p-nitrobenzyl 6-aminopenicillanate

p-Nitrobenzyl 6-Thioureidopenicillanate

p-nitrobenzyl (2R)-3-methyl-2-(4-oxo-5-tritylimino-3-thiazolidynyl)-3-butenoate

2-[(2R,3R)-2-(2,5-Dioxo-pyrrolidin-1-ylsulfanyl)-4-oxo-3-(trityl-amino)-azetidin-1-yl]-3-methyl-but-2-enoic acid 4-nitro-benzyl ester

bis(p-nitrobenzyl) 6-[N-(p-nitrobenzyloxycarbonyl)glycyl-L-α-aminopimelyl]aminopenicillanate

p-Nitrobenzyl 6-Ureidopenicillanate