Patent ID: 7157574

Claim:
A process for preparing a crystalline 3-chloromethyl-3-cephem derivative, comprising a reaction step of performing a reaction of a chlorinated azetidinone derivative with an alcoholate, in a solvent containing at least one alcohol, and at a pH of 8 or less, wherein the chlorinated azetidinone derivative is expressed by Chemical Formula (1): where R 1 represents one selected from the group consisting of substituted and unsubstituted aryl groups and substituted and unsubstituted heterocyclic residues, and R 2 and R 3 each represent one selected from the group consisting of substituted and unsubstituted aromatic hydrocarbon groups, and wherein the 3-chloromethyl-3-cephem derivative is expressed by Chemical Formula (2): where R 2 and R 3 each represent one selected from the group consisting of substituted and unsubstituted aromatic hydrocarbon groups.