(S)-(+)-1-Fmoc-3-hydroxypyrrolidine is a chiral pyrrolidine derivative featuring a 9-fluorenylmethoxycarbonyl (Fmoc) protecting group on the nitrogen atom and a hydroxyl group at the 3-position. It is a white to off-white crystalline powder with a molecular formula of C19H19NO3 and a molecular weight of 309.36 g/mol. The compound is characterized by its high optical purity, typically >99% ee, making it a valuable chiral building block. This compound is primarily used as a key intermediate in the synthesis of pharmaceutical agents, particularly in the development of peptidomimetics and protease inhibitors. The Fmoc group is a standard protecting group in solid-phase peptide synthesis (SPPS), allowing for the controlled assembly of peptide chains. The chiral 3-hydroxypyrrolidine scaffold is a privileged structure found in numerous bioactive molecules targeting various diseases. Its main application lies in medicinal chemistry research and the production of active pharmaceutical ingredients (APIs). As a versatile synthon, it serves as a precursor for further functionalization. The hydroxyl group can be modified through standard reactions such as oxidation, esterification, or etherification, while the Fmoc group can be selectively removed under mild basic conditions (e.g., piperidine). It is commonly supplied for research and development purposes and requires storage in a cool, dry place, protected from light.