Phenylthiohydantoin-phenylalanine is primarily utilized in the field of peptide and protein sequencing. It plays a crucial role in the Edman degradation process, a method used to determine the amino acid sequence of peptides. By selectively cleaving the N-terminal amino acid from a peptide chain, it allows for the step-by-step identification of each amino acid, aiding in the analysis of protein structures. This compound is particularly valuable in biochemical research, where understanding protein composition and function is essential. Additionally, it finds applications in proteomics and the development of pharmaceuticals, where precise protein sequencing is critical for drug design and therapeutic studies.