81612-56-8 Picrasan-21-oic acid, 3,3'-((1,4-dioxo-1,4-butanediyl)bis(oxy))bis(13,20-epoxy-11,12-dihydroxy-15-(3-methyl-1-oxobutoxy)-2,16-dioxo-, dimethyl ester, (4xi,11beta,12alpha,15beta)-(4'xi,11'beta,12'alpha,15'beta)-