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Synthesis and Structural Reassignment of Pubescone
Koichiro Ota1, Shinnosuke Okazaki1, Hiroaki Miyaoka1
1School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan.
Abstract:
Pubescone, isolated from various plants since 2010, was originally assigned a unique 11(7→6)abeo-14-norcarabrane skeleton. However, our recent total synthesis of saniculamoid D revealed striking spectroscopic similarities between these compounds, suggesting misidentification of pubescone. To investigate this issue, we synthesized the originally proposed structure of pubescone. Considerable discrepancies between the synthetic and natural product data confirmed that the originally proposed structure was incorrect. Additionally, the 13C-NMR and specific rotation data for synthetic (4S,5S,6S,10S)-saniculamoid D showed excellent agreement with the reported data for natural pubescone. These findings conclusively demonstrate that the previously identified pubescone is, in fact, saniculamoid D. This study rectifies the widespread structural misidentification that has persisted for over a decade and emphasizes the importance of total synthesis in validating complex natural products.
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