N-(tert-Butoxycarbonyl)-hydroxyproline (Boc-Hyp-OH), often denoted as BOC-HYP-OL, is an N-protected derivative of hydroxyproline widely used as a building block in solid-phase and solution-phase peptide synthesis. The Boc group specifically protects the α-amino group, enabling selective activation and coupling of the carboxylic acid terminus to form peptide bonds while minimizing side reactions. The side-chain hydroxyl group of hydroxyproline remains unprotected in this form, allowing it to participate in hydrogen bonding or further modification if required. This compound is crucial for synthesizing complex peptides and proteins containing hydroxyproline, such as collagen fragments, antimicrobial peptides, and glycoprotein analogs. It also plays a key role in medicinal chemistry for developing peptide-based pharmaceuticals, where precise stereochemistry and functional group orthogonality are vital for biological efficacy and stability under synthetic conditions.