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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
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/3373085
Page Count: 6
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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 -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, -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.
Proceedings of the National Academy of Sciences of the United States of America © 2004 National Academy of Sciences