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Stereostructure Assignment of Medium-Sized Rings through an NMR−Computational Combined Approach. Application to the New Germacranes Ketopelenolides C and D

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journal contribution
posted on 26.12.2008, 00:00 by Ernesto Fattorusso, Paolo Luciano, Adriana Romano, Orazio Taglialatela-Scafati, Giovanni Appendino, Marianna Borriello, Caterina Fattorusso
The new germacrane derivatives ketopelenolides C (2) and D (3) have been isolated from great mugwort (Artemisia arborescens). Their stereostructure elucidation exemplifies some of the most common pitfalls facing the configurational assignment of medium-sized polyfunctionalized compounds. It was established through a combined strategy including chemical derivatization, NMR data analysis, molecular modeling, and quantum-mechanical calculations including a comparison between experimental 13C NMR data and a Boltzmann-weighted average of DFT-calculated 13C NMR chemical shifts.