156250-60-1 Dispiro[6,11b-(epoxymethano)-6a,9-methano-1H-cyclohepta[a]naphthalene-8(7H),1'-cyclobutane-2',8''(7''H)-[6,11b](epoxymethano)[6a,9]methano[1H]cyclohepta[a]naphthalene]-7,7''-dione,3,3''-bis(acetyloxy)-4,4''-bis[(acetyloxy)methyl]eicosahydro-5,5'',6,6''-te