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(1974)3-methyl-2-(3-oxo-4-phthalimido-3H-isothiazol-2-yl)-but-2-enoic acid 4-nitro-benzyl ester
1α-oxo-6β-phthalimido-1λ4-penicillanic acid 4-nitro-benzyl ester
10-bromo-6β-phthalimido-penicillanic acid 4-nitro-benzyl ester
9-bromo-6β-phthalimido-penicillanic acid 4-nitro-benzyl ester
(6R)-3-methyl-8-oxo-7t-phthalimido-(6rH)-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid 4-nitro-benzyl ester