(6R)-N-[(2S)-4-amino-1-{[(2S,3R)-1-{[(2S)-4-amino-1-oxo-1-{[(3S,6R,9S,12S,15S,18S,21S)-6,9,18-tris(2-aminoethyl)-15-benzyl-3-[(1R)-1-hydroxyethyl]-12-(2-methylpropyl)-2,5,8,11,14,17,20-heptaoxo-1,4,7,10,13,16,19-heptaazacyclotricosan-21-yl]amino}butan-2-