BOC-PHE-OBZL, also known as N-(tert-Butoxycarbonyl)-L-phenylalanine benzyl ester, is a protected form of L-phenylalanine used as a building block in peptide synthesis. The Boc group protects the N-terminal amino group, preventing unwanted side reactions, while the benzyl (Bzl) ester protects the C-terminal carboxylic acid. This dual protection enables selective deprotection and stepwise coupling in solid-phase peptide synthesis (SPPS), ensuring precise control over peptide sequence and structure. The Boc group is readily removed under mild acidic conditions (e.g., TFA), and the benzyl ester can be cleaved by hydrogenation or other methods. It is widely applied in the synthesis of bioactive peptides, pharmaceuticals, and research into protein folding and enzyme mechanisms.