(2S,5R,6R)-2-(4-Nitrobenzyloxycarbonyl)-3,3-dimethyl-6-(phenoxyacetylamino)-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane4-oxide

(2S,5β)-3,3-Dimethyl-2β-[[(4-nitrobenzyl)oxy]carbonyl]-7-oxo-6α-[(2-phenoxyacetyl)amino]-4-thia-1-azabicyclo[3.2.0]heptane4-oxide

4-nitrobenzyl [2S-(2alpha,5alpha,6beta)]-3,3-dimethyl-7-oxo-6-(phenoxyacetamido)-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate 4-oxide