methyl (2S)-2-[(4S)-4-chloro-2-oxazetidin-1-yl]-2-(1-chlorothio-1-methylethyl)-acetate

(R)-2-((R)-2-benzothiazol-2-yldisulfanyl-4-oxo-azetidin-1-yl)-3-methyl-but-3-enoic acid methyl ester

methyl penicillanate S-oxide

3(S)-bromo-4(R)-<(2,5-dihydroxyphenyl)sulfonyl>-1-<1-(methoxycarbonyl)-2-methyl-1-propen-1-yl>azetidin-2-one