Carbamic acid,[3-[2-[[[2-[[(1S)-1-(chloromethyl)-1,2-dihydro-5-hydroxy-3H-benz[e]indol-3-yl]carbonyl]-1H-indol-5-yl]amino]carbonyl]-1H-indol-1-yl]propyl]-,1,1-dimethylethyl ester