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Synthesis of (-)-Longithorone A: Using Organic Synthesis to Probe a Proposed Biosynthesis

Carl A. Morales, Mark E. Layton, Matthew D. Shair and Kyriacos C. Nicolaou
Proceedings of the National Academy of Sciences of the United States of America
Vol. 101, No. 33 (Aug. 17, 2004), pp. 12036-12041
Stable URL: http://www.jstor.org/stable/3373085
Page Count: 6
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Synthesis of (-)-Longithorone A: Using Organic Synthesis to Probe a Proposed Biosynthesis
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Abstract

We present a full report of our enantioselective synthesis of (-)-longithorone A (1). The synthesis was designed to test the feasibility of the biosynthetic proposal for 1 put forward by Schmitz involving intermolecular and transannular Diels-Alder reactions of two [12]-paracyclophane quinones. We have found that if the biosynthesis does involve these two Diels-Alder reactions, the intermolecular Diels-Alder reaction likely occurs before the transannular cycloaddition. The intermolecular Diels-Alder precursors, [12]-paracyclophanes 38, 49, 59, and 60, were prepared atropselectively, providing examples of ene-yne metathesis macrocyclization. The 1,3-disubstituted dienes produced from the macrocyclizations represent a previously unreported substitution pattern for intramolecular ene-yne metathesis. Protected benzylic hydroxyl stereocenters were used as removable atropisomer control elements and were installed by using a highly enantioselective vinylzinc addition to electron-rich benzaldehydes 26 and 27.

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