title: A new class of penems, the 2-heterocyclyl(thio)methyl derivatives.
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis*; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects; D006571:Heterocyclic Compounds / Q000138:chemical synthesis / Q000633:toxicity; D008826:Microbial Sensitivity Tests; D013329:Structure-Activity Relationship; D013440:Sulfides / Q000138:chemical synthesis / Q000633:toxicity
chemical_list: D000900:Anti-Bacterial Agents; D006571:Heterocyclic Compounds; D013440:Sulfides