FmocNH-PEG3-CH2CH2NH2

This FmocNH-PEG3-CH2CH2NH2 linker is a polyethylene glycol–based, amine-terminated building block designed for assembling PROTACs with improved solubility and conformational flexibility. Its Fmoc-protected amine enables controlled stepwise synthesis, while the PEG spacer supports productive linker geometry between the target-binding ligand and the E3 ligase-recruiting moiety. The subsequent points describe its structure and practical reactivity for PROTAC construction in detail below.

Structure: The linker comprises an Fmoc-protected amine connected to a short PEG spacer and a terminal primary amine. It contains aromatic carbamate functionality from the Fmoc group, ether linkages within the PEG chain, and flexible aliphatic C–C and C–N bonds, yielding a polar, water-compatible scaffold.

Reactivity: Suitable PROTAC assembly typically uses the terminal primary amine for amide or urea formation with activated carboxylic acid derivatives, such as NHS esters or acid chlorides, under standard coupling conditions. The Fmoc group is removed using base to reveal the reactive amine for subsequent conjugation. Solvent systems commonly include polar aprotic media for coupling and base-compatible conditions for deprotection, with reaction progress monitored by conventional analytical methods.