This protected dipeptide, Fmoc-Glu(OtBu)-Gly-OH, is widely used in solid-phase peptide synthesis (SPPS) as a building block to incorporate the glutamic acid-glycine sequence with orthogonal protections. The fluorenylmethyloxycarbonyl (Fmoc) group temporarily protects the N-terminal amine of glutamic acid, enabling stepwise chain assembly under mild basic deprotection conditions (e.g., piperidine in DMF). The tert-butyl (OtBu) ester safeguards the glutamic acid side chain carboxylic acid, which can be selectively deprotected post-synthesis using acidic conditions without impacting the Fmoc group or peptide backbone. The C-terminal glycine carboxylic acid remains free for coupling to the growing peptide chain on resin. This design ensures high selectivity, minimal side reactions, and efficient synthesis of complex peptides, including therapeutic agents, diagnostics, and biochemical tools. It is particularly valued in automated synthesizers for its compatibility and high purity yields.