Used in solid-phase peptide synthesis as a protected peptide building block, particularly in the preparation of antibody-drug conjugates (ADCs). The Fmoc group allows for orthogonal protection during stepwise synthesis, enabling selective deprotection under mild basic conditions. The PABC (para-aminobenzyloxycarbonyl) linker serves as a self-immolative spacer, releasing the active payload upon enzymatic or chemical triggering. The PNP (p-nitrophenyl) ester acts as an activated leaving group, facilitating efficient conjugation to lysine residues on antibodies or other biomolecules. This compound is valuable in constructing prodrugs and targeted therapeutics where controlled release of a cytotoxic agent is required.