(4-methoxyphenyl)methyl (7aR,7R)-7-{[(7Z)-2,2,5,5-tetramethyl-8-[2-({[(2-methylprop-2-yl)oxy]carbonyl}amino)-1,3-thiazol-4-yl]-4,9-dioxo-7-aza-3,6-dioxanon-7-en-9-yl]amino}-3-(hydroxymethyl)-6-oxo-2,6,7,7a-tetrahydroazeto[2,1-b][1,3]thiazine-4-carboxylate