(4R,5S,6S)-3-((6S,7aS)-3,3-Dimethyl-1-oxo-hexahydro-pyrrolo[1,2-c]imidazol-6-ylsulfanyl)-6-((R)-1-hydroxy-ethyl)-4-methyl-7-oxo-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid