Boc-D-Asp(OtBu)-OH, with CAS number 155542-33-9, is a protected derivative of the amino acid D-aspartic acid. Its chemical structure features two orthogonal protecting groups: a tert-butoxycarbonyl (Boc) group on the α-amino function and a tert-butyl (tBu) ester on the side-chain β-carboxylic acid. This dual protection renders the molecule stable under various reaction conditions and allows for selective deprotection, making it a crucial building block in peptide synthesis, particularly for solid-phase peptide synthesis (SPPS) and solution-phase methods. This compound is primarily employed as a key intermediate in the pharmaceutical and biotechnology industries for the synthesis of peptides and peptidomimetics. The D-configuration of the aspartic acid residue is essential for creating peptides with specific biological activities, enhanced metabolic stability, or resistance to enzymatic degradation. It is extensively used in research and development of therapeutic peptides, including hormone analogs, enzyme inhibitors, and diagnostic agents. As a high-purity, specialty amino acid derivative, Boc-D-Asp(OtBu)-OH is a fundamental reagent in medicinal chemistry and life sciences. Its main utility lies in constructing peptide chains where aspartic acid needs to be incorporated in its D-form with protected side-chain functionality, preventing unwanted side reactions during coupling steps and enabling the synthesis of complex, biologically active molecules.