H-D-Glu(OMe)-OtBu·HCl is the hydrochloride salt of D-glutamic acid with a free α-amino group, α-carboxylic acid as methyl ester, and γ-carboxylic acid (side chain) as tert-butyl ester. It serves as a protected amino acid derivative in peptide synthesis, primarily in solution-phase methods, where the free amino group facilitates coupling to the activated carboxyl of another residue. The differential ester protecting groups enable selective deprotection: the tert-butyl ester is removed under mild acidic conditions (e.g., TFA), while the methyl ester is stable to acid but can be hydrolyzed under basic conditions. This orthogonality minimizes side reactions and supports the construction of complex peptides incorporating D-glutamic acid with precise control over stereochemistry and side-chain protection. Widely used in pharmaceutical research for developing peptide-based drugs and in biochemical studies. The HCl salt form enhances solubility, stability, and ease of handling during storage and use.