Bromo-PEG2-NHS ester

Bromo-PEG2-NHS ester is a bifunctional PEG-based linker designed for efficient conjugation in PROTAC construction, enabling reliable attachment of targeting ligands and facilitating controlled spatial presentation to recruited E3 ligases. Its NHS ester provides a well-established acylating handle for forming stable amide bonds, while the bromo functionality supports subsequent derivatization or coupling strategies. These features make it a practical building block for researchers optimizing linker length, solubility, and modular synthesis; the following points describe its structure and reactivity in detail below.

Structure: The molecule contains a short, flexible polyethylene glycol segment that imparts aqueous solubility and conformational mobility. It bears an N-hydroxysuccinimide ester for acyl transfer, and a bromo substituent that can act as a reactive electrophile. The structure includes ester and ether linkages typical of PEG scaffolds.

Reactivity: The NHS ester reacts under mild, aqueous-compatible conditions with primary amines to form amide bonds via nucleophilic acyl substitution, typically using buffered, low-to-moderate pH media to preserve NHS ester reactivity. Common solvents include water and polar organic co-solvents (e.g., DMF or DMSO) to aid solubilization. The bromo group can be engaged in nucleophilic substitution or related coupling steps using appropriate nucleophiles, often requiring controlled base and solvent selection to minimize side reactions.