Absolute configuration of some dinorlabdanes from the copaiba oil

a novel ent-dinorlabdane (-)-13(r)-14,15-dinorlabd-8(17)-ene-3,13-diol was isolated from commercial copaiba oil along with two known dinorlabdanes. the absolute configuration of these dinorditerpenes was established for the first time through synthesis starting from known (-)-3-hydroxycopalic acid, which was also isolated from the same oleoresin.