2-(2S)-2-{[(5S)-1-(9H-fluoren-9-yl)-5-{3-[(azanylidene{[dioxo(2,2,4,6,7-pentamethyl-2,3-dihydro-1-benzofuran-5-yl)-λ6-sulfanyl]amino}methyl)amino]propyl}-3,6-dioxo-4-aza-2-oxahex-6-yl]amino}-5-[(azanylidene{[dioxo(2,2,4,6,7-pentamethyl-2,3-dihydro-1-benzofuran-5-yl)-λ6-sulfanyl]amino}methyl)amino]pentanoic acid