Labdane diterpenes from Haplopappus illinitus.

@article{Faini2002LabdaneDF,
  title={Labdane diterpenes from Haplopappus illinitus.},
  author={Francesca Faini and Cecilia Labb{\'e} and Ren{\'e} Botello Torres and Giuliano Delle Monache and Franco delle Monache},
  journal={Natural product letters},
  year={2002},
  volume={16 4},
  pages={
          223-8
        }
}
A chemical study of aerial parts of Haplopappus illinitus afforded five labdane diterpenoids whose structures were elucidated by high field NMR spectroscopy and 2D techniques. Four of them are dicarboxylic acids previously reported as the corresponding dimethyl ester derivatives and the fifth is a new compound.