Regioselective benzylic oxidation of aromatic abietanes: application to the semisynthesis of the naturally occurring picealactones A, B and C

Oxygenated aromatic abietanes are an important class of naturally occurring compounds in plants where they play specific ecological roles. However, limited availability from their natural sources hampers their exploitation for the development of new drugs to treat human diseases. Herein the benzylic oxidation of aromatic abietanes mediated by sodium chlorite and aqueous tert-butyl hydroperoxide is reported. The method is regioselective for 12-substituted derivatives and gives the 7-oxo products, in good yields. Moreover, it conveniently replaces the use of toxic chromium reagents for this transformation. Preparation of 7-oxo, 7-oxo-15-hydroperoxy and 7-oxo-15-hydroxy derivatives of other aromatic abietanes is also possible with this method. Furthermore, the reaction products were used as key intermediates for a short and facile semisynthesis of the naturally occurring picealactones A, B and C to disclose their anti-proliferative activity for the first time.