Tos-PEG3-CH2CO2tBu

Tos-PEG3-CH2CO2tBu is a PEG linker containing a t-butyl ester and a tosyl group. The hydrophilic PEG spacer increases solubility in aqueous media. The t-butyl protected carboxyl group can be deprotected under acidic conditions. The tosyl group is a very good leaving group for nucleophilic substitution reactions.