(2S,4S,5R)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic Acid 4-Oxide Phenylmethyl Ester-d2 is an intermediate in the synthesis of Tazobactam-d4 which is the labeled analog of Tazobactam (T010095), a β-Lactamase inhibitor, used with β-lactam antibiotics to enhance their effect.