4-amino-1,2-oxazolidin-3-one organonitrogen heterocyclic antibiotic organooxygen heterocyclic antibiotic D-cycloserine Cs A 4-amino-1,2-oxazolidin-3-one that has <i>R</i> configuration. It is an antibiotic produced by <em>Streptomyces garyphalus</em> or <em>S. orchidaceus</em> and is used as part of a multi-drug regimen for the treatment of tuberculosis when resistance to, or toxicity from, primary drugs has developed. An analogue of <small>D</small>-alanine, it interferes with bacterial cell wall synthesis in the cytoplasm by competitive inhibition of <small>L</small>-alanine racemase (which forms <small>D</small>-alanine from <small>L</small>-alanine) and <small>D</small>-alanine—<small>D</small>-alanine ligase (which incorporates <small>D</small>-alanine into the pentapeptide required for peptidoglycan formation and bacterial cell wall synthesis). CHEBI:4030 CYC second line or reserve tuberculosis drug