N-(Azido-PEG2)-N-Boc-PEG4-t-butyl ester is a very useful branched PEG reagent with a terminal azide group, Boc protected amine, and a terminal t-butyl ester. The azide groups is very reactive with alkyne such as DBCO, BCN and propargyl reagnet via Click Chemistry. The protected amine can be deprotected under acidic conditions, and the t-butyl protected carboxyl group can be deprotected under mild acidic conditions.
