(2R,5R,Z)-Benzyl 3-(2-Hydroxyethylidene)-7-oxo-4-oxa-1-azabicyclo[3.2.0]heptane-2-carboxylate is an intermediate in the synthesis of Clavulanic Acid Potassium Salt-d4 which is the isotope labelled analog of Clavulanic Acid Potassium Salt (C563750); a β-lactamase inhibitor, typically added to amoxicillin to increase its effectiveness.