(R)-1-Methoxy-1-oxopent-4-yn-2-ammonium chloride is a chiral building block featuring an ammonium chloride salt, a methyl ester, and a terminal alkyne group. Its molecular formula is C6H10ClNO2. This compound is a key intermediate in the synthesis of various pharmaceutical agents, particularly those targeting the central nervous system. The primary application of this chiral intermediate is in the synthesis of (R)-(-)-Phenylephrine hydrochloride, a selective α1-adrenergic receptor agonist used as a decongestant and mydriatic agent. Its chiral center and functional groups make it a versatile precursor for constructing molecules with specific stereochemistry required for biological activity. The terminal alkyne allows for further derivatization via click chemistry or Sonogashira coupling. As a chiral synthon, it is valuable in medicinal chemistry for the development of enantiomerically pure drugs. It is typically handled under inert atmosphere and stored at low temperatures to maintain stability.