PROCEDURE FOR THE PRODUCTION OF NEW OF PENICILLIN DERIVATIVES.
2 A class of 6-methoxy- alpha -carboxy penicillins have antibacterial activity against a wide range of Gram-negative organisms. 1. A compound of formula (I): ##STR18## where R is 2- or 3- thienyl and R.sup.1 is hydrogen or a pharmaceutically acceptable salting ion and R.sup.2 is hydrogen, or a pharmaceutically acceptable salting ion or conventional pharmaceutically acceptable hydrolysable ester radical. 2. A compound as claimed in claim 1 where R is 3-thienyl. 3. A compound as claimed in claim 1 where is 6-.beta.-(2-carboxy-2-thien-3'-ylacetamido)-6-.alpha.-methoxy penicillanic acid. 4. A compound as claimed in claim 1 which is 6-.beta.-(2-carboxy-2-thien-2'-ylacetamido)-6-.alpha.-methoxy-penicillanic acid. 5. A pharmaceutical composition having antibacterial activity comprising an antibacterially effective amount of a compound as claimed in claim 1 together with a pharmaceutical carrier or excipient. 6. A pharmaceutical composition according to claim 5 in which the compound is 6-.beta.-(2-carboxy-2-thien-3'-ylacetamido)-6-.alpha.-methoxy penicillanic acid. 7. A pharmaceutical composition according to claim 5 in which the compound is 6-.beta.-(2-carboxy-2-thien-2'-ylacetamido)-6-.alpha.-methoxy penicillanic acid.