Quantum Mechanical–NMR-Aided Configuration and Conformation of Two Unreported Macrocycles Isolated from the Soft Coral Lobophytum sp.: Energy Calculations versus Coupling Constants

Two new macrocyclic cembranoids were isolated from the South China Sea soft coral Lobophytum sp. Quantum mechanical–nuclear magnetic resonance (QM–NMR) methods were decisive in their structural elucidation. Better performance in arriving at definitive structures was obtained by QM–NMR methods upon incorporation of 3JHH values. The validity of this approach also supported an alternative conformational proposal versus that obtained by X-ray crystallography.We thank a reviewer for suggesting the comparative using the Xray structures. This research work was financially supported by the Natural Science Foundation of China (No. 81991521), the Drug Innovation Major Project (No. 2018ZX09711-001-001- 009). A.H.D thanks the CSIC for a JAE-intro grant to C.C.G. This study made use of the SGAI-CSIC supercomputing facilities. We thank M.H. Dorta for help with graphics edition and G. Jones, funded by Cabildo de Tenerife, TFinnova Programme supported by MEDI and FDCAN for English edition.Peer reviewe