A new route toward 7-Oxo-13-hydroxy-8,11,13-podocarpatrienes from labdane diterpenes.

Trinorlabdane 1,5-diketones (7, 10a,b, 13a,b), which are easily prepared from labdane diterpenes, are directly converted into the corresponding 7-oxo-13-hydroxy-8,11,13-podocarpatrienes, immediate precursors of bioactive compounds, under basic treatment. Utilizing this strategy, the first enantiospecific synthesis of 13-hydroxy-8,11,13-podocarpatriene (20), a constituent of Taiwania cryptomerioides, was achieved starting from (-)-sclareol (5) after a seven-step sequence in 55% overall yield.