t-Boc-N-amido-PEG4-alcohol

t-Boc-N-amido-PEG4-alcohol, is designed to provide a flexible, hydrophilic polyethylene glycol spacer that can be functionalized for controlled conjugation between a targeting ligand and an E3 ligase-binding moiety. Its amphiphilic character and protected amide functionality support robust synthetic assembly and improved solubility of intermediate and final conjugates. The following sections describe the linker’s structural features and the practical reactivity considerations used in PROTAC construction.

Structure: The linker contains a polyethylene glycol chain terminated by a primary alcohol and an N-amide functionality capped with a tert-butoxycarbonyl protecting group. It features ether linkages along the PEG backbone, an amide carbonyl, and a protected nitrogen, providing conformational flexibility and enhanced aqueous compatibility.

Reactivity: The primary alcohol enables ester or ether formation via standard coupling chemistries, while the Boc-protected amide nitrogen can be deprotected under acid to reveal a reactive amine for subsequent amide bond formation. Linker assembly commonly proceeds through nucleophilic substitution or acylation steps, using coupling reagents and base in compatible organic solvents; careful control of protecting-group stability and moisture sensitivity is recommended to maintain chemoselectivity during PROTAC synthesis.