N-(Ac-PEG3)-N'-(azide-PEG3)-Cy7 chloride

N-(Ac-PEG3)-N'-(azide-PEG3)-Cy7 chloride is a multifunctional PEG-based linker reagent designed for constructing PROTACs and related targeted protein degradation probes that require orthogonal conjugation handles. Its dual PEG segments provide aqueous compatibility and flexible spacing, while the azide functionality enables bioorthogonal coupling to complementary partners. The Cy7 chloride component supports optical tracking and assay readouts, facilitating linker optimization and degradation workflow development. Detailed structural and reactivity considerations are provided below.

Structure: The molecule contains two PEG chains connected through amide-linked nitrogen centers, providing a hydrophilic, flexible scaffold. It incorporates an azide group for click-type conjugation and a Cy7 chloride chromophore for near-infrared labeling. The presence of amide, ether, and azide functionalities governs stability and solubility.

Reactivity: The azide group is suitable for copper-catalyzed azide–alkyne cycloaddition or strain-promoted azide–alkyne cycloaddition, enabling efficient attachment of PROTAC warheads or targeting ligands bearing complementary alkyne handles. Conjugations are typically performed under conditions that preserve amide integrity and maintain azide reactivity, using appropriate aqueous or mixed solvents and standard click reagents. The Cy7 chloride moiety can participate in labeling workflows where chloride-associated activation or substitution is employed, depending on the chosen coupling strategy.