Stereocontrolled total syntheses of (±)-pisiferic acid and (±)-O-methylpisiferic acid

A stereocontrolled approach to the construction of the angularly ester substituted trans-octahydrophenanthrene ring system related to diterpenes involving an aryl participated diazoketone cyclisation strategy is delineated. The tetrahydrophenanthrenone was prepared from the tetralone through the intermediates , , and . The formyl derivative of was treated with alkaline H2O2 to give the diacid which was converted into the diazomethyl ketone . Aryl participated cyclisation of afforded the enedione which was stereoselectively converted into the keto-ester . The transformation of into the diterpenes and has been efficiently accomplished.