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(2007/10/02)trans-3-amino-4-ethoxycarbonylmethyl-2-azetidinone
trans-3-benzyloxycarbonylamino-4-ethoxycarbonylmethyl-2-azetidinone
sulfur trioxide pyridine complex
trans-3-<2-(2-tritylaminothiazol-4-yl)-2-((Z)-methoxyimino)acetamido>-4-ethoxycarbonylmethyl-2-azetidinone