Propargyl-PEG6-Br

Propargyl-PEG6-Br is a bromo-terminated, PEG-based linker designed to support modular PROTAC assembly by enabling orthogonal conjugation to ligands while maintaining favorable solubility and conformational flexibility. Its ether-rich poly(ethylene glycol) backbone helps reduce aggregation and supports efficient linker presentation in targeted protein degradation workflows. The following sections describe its structural features and practical reactivity considerations for constructing PROTACs with this linker.

Structure: Propargyl-PEG6-Br contains a terminal bromoalkyl group for electrophilic functionalization and a propargyl handle for alkyne-based coupling. The PEG segment provides multiple ether linkages, enhancing polarity, hydration, and flexibility. The molecule is characterized by C–Br, C–C, and C≡C bonds, typically yielding a soluble, linker-like scaffold.

Reactivity: The bromo terminus is suitable for nucleophilic substitution reactions with heteroatom or carbon nucleophiles under conditions commonly used for alkyl bromides, enabling installation of the linker onto PROTAC ligand fragments. The terminal alkyne supports widely used click-type conjugations (e.g., copper-catalyzed azide–alkyne cycloaddition) or related alkyne-reactive coupling strategies. Choice of solvent and base is typically guided by ligand stability and nucleophile strength.