biapenem
5H-Pyrazolo(1,2-a)(1,2,4)triazol-4-ium, 6-((2-carboxy-6-(1-hydroxyethyl)-4-methyl-7-oxo-1-azabicyclo(3.2.0)hept-2-en-3-yl)thio)-6,7-dihydro-, hydroxide, inner salt, (4R-(4alpha,5beta,6beta(R*)))-