O-Ethyl-N-[(9H-fluoren-9-ylmethoxy)carbonyl]-D-tyrosine, with CAS number 162502-65-0, is a protected derivative of the non-natural amino acid D-tyrosine. Its structure features an O-ethyl ether protecting group on the phenolic hydroxyl of tyrosine and an N-terminal Fmoc (9-fluorenylmethoxycarbonyl) protecting group. The compound is specifically in the D-configuration, distinguishing it from the more common L-tyrosine found in natural proteins. This compound is a specialized, high-purity building block primarily used in solid-phase peptide synthesis (SPPS). The Fmoc group is the standard protecting group for the α-amino function in Fmoc-based SPPS strategies, allowing for orthogonal deprotection under mild basic conditions. The O-ethyl protection on the tyrosine side chain prevents unwanted side reactions during the peptide assembly process. Its primary application is in the research and development of synthetic peptides containing D-amino acids, which are of significant interest in pharmaceutical research due to their enhanced metabolic stability and potential for novel bioactivities, such as in antimicrobial peptides or peptide-based therapeutics. As a non-natural amino acid derivative, it serves as a crucial intermediate for constructing peptides with specific stereochemistry and modified properties. It is typically handled and supplied as a fine chemical for research purposes under controlled conditions.