Deoxyelephantopin

2-Methylpropenoic acid (3aR,4S,9R,11E,12aR)-2,3,3a,4,5,9,10,12a-octahydro-2,7-dioxo-11-methyl-3-methylene-7H-9,6-methenofuro[2,3-f]oxacycloundecin-4-yl ester