(S)-1-Boc-3-cyanopyrrolidine is a chiral, non-racemic heterocyclic building block featuring a pyrrolidine ring substituted with a cyano group at the 3-position and a tert-butoxycarbonyl (Boc) protecting group on the nitrogen. It is a white to off-white crystalline powder with a molecular formula of C10H16N2O2. This compound is a key chiral intermediate in pharmaceutical synthesis. Its primary application is in the preparation of active pharmaceutical ingredients (APIs) and advanced drug candidates. The cyano group serves as a versatile handle for further chemical transformations, such as reduction to an aminomethyl group or conversion to other functional groups like tetrazoles. The Boc-protected, chiral pyrrolidine scaffold is a privileged structure found in numerous bioactive molecules, particularly those targeting the central nervous system (CNS). It is notably used in the synthesis of potent and selective inhibitors, such as dipeptidyl peptidase-4 (DPP-4) inhibitors for type 2 diabetes treatment and other enzyme targets. As a high-purity chiral synthon, it enables the efficient construction of complex molecular architectures with defined stereochemistry. It is commercially available from major fine chemical suppliers for research and development purposes. Standard safety precautions for handling laboratory chemicals should be observed.