BOC-PHG-OSU, the N-hydroxysuccinimide ester of N-(tert-butoxycarbonyl)-L-phenylglycine, is widely used in peptide synthesis to introduce the Boc-protected phenylglycine residue. The Boc group selectively protects the amino function during amide bond formation, while the active OSu ester enables efficient coupling to the growing peptide chain, ensuring high yields and minimal side reactions. This is particularly valuable in solid-phase peptide synthesis for stepwise assembly of peptides. It also facilitates purification by preventing unwanted reactions and is essential for preparing peptide derivatives in biochemical and pharmaceutical research to study structure-function relationships. Its stability across various conditions makes it a key reagent in organic synthesis.