(6R,7R)-7-Allyloxycarbonylamino-3-hydroxymethyl-8-oxo-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid

(6R,7R)-7-Allyloxycarbonylamino-8-oxo-3-(1,2,2,2-tetrachloro-ethoxycarbonyloxymethyl)-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester