(7aR,7R)-3-[(3Z,7R)-7-[(2R)-4-carboxy-5-(hydroxymethyl)-6H,2H,3H-1,3-thiazin-2-yl]-4-(2-furyl)-5,8-dioxo-3,6-diaza-2,9-dioxadec-3-en-10-yl]-7-{[(3Z)-4-(2-furyl)-5-oxo-3-aza-2-oxapent-3-en-5-yl]amino}-6-oxo-2,6,7,7a-tetrahydroazeto[2,1-b][1,3]thiazine-4-carboxylic acid