2-Butenoic acid, 4-(3a,4,5,7,10,11-hexahydro-8,9-dihydroxy-3,3,11-trimethyl-13-(3-methyl-2-butenyl)-11-(4-methyl-3-pentenyl)-7,15-dioxo-1,5-methano-1H,3H,9H-furo(3,4-g)pyrano(3,2-b)xanthen-1-yl)-2-methyl-