[(2,2-Dimethylpropanoyl)oxy]methyl (4R,5S,6S)-6-[(1R)-1-hydroxyet hyl]-4-methyl-7-oxo-3-{[(3R)-5-oxo-3-pyrrolidinyl]sulfanyl}-1-aza bicyclo[3.2.0]hept-2-ene-2-carboxylate

phenoxymethyl 2,2-dimethylpropanoate