benzyl 6-acetylpenicillanate

(2S,6S)-6-[Bis-(2,2,2-trichloro-ethoxy)-phosphorylamino]-6-methoxy-3,3-dimethyl-7-oxo-4-thia-1-aza-bicyclo[3.2.0]heptane-2-carboxylic acid benzyl ester

10-chloro-6β-(4-oxo-pentanoylamino)-penicillanic acid benzyl ester

(3R,9R,11R,12S)-9-Methyl-2,6-dioxo-7-oxa-10-thia-1,4-diaza-tricyclo[7.2.1.03,11]dodecane-12-carboxylic acid benzyl ester

(R)-2-[(2R,3R)-3-Allyloxycarbonylamino-2-(benzothiazol-2-yldisulfanyl)-4-oxo-azetidin-1-yl]-3-methyl-but-3-enoic acid benzyl ester