BRUCEANTINOL NSC238177 Picras-3-en-21-oic acid, 13,20-epoxy-3,11,12-trihydroxy-15-[(4-hydroxy-3,4-dimethyl-1-oxo-2-pentenyl)oxy]-2,16-dioxo-, methyl ester, (11.beta.,12.alpha.,15.beta.(E))-