Conformational analysis of longifolene
Pulmonary Disease, Chronic Obstructive
We describe the stable conformation of the tricyclic sesquiterpenoid, longifolene, by experimental NMR data and molecular mechanics calculations of the coupling constants. The flexible seven-membered ring of longifolene adopts a twist-chair conformation. Analysis of the coupling constants, particularly of the methylene protons in the cycloheptane ring moiety, agrees with this low-energy conformation. Low-temperature NMR experiments and nuclear Overhauser effect measurements indicate that there is a single exchange-averaged NMR spectrum that has the highest population of the most stable conformer. Copyright © Taylor & Francis Group, LLC.
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