N-Methyl-N'-(azido-PEG2-C5)-Cy5 is a polyethylene glycol (PEG)-based linker that incorporates an azide functionality. This linker is primarily utilized in the synthesis of proteolysis targeting chimeras (PROTACs)[1].
Azido-PEG2-t-butyl ester is a PEG derivative containing a t-butyl ester and an azide group. The hydrophilic PEG spacer increases solubility in aqueous media. Under acidic conditions, the t-butyl protected carboxyl group can be deprotected.