3-​Chloromethyl oxacephem as a 5-oxa-1-azabicyclo[4.2.0]oct-2-en-8-one heterocycle displayed the potent antibacterial activity against both Gram-positive and Gram-negative bacteria. Importantly, it can be used as a starting material to synthesize Latamoxef and Flomoxef. However, the industrial route of 3-​chloromethyl oxacephem is trival and low yielding. Therefore, discovery a Simple and productive synthetic method is very necessary. The inexpensive 6-Aminopenicillanic acid was used to obtain the 3-​chloromethyl oxacephem in our group.