(S)-Octahydropyrazino[2,1-c]-[1,4]oxazine dihydrochloride is a chiral, bicyclic heterocyclic compound containing both piperazine and morpholine-like structural motifs. It serves as a key synthetic intermediate in the development of novel antibacterial agents, particularly within the oxazolidinone class of antibiotics. This compound is a crucial building block for the synthesis of advanced oxazolidinone derivatives, such as contezolid (MRX-I) and contezolid acefosamil (MRX-4). These next-generation antibiotics are designed to combat serious Gram-positive bacterial infections, including those caused by methicillin-resistant *Staphylococcus aureus* (MRSA) and vancomycin-resistant enterococci (VRE), while aiming to improve upon the safety profile of earlier drugs like linezolid. The (S)-enantiomer is specifically required for constructing the pharmacologically active core of these drugs. Its synthesis and availability are therefore of significant importance in pharmaceutical research and development focused on addressing the global challenge of antimicrobial resistance.