4-nitrobenzyl (5R, 6R)-6-[1-methyl-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-7-oxo-3-(tetrazolo[1,5-b]pyridazin-6-ylthio)-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylate (HCID 56609997)|化工社