Improvement of the synthesis of diphenylmethyl 7beta-(o-hydroxy)benzylideneamino-3-hydroxymethyl-3-cephem-4-carboxylate.

The title product (I) is synthesized currently from 7-aminocephalosporanic acid, and diphenyldiazomethane (DDM) is used as a protective reagent of the acid function for further reactions. When DDM was prepared from benzophenone hydrazone by reaction with chloramine T, it was resulted impure by p-toluenesulfonamide, formed as side product, which cannot be removed during the final purification step carried out according to the literature procedure. Two simple methods are proposed here to obtain I with the suitable degree of purity necessary for a drug.