H-D-Phe(3-CN)-OH is primarily utilized in peptide synthesis and pharmaceutical research. It serves as a key building block in the development of peptide-based drugs, particularly in the design of enzyme inhibitors and receptor ligands. Its unique structure, featuring a cyano group, enhances binding affinity and stability, making it valuable in creating bioactive peptides. Additionally, it is employed in studies focused on understanding peptide-protein interactions and in the synthesis of modified peptides for therapeutic applications. Its role in medicinal chemistry is significant for developing treatments targeting various diseases, including cancer and metabolic disorders.