Two‐dimensional INADEQUATE 13C NMR studies of maleopimaric acid, the diels–alder adduct of levopimaric acid and maleic anhydride, and of abietic acid

Abstract Two‐dimensional INADEQUATE 13 C NMR was used to establish firmly the carbon‐carbon connectivities present in abietic acid and maleopimaric acid, i.e. the adduct of levopimaric acid and maleic anhydride. This information leads to unambiguous assignments for the 20 and 24 carbon resonances of abietic acid and maleopimaric acid, respectively. Proton‐carbon chemical shift correlation and NOE experiments further revealed the three‐dimensional structure of maleopimaric acid.