2,2-dimethylpropanoyloxymethyl (6R,7R)-7-[[(Z)-2-(2-amino-1,3-thiazol-4-yl)pent-2-enoyl]amino]-3-[[[4-[(Z)-1-[[(6R,7R)-3-(carbamoyloxymethyl)-2-(2,2-dimethylpropanoyloxymethoxycarbonyl)-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-7-yl]amino]-1-oxopent-2-en-2-yl]-1,3-thiazol-2-yl]amino]methyl]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate