HBr·H2N-O-(CH2)5-COOH

HBr·H₂N-O-(CH₂)₅-COOH is a hydrobromide salt-form heterobifunctional reagent designed for sequential conjugation via amine-mediated amidation and carboxyl-based coupling, particularly useful in peptide synthesis and small molecule modifications. Its key advantages include enhanced water solubility due to the salt form, a defined five-carbon spacer for reduced steric hindrance, and dual reactivity for flexible assembly, though the protonated amine may require neutralization for efficient nucleophilic reactions and the carboxyl group needs activation for amidation.