Propargyl-PEG12-SH

Propargyl-PEG12-SH is a polyethylene glycol (PEG) based bifunctional linker designed for constructing PROTACs and related targeted protein degradation conjugates. It combines a terminal alkyne handle for bioorthogonal coupling with a thiol functionality that can participate in thiol-reactive conjugation strategies. The PEG segment supports solubility and flexible spacing between binding modules, which can improve effective ternary complex formation. The detailed structural and reactivity considerations are provided below.

Structure: The linker contains a PEG chain providing hydrophilic, flexible spacing, terminated by a propargyl group and a thiol. It features ether linkages along the PEG backbone, a carbon–carbon triple bond at the propargyl terminus, and a sulfur-containing thiol for conjugation.

Reactivity: The propargyl handle enables alkyne-based coupling approaches commonly used in PROTAC assembly, including copper-catalyzed azide–alkyne cycloaddition or copper-free variants with appropriate partners. The thiol can be leveraged via thiol–maleimide or thiol–activated electrophile chemistries to form stable thioether or related linkages. Typical conditions use polar organic or aqueous buffers compatible with thiol integrity, with base or catalyst selection guided by functional-group compatibility to minimize thiol oxidation.