ethyl 2-[6-(2,6-difluorophenyl)-4-oxo-5-aza-3-oxahex-5-yl]-5-[4-({[(4-{5-[6-(2,6-difluorophenyl)-4-oxo-5-aza-3-oxahex-5-yl]-3-[(dimethylamino)methyl]-4-(ethoxycarbonyl)thiophen-2-yl}phenyl)amino]methyl}amino)phenyl]-4-[(dimethylamino)methyl]thiophene-3-carboxylate