methyl(3aR,4R,5S,5aR,10bR,13aR)-4-(acetyloxy)-3a-ethyl-9-[(1aS,11S,13S,13aR)-1a-ethyl-11-(methoxycarbonyl)-1a,4,5,10,11,12,13,13a-octahydro-2H-3,13-methano-oxireno[9,10]azacycloundecino[5,4-b]indol-11-yl]-6-formyl-5-hydroxy-8-methoxy-3a,4,5,5a,6,11,12,13a-octahydro-1H-indolizino[8,1-cd]carbazole-5-carboxylate(formylleurosine),