| 摘要 |
This application discloses antibacterial cephems of the formula: <IMAGE> wherein R1 represents hydrogen, alkyl, alkenyl, heterocyclylalkyl, or aralkyl; R3 is a 5- or 6-membered heterocyclic ring selected from: <IMAGE> and X is sulfur or oxygen. Included also are pharmaceutically acceptable salts and esters of such compounds; pharmaceutical compositions thereof, and methods of treatment comprising such compositions when an antibiotic effect is needed.
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