Z-Glu(OBut)-ONp, with the CAS number 7670-08-8, is a protected amino acid derivative. Its chemical name is N-Carbobenzoxy-L-glutamic acid γ-tert-butyl ester p-nitrophenyl ester. This compound features three key protecting groups: a benzyloxycarbonyl (Z or Cbz) group on the α-amino group, a tert-butyl (OBut) ester on the γ-carboxyl side chain of glutamic acid, and a p-nitrophenyl (ONp) active ester on the α-carboxyl group. This molecule is a specialized reagent primarily used in peptide synthesis. The p-nitrophenyl ester serves as an activated carboxyl component, facilitating efficient amide bond formation with the amino group of another amino acid or peptide fragment under mild conditions. The Z and OBut protecting groups are orthogonal and can be selectively removed (Z by hydrogenolysis, OBut by acidolysis) without affecting the other, allowing for controlled, sequential peptide chain elongation, particularly useful for incorporating glutamic acid residues with a protected side chain. As a protected and activated glutamic acid derivative, it is a fundamental building block in the synthesis of peptides and peptide-like compounds for research and pharmaceutical development. Its use is critical in constructing peptides where precise control over the glutamic acid side chain's reactivity is required.