Acanthospermal A

2-Hydroxy-2-methylpropionic acid (3aS,4S,5S,11aR,6E,10E)-6-formyl-2,3,3a,4,5,8,9,11a-octahydro-10-methyl-3-methylene-4-(2-methyl-1-oxopropoxy)-2-oxocyclodeca[b]furan-5-yl ester