(2S,4R)-1-(tert-Butoxycarbonyl)-4-hydroxypyrrolidine-2-carboxylic acid, commonly known as Boc-L-hydroxyproline, is a protected derivative of the non-proteinogenic amino acid trans-4-hydroxy-L-proline. Its structure features a pyrrolidine ring with a hydroxyl group at the 4-position and a tert-butoxycarbonyl (Boc) protecting group on the nitrogen, along with a carboxylic acid at the 2-position. This compound is a key chiral building block in organic synthesis, particularly for constructing peptides and complex heterocyclic molecules. As a versatile intermediate, Boc-L-hydroxyproline is widely utilized in the pharmaceutical industry for the synthesis of bioactive compounds, including enzyme inhibitors, antiviral agents, and central nervous system drugs. Its hydroxyl group allows for further functionalization, such as oxidation to ketones or esterification, enabling the creation of diverse drug candidates. Additionally, it serves as a precursor in the preparation of proline analogs and collagen-related peptides, making it valuable in medicinal chemistry and biochemical research.