ORGN 673 |
| An advanced intermediate (rac-2) to the highly oxygenated triterpene quassinoids was prepared in 14 steps from tetrahydrofuran. The key steps are three diene-transmissive Diels-Alder cycloadditions. Several features of this synthesis are noteworthy, including a successful Mitsunobu reaction on an allenylic alcohol, a rare [4 + 2] cycloaddition involving an enethiol ether dienophile, and complete control over all 10 chiral centers created. The introduction of the C8 carbon atom could be accomplished using an intramolecular cyclopropanation of the diazoketone rac-3. A synthetic route to non-racemic vinylallene 1 will also be discussed.
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Total Synthesis of Complex Molecules
8:00 AM-12:00 PM, Wednesday, August 22, 2007 BCEC -- 258A, Oral
Division of Organic Chemistry |
