Propargyl-PEG9-bromide

Propargyl-PEG9-bromide is a PEG-based alkyl bromide linker designed for constructing PROTACs and related targeted protein degradation conjugates. Its ether-rich, flexible spacer supports productive ternary-complex formation by improving solubility and conformational accessibility between the ligand and the reactive handle. The terminal propargyl functionality enables orthogonal “click” conjugation strategies, while the bromide provides a defined electrophilic site for controlled attachment. Detailed structural and reactivity considerations are provided below.

Structure: Propargyl-PEG9-bromide features a poly(ethylene glycol) ether chain bearing a terminal propargyl group and a primary bromide. The molecule contains multiple ether linkages, an alkyne, and a carbon–bromine bond, yielding a polar, flexible scaffold with ether-mediated hydrogen-bonding capacity and good aqueous compatibility.

Reactivity: The bromide can participate in nucleophilic substitution with suitable nucleophiles (such as amines or thiolates) under standard alkylation conditions to install the linker onto ligand-bearing functional groups. The terminal alkyne is compatible with copper-catalyzed azide–alkyne cycloaddition for modular PROTAC assembly, typically requiring an inert or controlled atmosphere, appropriate base, and a Cu(I) source or stabilized catalyst system in compatible solvents.