2-oxo-bisnorpenicillin G-3-benzhydryl carboxylate

(6R)-phenylacetamido-2-benzoyloxy-(5R)-penem-3-t-butyl-carboxylate

(1E,5R)-3-Phenylmethyl-4-thia-2,6-diazabicyclo[3.2.0]hept-2-en-7-one

(6R)-phenylacetamido-2-methoxy-(5R)-penem-3-t-butyl-carboxylate

2-<3-benzyl-6-oxo-2-thia-4,7-diaza-(1R,5R)-bicyclo-<3,2,0>-hept-3-en-7-yl>-allyl acetate