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(2007/10/02)(6R,7R)-7-Benzoylamino-3-hydroxy-8-oxo-5-oxa-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester
(2R,6R,7R)-7-Benzoylamino-3-methylene-8-oxo-5-oxa-1-aza-bicyclo[4.2.0]octane-2-carboxylic acid benzhydryl ester
(2R,3R,6R,7R)-7-Benzoylamino-3-hydroxy-8-oxo-5-oxa-1-aza-bicyclo[4.2.0]octane-2-carboxylic acid benzhydryl ester
(6R,7R)-7-Benzoylamino-3-chloro-8-oxo-5-oxa-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester