2,5,10,13,18,21,26,29-Octaoxatriacontanedioic acid, 4,27-bis[[[[2-(dimethylamino)ethoxy]carbonyl]oxy]methyl]-12,19-bis[8-[[[[ 2-(dimethylamino)ethoxy]carbonyl]oxy]methyl]-15-methyl-3,6,11-trioxo-2