Linezolide Impurity B

Linezolid Impurity B is a structurally related oxazolidinone derivative featuring a thiazolidine ring fused to a substituted pyridine moiety, with a fluorinated benzyl group appended via an ether linkage. The compound retains the core oxazolidinone scaffold of linezolid but incorporates a methylene sulfide bridge in lieu of the parent drug’s thiazole ring, accompanied by a hydroxyl substitution at the C-3 position. This impurity arises via a side reaction during synthetic oxidation steps, leading to a stable, non-degradative byproduct. Its primary application is as an HPLC reference standard for quantifying process-related impurities in linezolid active pharmaceutical ingredient batches.