(R)-3-Methylmorpholine is a chiral, saturated heterocyclic compound featuring a morpholine ring with a methyl substituent at the 3-position. It is a versatile chiral building block and a key intermediate in organic synthesis, particularly valued for its role in pharmaceutical manufacturing. Its primary and most significant application is as a crucial chiral intermediate in the synthesis of various active pharmaceutical ingredients (APIs). It is notably employed in the production of Gefapixant (MK-7264), a P2X3 receptor antagonist developed for the treatment of refractory chronic cough. The stereochemistry of the (R)-enantiomer is essential for the biological activity of the final drug molecule. Beyond this specific application, it serves as a chiral amine synthon and ligand precursor in asymmetric synthesis. As a liquid with basic properties, it functions as a solvent and catalyst in certain organic reactions. Handling requires standard precautions for amines, including use in well-ventilated areas and avoidance of contact with skin and eyes.