E3 ligase ligand-linker conjugates 39 are primarily utilized in the field of targeted protein degradation, a cutting-edge approach in drug discovery and therapeutic development. These conjugates play a crucial role in the design of Proteolysis-Targeting Chimeras (PROTACs), which are bifunctional molecules that recruit E3 ubiquitin ligases to specific target proteins, marking them for degradation by the proteasome. This technology is particularly valuable for targeting proteins that are traditionally considered "undruggable," such as those lacking enzymatic activity or well-defined binding pockets. By enabling the selective degradation of disease-causing proteins, E3 ligase ligand-linker conjugates 39 contribute to the development of novel treatments for cancers, neurodegenerative disorders, and other conditions driven by aberrant protein function. Their application also extends to chemical biology research, where they are used to study protein function and validate therapeutic targets.