Used in peptide synthesis as a protected form of glutamic acid, allowing selective coupling reactions without side-chain interference. The tert-butyl (tBu) group protects the carboxylic acid side chain, enabling controlled assembly of complex peptides in solid-phase or solution-phase synthesis. Commonly applied in the production of pharmaceuticals, research peptides, and biochemical probes where precise amino acid sequencing is required. Stable under standard coupling conditions and easily deprotected under mild acidic conditions, making it ideal for stepwise peptide chain elongation.