(R)-2-(Methoxymethyl)morpholine hydrochloride is a chiral morpholine derivative. It features a morpholine ring substituted with a methoxymethyl group at the 2-position, and it is provided as a hydrochloride salt. The compound is characterized by its (R)-configuration at the stereogenic center. This compound is primarily utilized as a key chiral intermediate in pharmaceutical synthesis. Its most notable application is in the synthesis of Gefapixant (formerly known as AF-219 or MK-7264), a P2X3 receptor antagonist developed for the treatment of refractory chronic cough. The (R)-2-(methoxymethyl)morpholine moiety serves as a crucial structural component in the Gefapixant molecule, contributing to its pharmacological activity and selectivity. As a chiral building block containing both a secondary amine and an ether functionality within a morpholine scaffold, it is also of interest in medicinal chemistry and asymmetric synthesis for constructing complex molecules. It is typically handled under standard laboratory conditions, and its hydrochloride salt form enhances stability and handling properties.