(2R)-2-[(3Z)-4-[2-({[(7aR,7R)-7-{[(3Z)-4-(2-amino-1,3-thiazol-4-yl)-5-oxo-3-aza-2-oxapent-3-en-5-yl]amino}-4-(methoxycarbonyl)-6-oxo-2,6,7,7a-tetrahydroazeto[2,1-b][1,3]thiazin-3-yl]methyl}amino)-1,3-thiazol-4-yl]-7-carboxy-5-oxo-3,6-diaza-2-oxahept-3-en-7-yl]-5-(acetoxymethyl)-2H,3H,6H-1,3-thiazine-4-carboxylic acid