(2S,3R)-Methyl 3-hydroxypyrrolidine-2-carboxylate hydrochloride is a chiral, non-proteinogenic amino acid derivative. It features a pyrrolidine ring substituted with a methyl ester at the 2-position and a hydroxyl group at the 3-position, with defined (2S,3R) stereochemistry. This compound is typically supplied as a hydrochloride salt to enhance its stability and handling properties. This compound serves as a crucial chiral building block in pharmaceutical synthesis. Its primary application is as a key intermediate in the production of various active pharmaceutical ingredients (APIs), particularly those targeting the central nervous system (CNS). For instance, it is a vital precursor in the synthesis of preclamol, a dopamine receptor agonist, and other structurally related therapeutic agents. The defined stereochemistry of the hydroxyl and ester groups is essential for imparting the desired biological activity and selectivity in the final drug molecules. As a protected form of 3-hydroxyproline, it belongs to the class of unnatural amino acids and is widely used in medicinal chemistry to introduce conformational constraints into peptide mimetics and small molecule drug candidates. Its synthesis and availability are of significant interest in process chemistry for the development of enantioselective routes to important pharmaceuticals.