Euparotin

(Z)-2-Methyl-2-butenoic acid (3aR,6R)-3,3a,4,5,6aβ,7,9a,9bα-octahydro-7α,9aβ-dihydroxy-9-methyl-3-methylene-2-oxospiro[azuleno[4,5-b]furan-6(2H),2'-oxiran]-4α-yl ester