(S,R,S)-AHPC-PEG2-NH2 hydrochloride

Background Introduction

(S,R,S)-AHPC-PEG2-NH2 hydrochloride is a specialized E3 ligase ligand-linker conjugate widely utilized in the design and synthesis of PROTACs (Proteolysis Targeting Chimeras). Based on the AHPC (hydroxyproline-based) scaffold, this molecule incorporates a hydrophilic PEG2 spacer and a terminal amine functionality, making it ideal for conjugation to target-binding ligands. The AHPC derivative confers high affinity for the von Hippel-Lindau (VHL) E3 ubiquitin ligase, a critical component in targeted protein degradation strategies.

Mechanism

The mode of action for (S,R,S)-AHPC-PEG2-NH2 hydrochloride is centered on its application as the E3 ligase ligand portion of PROTAC molecules. When chemically linked via its terminal NH2 group to a ligand that binds a protein of interest (POI), the resulting heterobifunctional PROTAC brings the E3 ligase (VHL) into close proximity with the POI. This spatial proximity enables the transfer of ubiquitin molecules from the ligase complex to the target protein, effectively marking it for recognition and subsequent degradation by the cellular proteasome. The PEG2 linker enhances solubility and provides the necessary flexibility and distance to facilitate efficient ternary complex formation and ubiquitination.

Applications

(S,R,S)-AHPC-PEG2-NH2 hydrochloride is mainly used in the synthesis of PROTAC-based drug candidates and research tools. By serving as a core building block for linking E3 ligase ligands to protein-targeting moieties, it enables the rapid development of novel small-molecule degraders for various disease-related proteins. Common applications include studying degradation mechanisms for undruggable targets, generating potent and selective chemical probes, and creating next-generation therapeutic molecules for cancer, neurodegeneration, and other diseases leveraging targeted protein degradation. Researchers in medicinal chemistry, chemical biology, and drug discovery frequently utilize this compound for constructing custom PROTAC libraries and optimizing protein degrader activity.

The (S,R,S)-AHPC-PEG2-NH2 hydrochloride serves as an essential E3 Ligase Ligand-Linker Conjugate in the development of PROTACs, facilitating targeted protein degradation by effectively bridging the E3 ligase and target protein. The following provides a detailed description of this molecule's linker, ligand, and selection of target protein ligands.

Linker: This molecule features a PEG2 linker, which is characterized by its moderate length and flexibility, allowing for optimal spatial arrangement between the ligand and the target protein. The PEG2 linker is non-cleavable, ensuring stability throughout the degradation process.

Ligand: The ligand in this molecule is an AHPC derivative, known for its high affinity and specificity towards the E3 ligase. Structurally, it is designed to maintain robust binding while facilitating the recruitment of the ligase to the target protein.

Reactive Site: The reactive site of the (S,R,S)-AHPC-PEG2-NH2 hydrochloride is the terminal amine group. This site is suitable for coupling with target protein ligands through amide bond formation or other nucleophilic substitution reactions, ensuring efficient conjugation.

Recommended Target Protein Ligand: Compatible warheads for this molecule include electrophilic groups such as acrylamides or chloroacetamides, which can form covalent bonds with cysteine residues on target proteins. These warheads are advantageous due to their ability to ensure irreversible binding, providing a robust approach for the degradation of challenging protein targets in experimental studies.