“…Oxyfunctionalization of natural products is an effective method to obtain new biologically active compounds or valuable chiral building blocks for drug synthesis [13]. Oxidative transformations of levopimaric acid diene adducts, such as maleopimaric, fumaropimaric and quinopimaric acids, involved hydrogen peroxide [11,14], peracids [15], ozone [16 -18], osmium tetroxide, tertbutyl chromate [19] and permanganate oxidation [20]. The endoconfiguration of most Diels-Alder adducts appears to complicate access to the bridging double bond for common oxidizing agents.…”