N-Me-N-bis(PEG4-acid) HCl salt linker contains a secondary methylamino group between the two end t-butyl ester groups. The secondary amine group and PEG spacer increase the aqueous solubility of the resulting compound. The t-butyl protected carboxyl group can be deprotected under acidic conditions to form a free acid, which can undergo amide coupling with primary and secondary amines in the presence of EDC, DCC or HATU, etc.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.