p-nitrobenzyl (3R,5R)-1-carba-2-oxopenam-3-carboxylate

(R)-4-3'-diazo-3'-p-nitrobenzyloxycarbonyl-2'-oxopropyl-2-azetidinone

(S)-N-benzyl-4-carboxymethyl-2-azetidinone

(R)-3-Benzylamino-4-chlorocarbonyl-butyric acid methyl ester; hydrochloride