[(2,2-dimethylpropanoyl)oxy]methyl (7aR,7R)-3-[(carbamoyloxidanyl)methyl]-7-{[(2Z)-2-(2-{[(2R)-2-[(2R)-5-[(carbamoyloxidanyl)methyl]-4-(6,6-dimethyl-1,5-dioxo-2,4-dioxahept-1-yl)-3H,2H,6H-1,3-thiazin-2-yl]-2-{[(2Z)-2-(2-amino-1,3-thiazol-4-yl)-1-oxopent-2-enyl]amino}acetyl]amino}-1,3-thiazol-4-yl)-1-oxopent-2-enyl]amino}-6-oxo-2,6,7,7a-tetrahydroazeto[2,1-b][1,3]thiazine-4-carboxylate