OtBu-L-Glutamic acid methyl ester hydrochloride is a protected derivative of the amino acid L-glutamic acid. It features a tert-butyl ester group protecting the side-chain carboxylic acid and a methyl ester protecting the alpha-carboxylic acid, with the alpha-amino group present as its hydrochloride salt. This specific protection pattern makes it a versatile chiral building block. This compound is primarily employed as a key intermediate in the synthesis of peptides and peptidomimetics, particularly in solid-phase peptide synthesis (SPPS) and solution-phase methodologies. Its protected form allows for selective deprotection and further coupling reactions, facilitating the construction of complex peptide sequences. It is also used in the research and development of various bioactive molecules and pharmaceutical agents. As a derivative of L-glutamic acid, a fundamental proteinogenic amino acid and a major excitatory neurotransmitter, this building block finds applications in neuroscience research and the development of compounds targeting glutamate receptors. It is a standard reagent for introducing the glutamic acid residue in a controlled manner during chemical synthesis.