Glaxo Laboratories Limited

Gordan Ian Gregory

Martin Christopher Cook

Janice Bradshaw

The invention provides novel antibiotic compounds which are 7.beta.-acylamidoceph-3-em-4-carboxylic acids, and non-toxic derivatives thereof characterized in that the acylamido group has the structure ##STR1## where R is a hydrogen atom or an organic group and R.sup.a is an etherifying monovalent organic group linked to the oxygen atom through a carbon atom. The compounds are syn isomers or exist as mixtures containing at least 75% of the syn isomer. These antibiotic compounds possess high antibacterial activity against a range of gram positive and gram negative organisms coupled with particularly high stability to .beta.-lactamases produced by various gram negative organisms. The invention is also concerned with the administration of the compounds.

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Chalfont St. Peter, United Kingdom

Gordan Ian Gregory