Z-D-Glu(OtBu)-OH is a protected derivative of D-glutamic acid, serving as a key building block in peptide synthesis. The Z (benzyloxycarbonyl) group protects the α-amino group, while the tert-butyl (OtBu) ester safeguards the side chain carboxyl group. This orthogonal protection strategy enables selective activation and coupling of the free α-carboxyl group to the N-terminus of the growing peptide chain, preventing unwanted side reactions. It is widely used in both solution-phase and solid-phase peptide synthesis (SPPS) to incorporate D-glutamic acid residues with precise control over stereochemistry and sequence. After assembly, the Z group can be removed via hydrogenolysis or mild acidic conditions, and the OtBu group via stronger acid treatment, yielding the free glutamic acid side chain. This reagent is invaluable in pharmaceutical research and biotechnology for synthesizing complex peptides with therapeutic potential, such as enzyme inhibitors or hormone analogs.