Antibacterial penicillins of the formula ##STR1## or a pharmaceutically acceptable salt thereof wherein R.sup.1 is a heterocyclic group and R is hydrogen, the residue of certian carboxy protecting groups or the residue of an ester group readily hydrolyzable in vivo having activity against resistant organisms.
公式##STR1##的抗菌
青霉素或其药用盐,其中R.sup.1是一个杂环基团,R是氢,具有对抗抗药性
生物活性的某些羧基保护基团的残基或在体内容易
水解的酯基团的残基。