Predicting NMR Spectra by Computational Methods:  Structure Revision of Hexacyclinol

The structure of the natural product hexacyclinol was reassigned from endoperoxide 1 to the diepoxide 7 on the basis of calculated ¹³C chemical shift data using HF/3-21G geometries and mPW1PW91/6-31G(d,p) GIAO NMR predictions. These predictions correlate very well with experimental data for three other highly oxygenated natural products, elisapterosin B, maoecrystal V, and elisabethin A. Hexacyclinol is proposed to arise from acid-catalyzed rearrangement of panepophenanthrin in the presence of methanol.