Tos-PEG9-t-butyl ester

Tos-PEG9-t-butyl ester 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.