H-Phe(4-CN)-OH is primarily used in peptide synthesis, particularly in the development of bioactive peptides and peptidomimetics. Its incorporation into peptide chains can enhance binding affinity and specificity for target proteins, making it valuable in drug discovery and therapeutic applications. The cyano group on the phenyl ring allows for unique interactions, such as hydrogen bonding or dipole interactions, which can improve the stability and activity of the peptide. It is also utilized in research to study enzyme-substrate interactions and receptor-ligand binding mechanisms. Additionally, this compound serves as a building block in the synthesis of modified peptides for probing biological pathways or designing inhibitors for specific enzymes.