Acid-PEG4-t-butyl ester is a PEG linker containing a t-butyl protected carboxyl group with a terminal carboxylic acid. The terminal carboxylic acid can react with primary amine groups in the presence of activators (e.g. EDC, or HATU) to form a stable amide bond. The hydrophilic PEG spacer increases solubility in aqueous media. The t-butyl protected carboxyl group can be deprotected under acidic conditions.
Acid-PEG4-C2-Boc is a PEG- and Alkyl/ether-based PROTAC linker can be used in the synthesis of PROTACs for the inhibition of mTOR[1].
[1] Jennifer PITZEN , et al. C40-, c28-, and c-32-linked rapamycin analogs as mtor inhibitors. WO2019212990A1.