Fmoc-PEG24-NHS ester

Fmoc-PEG24-NHS ester is a heterobifunctional PEG-based linker designed for efficient conjugation in PROTAC workflows, enabling robust attachment of targeting ligands to amine-containing partners while preserving solubility and conformational flexibility. Its NHS ester handle supports controlled acyl transfer to primary amines, and the Fmoc group provides an orthogonal protection strategy for stepwise synthesis. The subsequent points describe the linker’s structure and practical reactivity for constructing PROTACs in the laboratory.

Structure: The molecule combines an Fmoc-protected aromatic carbamate motif with a long, flexible poly(ethylene glycol) chain and a terminal N-hydroxysuccinimide ester. It contains amide and ester functionalities, aromatic rings, and ether linkages typical of PEG, conferring high aqueous compatibility and reduced nonspecific interactions.

Reactivity: The NHS ester reacts with primary amines via nucleophilic acyl substitution to form stable amide bonds, typically under mildly basic conditions that maintain amine nucleophilicity while limiting hydrolysis. Commonly used solvents include polar aprotic media or buffered aqueous-organic mixtures compatible with NHS chemistry. No specialized catalysts are required; careful control of pH, temperature, and reaction time helps maximize coupling efficiency and minimize side reactions such as hydrolysis.