Concerted use of homo‐ and heteronuclear 2D NMR in the elucidation of the structure of a novel pentaester of 19‐hydroxyingol from Euphorbia marginata seeds

Homo‐ and heteronuclear 2D NMR techniques were used to elucidate the structure of a novel pentaester of 19‐hydroxyingol from Euphorbia marginata seeds. The diterpene skeleton was identified by 1 H 1D and 2D COSY spectra. Heteronuclear 2D 13 C 1 H shift correlation spectroscopy was used to assign the 13 C signals. The position of the esterified hydroxymethyl group at C‐10 was identified by NOE difference spectroscopy. The nature of the five ester groups and their corresponding positions on the diterpene skeleton were identified by a combination of long‐range 2D 13 C 1 H correlation experiments and 13 C spectra with 1 H selective decoupling.