Abiespiroside A, an unprecedented sesquiterpenoid spirolactone with a 6/6/5 ring system from Abies delavayi - Yang, X W; Li, S M; Li, Y L; Wu, L; Xia, J H; Shen, Y H; Tian, J M; Wang, N; Liu, Y H; Zhang, W D (Eur J Org Chem, 2010)