[2R-(2α,3β,6α)]-3-Azido-3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]octane-2-carboxylic Acid 5,5-Dioxide Diphenylmethyl Ester is an intermediate in the synthesis of Tazobactam Sodium Salt-13C2,15N1 (T010102), which is a labelled analogue of Tazobactam Sodium Salt (T010100), which is a β-Lactamase inhibitor, used with β-lactam antibiotics to enhance their effect.