Dolabrane-Type Diterpenoids with Immunosuppressive Activity from Koilodepas hainanense .

Thirteen new dolabrane-type diterpenoids, koilodenoids A-M ( 1 - 13 ), including a chlorinated congener ( 2 ), along with six known analogues, were isolated from Koilodepas hainanense . The structures were determined by analysis of spectroscopic data, ECD spectra, and X-ray crystallographic studies. The absolute configuration of C-15 in the 15,16-diol unit of compounds 4 and 5 was established by using the dimolybdenum tetraacetate [Mo ₂ (AcO) ₄ ]-induced ECD method. Compounds 4 , 7 , 16 , 17 , and 19 showed moderate to significant immunosuppressive activities against the proliferation of T and B lymphocytes in vitro , with compound 16 being the most potent (IC ₅₀ 0.86 and 0.29 μM, respectively).