(R)-3-Methyl-2-((1S,5R)-7-oxo-3-phenyl-4-oxa-2,6-diaza-bicyclo[3.2.0]hept-2-en-6-yl)-but-3-enoic acid benzhydryl ester
epi-Secopenicillin
(R)-3-Hydroxymethyl-2-((1R,5S)-7-oxo-3-phenyl-4-oxa-2,6-diaza-bicyclo[3.2.0]hept-2-en-6-yl)-but-3-enoic acid benzhydryl ester
Diphenylmethyl-2-(3R,4R-3-benzamido-4-chlor-2-oxo-azetidin-1-yl)-3-chlormethyl-3-butenoat
(R)-3-Nitrooxymethyl-2-((1R,5S)-7-oxo-3-phenyl-4-oxa-2,6-diaza-bicyclo[3.2.0]hept-2-en-6-yl)-but-3-enoic acid benzhydryl ester