Abstract: The present invention provides a process for preparing a 3-formylcephem derivative represented by the formula (2) ##STR1## which comprises oxidizing in the presence of oxygen a 3-halomethylcephem derivative represented by the formula (1) ##STR2## wherein R.sup.1 is amino group or protected amino group, R.sup.2 is hydrogen atom or a carboxylic acid protective group, X is halogen atom.

Abstract: A process for preparing a .beta.-lactam derivative of formula (2) and/or the corresponding enol tautomer, which includes oxidizing an alkenyl-substituted .beta.-lactam derivative of formula (1) in the presence of a ruthenium catalyst or a rhenium catalyst using a periodic acid: ##STR1## wherein R.sup.1 is a hydrogen atom, a C.sub.1-4 alkyl group or a C.sub.1-4 haloalkyl group, R.sup.2 is a hydrogen atom, a C.sub.1-4 alkyl group or a phenyl group which may have a substituent, A is a group selected from ##STR2## wherein R.sup.3 is an amino group or a protected amino group, and R.sup.4 -R.sup.8 are as defined in the application.

Abstract: This invention provides a method of producing a .beta.-lactam derivative represented by the formula (I): ##STR1## said method consisting essentially of the step of reacting a .beta.-lactam derivative represented by the formula (II): ##STR2## with a phenol in a reaction system which consists essentially of said .beta.-lactam derivative of formula (II) and said phenol.

Abstract: Disclosed is a method of producing a 3-exomethylenecepham of the formula ##STR1## wherein R.sup.1 is amino or substituted amino and R.sup.2 is a carboxy-protecting group comprising reacting a cephem of the formula ##STR2## wherein R.sup.1 and R.sup.2 are as defined above and X is halogen with lead metal while maintaining the pH of the reaction system at about 0.1 to 8. The cephem (I) may be reacted with a catalytic amount of lead metal or a lead compound in the presence of a metal having a greater ionization tendency than lead.

Abstract: This invention provides a process for preparing 3-exomethylenecepham derivatives represented by the formula ##STR1## wherein R.sup.1 is arylacetylamino, aryloxyacetylamino, heterocyclic acetylamino or imido, and R.sup.2 is a protective group for the carboxyl, the process being characterized in that a 3-halomethylcephem compound represented by the formula ##STR2## wherein R.sup.1 and R.sup.2 are as defined above, and X is a halogen atom is electrolyzed in a mixture of a hydrophilic organic solvent and water.

Abstract: This invention provides a process for preparing a thiosulfonate derivative represented by the formulaR.sup.2 SO.sub.2 SR.sup.1 (III)wherein R.sup.1 is substituted or unsubstituted 2-benzothiazolyl, and R.sup.2 is substituted or unsubstituted phenyl, the process being characterized in that a compound represented by the formulaR.sup.1 SX (I)wherein R.sup.1 is as defined above, and X is hydrogen, alkali metal or SR.sup.1, and a sulfinic acid or a salt thereof represented by the formulaR.sup.2 SO.sub.2 Y (II)wherein R.sup.2 is as defined above, and Y is a hydrogen atom, alkali metal atom, alkaline earth metal atom or quaternary ammonium are subjected to an electrolytic reaction in a mixture of water and an organic solvent in the presence of a halogen salt.