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

Abstract

<jats:title>Abstract</jats:title><jats:p>Homo‐ and heteronuclear 2D NMR techniques were used to elucidate the structure of a novel pentaester of 19‐hydroxyingol from <jats:italic>Euphorbia marginata</jats:italic> seeds. The diterpene skeleton was identified by <jats:sup>1</jats:sup>H 1D and 2D COSY spectra. Heteronuclear 2D <jats:sup>13</jats:sup>C<jats:sup>1</jats:sup>H shift correlation spectroscopy was used to assign the <jats:sup>13</jats:sup>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 <jats:sup>13</jats:sup>C<jats:sup>1</jats:sup>H correlation experiments and <jats:sup>13</jats:sup>C spectra with <jats:sup>1</jats:sup>H selective decoupling.