Eisai Chemical Co., Ltd.

Homare Shinohara

Kimio Hamamura

Takeo Kanai

Akio Imai

Katsuhiko Sato

Hirofumi Kuroda

Kazumi Oishi

Masato Kodama

An industrially excellent, novel process for producing cephem compounds which are useful as medicines, particularly, antibiotics and represented by the following formula (III): ##STR1## wherein R.sup.1 means either group represented by the following formula: ##STR2## R.sup.2 denotes a carboxyl group or a carboxyl anion, and R.sup.3 stands for a lower alkyl group, a halogen atom, a lower alkyl group substituted by an aliphatic acyloxy group having 1-6 carbon atoms, or any one of the groups represented by the following formulae: ##STR3## which comprises reacting in water a 3-cephem-4-carboxylate represented by the following formula (I): ##STR4## or a salt thereof with an acid chloride represented by the formula (II), R.sup.1 COCl.

Process for producing cephem compounds in an aqueous medium

A process is provided for the preparation of an aminothiadiazolylacetyl halide derivative represented by the following formula (II): ##STR1## wherein R.sup.1 represents a lower alkyl, cycloalkyl or halogenated lower alkyl group; and R.sup.2 represents an amino-protecting group or a hydrogen atom, or a salt thereof, which process uses as the starting material a compound represented by the following formula (I): ##STR2## wherein R.sup.1 and R.sup.2 have the same meanings as defined above, or a salt thereof.

Process for the preparation of aminothiadiazolylacetyl halide derivtives

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Ibaraki, Japan

Homare Shinohara