Tos-PEG4-methyl ester contains tosyl and methyl ester moieties. The tosyl group can be easily replaced by thiol and amino group through a nucleophilic substitution.The hydrophilic PEG linker can increase the water solubility of the compound. Methyl ester can be hydrolyzed under mild basic condition to free acid, which readily reacts with amine to form amide bond under amide coupling conditions.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.