5,7-Bis(acetyloxy)-6-hydroxy-6,9-dimethyl-3-methylene-2-oxo-2,3,3a,4,5,6,6a,7,9a,9b-decahydroazuleno[4,5-b]furan-4-yl 2-methyl-2-butenoate AIDS-139904 AIDS139904 Hydruntinolide C NSC650437