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Article Abstract
[chemical reaction: see text]. An advanced intermediate 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.
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