Azido-PEG4-CH2CO2-t-butyl ester is a PEG reagent containing an azide group and a t-butyl protected carboxyl group. The azide group enables Click Chemistry. The protected carboxyl group (COOH) prevents self coupling or polymerization under standard acid/amine or acid/hydroxyl coupling conditions. t-butyl ester can be deprotected by acidic or basic hydrolysis. The hydrophilic PEG spacer increases solubility in aqueous media.
