Mal-PEG2-NH-Boc

Mal-PEG2-NH-Boc is a PEG-based bifunctional linker designed for assembling PROTACs that require controlled spatial separation and efficient conjugation between a targeting ligand and an E3-recruiting moiety. Its maleimide handle enables selective coupling to thiol-bearing partners, while the protected amine provides a stable functional outlet for subsequent bond formation. These features support modular PROTAC synthesis and help maintain favorable linker flexibility; detailed structural and reactivity considerations are provided below.

Structure: Mal-PEG2-NH-Boc contains a maleimide electrophile conjugated to a short poly(ethylene glycol) segment, providing a flexible, hydrophilic spacer. The linker incorporates an amine protected as a Boc carbamate, and features amide/ester-like connectivity within the PEG framework. Overall, it is engineered to balance solubility and controlled reactivity.

Reactivity: The maleimide group typically reacts with thiols via a Michael-type addition to form a stable thioether linkage under mildly basic aqueous conditions, often using buffered media to preserve protein-ligand integrity. The Boc-protected amine can be deprotected with standard acid-labile conditions to reveal a nucleophilic amine for coupling reactions (for example, amide bond formation). Common solvents include aqueous buffer systems with compatible co-solvents for solubility.