2-[2-[bis(carboxylatomethyl)amino]-3-[2-[bis(carboxylatomethyl)amino]ethyl-(carboxylatomethyl)amino]propoxy]-5-[(4-butylphenyl)methoxy]benzoate;2-[2-[2-[bis(carboxylatomethyl)amino]-3-[2-[bis(carboxylatomethyl)amino]ethyl-(carboxylatomethyl)amino]propoxy]-5-[(4-butylphenyl)methoxy]phenyl]acetate;2-[[2-[bis(carboxylatomethyl)amino]-3-(4-butoxy-2-oxidooxycarbonylphenoxy)propyl]-[2-[bis(carboxylatomethyl)amino]ethyl]amino]acetate;2-[[2-[bis(carboxylatomethyl)amino]-3-[4-[(4-butylphenyl)methoxy]-2-sulfonatophenoxy]propyl]-[2-[bis(carboxylatomethyl)amino]ethyl]amino]acetate;2-[[2-[bis(carboxylatomethyl)amino]-3-(2-decoxy-4,6-disulfonatophenoxy)propyl]-[2-[bis(carboxylatomethyl)amino]ethyl]amino]acetate;2-[2-[3-[[2-[carboxylatomethyl-[2-[carboxylatomethyl-[2-[carboxylatomethyl-[2-[3-[2-(carboxylatomethyl)-4-(2-methylpropoxy)phenoxy]propylamino]-2-oxoethyl]amino]ethyl]amino]ethyl]amino]acetyl]amino]propoxy]-5-(2-methylpropoxy)phenyl]acetate