Azido-PEG5-PFP ester

Azido-PEG5-PFP ester is a bifunctional PROTAC linker designed to couple an azide-bearing handle with a highly reactive pentafluorophenyl (PFP) ester for efficient assembly of targeted protein degraders. Its PEG-based spacer provides conformational flexibility and improved solubility, while the PFP ester enables rapid formation of amide bonds under mild conditions. The azide functionality further supports downstream bioorthogonal conjugation, enabling modular PROTAC construction; detailed structural and reactivity considerations are provided below.

Structure: The linker contains a polyethylene glycol chain terminated by an azide group and a pentafluorophenyl ester. The PFP ester is an activated carboxylate featuring electron-withdrawing fluorines, while the PEG segment provides ether-rich flexibility. Overall, it is a polar, water-compatible scaffold suitable for bioconjugation workflows.

Reactivity: The PFP ester reacts with primary amines to form stable amide linkages via nucleophilic acyl substitution, typically using mild base and aqueous or mixed aqueous/organic solvents to maintain solubility. The azide group is generally preserved under these coupling conditions. For PROTAC assembly, prepare the amine-bearing partner, then combine under controlled pH; subsequent azide-specific conjugation can be performed using standard copper-free or copper-catalyzed azide–alkyne chemistries as appropriate.