Process for preparing 2-isocephem derivatives

Abstract

A process for preparing a 2-isocephem derivative characterized in that a thioacetic acid derivative which itself is basic or a mixture of a base and a thioacetic acid derivative is caused to act on a 2-azetidinyl-3,4-dihalogeno-2-butenoic acid compound represented by the general formula (1) in a water-containing organic solvent to obtain a 3-halomethyl-2-isocephem derivative represented by the general formula (2), and a process for preparing a 2-oxaisocephem derivative characterized in that a base is caused to act on a 2-azetidinyl-3,4-dihalogeno-2-butenoic acid compound represented by the general formula (1) in a water-containing organic solvent to obtain a 3-halomethyl-2-oxaisocephem derivative represented by the general formula (3) ##STR1## wherein R.sup.1 is a hydrogen atom, amino or protected amino, R.sup.2 is a hydrogen atom or lower alkoxyl, R.sup.1 and R.sup.2, when taken together, form a cyclic amino protecting group, R.sup.3 is a hydrogen atom or carboxylic acid protecting group, W is a leaving group, and X and Y are the same or different and are each a halogen atom ##STR2## wherein R.sup.1, R.sup.2, R.sup.3 and X are the same as above, ##STR3## wherein R.sup.1, R.sup.2, R.sup.3 and X are the same as above.

Dependencies are inferred from the claim text.