Azido-PEG4-CH2CO2-t-Bu contains an azide group and a t-butyl ester. The azide group readily reacts with alkyne, BCN, DBCO through Click Chemistry to yield a stable triazole linkage. The deprotection of the t-butyl carboxyl group under acidic conditions affords a free carboxylic acid that can be used for coupling with amine-bearing molecules.
Axispharm offers 3000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.