(4R,5S,6S)-3-[(3S,5S)-1-Allyloxycarbonyl-5-((E)-3-allyloxycarbonylamino-propenyl)-pyrrolidin-3-ylsulfanyl]-6-((R)-1-hydroxy-ethyl)-4-methyl-7-oxo-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid allyl ester