Boc-His(Trt)-Aib-Gly-OH is a protected tripeptide used in peptide synthesis. The Boc (tert-Butoxycarbonyl) group protects the N-terminus of the histidine (His) residue, preventing it from reacting during synthesis. The imidazole side chain of histidine is protected by a Trt (Trityl) group, which shields it from unwanted reactions until deprotection is performed. Aib (α-aminoisobutyric acid), known for its helical structure-inducing properties, is the middle residue. Gly (Glycine), the final amino acid, has a free carboxyl group at the C-terminus, indicated by -OH, allowing for further peptide coupling or modifications. This peptide is used to introduce histidine, Aib, and glycine into peptide sequences, with specific protections to ensure controlled and efficient peptide synthesis.