(2R,4R)-1-Benzyl 2-methyl 4-hydroxypyrrolidine-1,2-dicarboxylate, also known as N-Cbz-cis-4-hydroxy-D-proline methyl ester, is a chiral, protected hydroxyproline derivative. It features a pyrrolidine ring with a hydroxyl group at the 4-position and both a benzyloxycarbonyl (Cbz) protecting group on the nitrogen and a methyl ester on the carboxylic acid. This specific stereochemistry (2R,4R) is crucial for its applications. This compound serves as a key chiral building block in the synthesis of complex molecules, particularly in medicinal chemistry. Its primary application is as a constrained, hydroxylated proline analog for the synthesis of peptides and peptidomimetics. The cis-4-hydroxy-D-proline scaffold is a privileged structure found in various biologically active compounds and is used to introduce conformational rigidity and specific hydrogen-bonding interactions into peptide chains, which can enhance binding affinity and metabolic stability. As a protected amino acid derivative, it is a valuable intermediate in solid-phase peptide synthesis (SPPS) and solution-phase peptide chemistry. The Cbz protecting group can be selectively removed under mild hydrogenolytic conditions, allowing for further chain elongation or modification. Its utility extends to the research and development of pharmaceuticals targeting proteases, receptors, and other protein-protein interactions.