Boc-Citrulline, with the chemical name (R)-2-((tert-Butoxycarbonyl)amino)-5-ureidopentanoic acid, is a protected derivative of the non-proteinogenic amino acid L-citrulline. It features a tert-butoxycarbonyl (Boc) group protecting the alpha-amino functionality, making it a crucial building block in solid-phase peptide synthesis (SPPS) and other peptide chemistry applications. This compound is primarily used in the research and development of peptides and peptidomimetics. Its key role is to incorporate the citrulline residue into peptide chains. Citrullination, the post-translational conversion of arginine to citrulline, is a biologically significant process, and peptides containing citrulline are of great interest in immunological studies, particularly in relation to autoimmune diseases like rheumatoid arthritis. Therefore, Boc-Citrulline serves as an essential intermediate for synthesizing such research peptides and potential therapeutic agents. As a specialty, protected amino acid, it is handled under standard laboratory conditions for moisture-sensitive reagents. It is not a commodity chemical but a high-value research chemical supplied for life science and medicinal chemistry applications.