Beecham Group Plc

Pamela Brown Nee Davis

Roger J Ponsford

David F Corbett

A process for the preparation of an antibacterially active compound of the formula (I): ##STR1## and salts and esters thereof wherein R.sup.1 and R.sup.2 independently are hydrogen or an organic group, and R.sup.3 is an organic group bonded via a carbon atom to the sulphur atom, which comprises reacting a compound of the formula (II): ##STR2## wherein R.sup.4 is an organic group different to R.sup.3 and R.sup.a is hydrogen or a carboxy-blocking group, with a thiol R.sup.3 SH or reactive derivative thereof. In addition certain compounds within the formula (II) are novel and useful antibacterial agents in their own right.

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Guildford, United Kingdom

Pamela Brown Nee Davis