Boc-D-3-Cyanophenylalanine is a non-natural, protected amino acid derivative. Its structure features a D-configuration phenylalanine core with a cyano substituent at the meta-position of the phenyl ring and a tert-butoxycarbonyl (Boc) group protecting the amine functionality. This combination of a chiral center, a protected amine, and a reactive nitrile group makes it a versatile building block. This compound is primarily employed as a key intermediate in the synthesis of peptides and peptidomimetics for pharmaceutical research. The D-configuration and the cyano group are often introduced to modulate the biological activity, metabolic stability, and binding affinity of the target peptide. It is particularly valuable in the development of protease inhibitors and other bioactive molecules where specific steric and electronic properties are required. The Boc protecting group allows for orthogonal deprotection strategies in solid-phase peptide synthesis (SPPS) and solution-phase chemistry. Its high purity and defined stereochemistry are critical for ensuring the quality and reproducibility of the final drug candidates in preclinical and discovery stages.