Picras-3-en-21-oic acid, 3,3'-((1,3-dioxo-1,3-propanediyl)bis(oxy))bis(13,20-epoxy-11,12-dihydroxy-15-((3-methyl-1-oxo-2-butenyl)oxy)-2,16-dioxo-, dimethyl ester, (11beta,12alpha,15beta)-(11'beta,12'alpha,15'beta)-)