m-PEG3-S-PEG1-t-butyl ester contains two terminal carboxylic acid groups. The two carboxylic acid groups can undergo sequential amide coupling with primary/secondary amine groups using EDC, DCC or HATU activators. The PEG spacer provides additional water solubility of the compound.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.