Mal-PEG1-acid

Mal-PEG1-acid is a PEG-based PROTAC linker building block designed to couple protein-binding ligands through a maleimide handle and a carboxylic acid functionality. Its flexible, hydrophilic PEG segment can improve solubility and spacing between warhead and targeting moieties, supporting efficient ternary complex formation in targeted protein degradation workflows. Detailed structural and synthetic considerations are provided below.

Structure: Mal-PEG1-acid contains a maleimide electrophile for selective conjugation and a terminal carboxylic acid for subsequent coupling. The linker incorporates a short polyethylene glycol chain, providing ether-rich flexibility. It features conjugated carbonyl groups within the maleimide ring and amide/ester-forming potential at the acid terminus.

Reactivity: The maleimide group reacts with thiols via a Michael-type addition, enabling chemoselective installation of the linker onto cysteine-containing ligands or thiolated intermediates under mildly basic, aqueous-compatible conditions. The carboxylic acid can be activated for amide bond formation using standard coupling chemistries with appropriate bases and coupling reagents in polar aprotic or aqueous/organic mixtures. Typical workflows proceed by thiol–maleimide conjugation followed by acid activation/coupling to assemble PROTAC constructs.