Bromo-PEG1-CH2CO2H is a PEG linker containing a bromide 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 bromide (Br) is a very good leaving group for nucleophilic substitution reactions.
Bromo-PEG1-CH2COOH is a PROTAC linker can be used in the synthesis of PROTACs[1].
[1] Christopher Michael Semko, et al. C26-linked rapamycin analogs as mtor inhibitors. WO2019212991A1.