 3 continue to fuel numerous synthetic studies for their unique ABCD tetracyclic skeleton, which is known for its potentially useful pharmacological properties. This polycyclic structure is biosynthetically obtained via a one-electron oxidation of a diphenolic precursor, but such a radical reaction suffers a lack of regiochemical control and competing polymerization processes. Our interest in the two-electrons oxidative dearomatization of phenols mediated by iodine(III)-based reagent led us to envisage the elaboration of the key-intermediate 2: a chiral orthoquinone monoketal moiety (cycle C) induced a regio- and stereochemically-controlled N-C bond creation via an intramolecular Michael-type addition reaction. Subsequent trapping of the resulting enolate by an electrophilic orthoquinol acetate entity (cycle A) allowed the C-C bond formation. In this context a challenging ionic domino cyclization was also investigated.
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Total Synthesis of Complex Molecules
8:00 AM-12:00 PM, Thursday, 14 September 2006 Moscone Center -- Room 134, Oral
Division of Organic Chemistry |
