Boc-C1-PEG3-C4-OH

Boc-C1-PEG3-C4-OH, is designed to provide a flexible polyethylene glycol–containing spacer that can improve effective proximity between a target-binding ligand and an E3 ligase recruiter. Its protected functional group strategy supports modular synthesis, while the terminal hydroxyl enables reliable conjugation handles for assembling degraders. The following sections describe the linker’s structural features and practical reactivity considerations for PROTAC construction.

Structure: The molecule contains a Boc-protected amine segment linked to a short PEG-based chain, terminating in a hydroxyl functionality. It features carbamate and ether linkages, with multiple heteroatoms that confer polarity, hydrogen-bonding capacity, and conformational flexibility typical of PEG spacers used in bifunctional degraders.

Reactivity: The terminal hydroxyl supports standard PROTAC assembly via activation to form electrophiles for nucleophilic substitution or coupling to complementary functional groups on ligands. The Boc group enables orthogonal protection during stepwise synthesis and can be removed under acid-mediated conditions to reveal an amine for further coupling. Common approaches include carbamate/amide-forming reactions using activated carboxylic acids or halide/ester intermediates in polar organic solvents with base or coupling reagents.