Br-PEG1-acid

Br-PEG1-acid, is designed to provide a flexible polyethylene glycol spacer terminating in a bromide handle and a carboxylic acid functionality. Such bifunctional linkers are widely used to assemble targeted protein degradation constructs by enabling controlled conjugation to ligands and subsequent formation of stable PROTAC architectures. Its PEG-based segment supports favorable solubility and conformational mobility, which can improve coupling efficiency and help maintain productive geometry between the recruited target-binding moieties. The detailed structural and reactivity considerations are provided below.

Structure: Br-PEG1-acid features a short polyethylene glycol chain bearing a terminal bromide substituent and a terminal carboxylic acid group. The molecule contains ether linkages characteristic of PEG, a carbonyl within the acid, and a carbon–bromine bond suitable for substitution. Overall, it combines polar functionality with a reactive alkyl halide site.

Reactivity: The bromide enables nucleophilic substitution reactions commonly used in PROTAC synthesis, where nucleophiles such as amines or carboxylates can displace bromide under appropriate conditions. The carboxylic acid can be activated for amide bond formation using standard coupling chemistries, often employing carbodiimide-based activators and suitable bases. Typical solvents include polar aprotic media that support SN-type substitution and coupling efficiency, with temperature and stoichiometry adjusted to minimize side reactions and preserve ligand integrity.