(2R)-2-[(4S)-1-[(7aR,7S)-7-({2-[(cyanomethyl)sulfanyl]acetyl}amino)-7-methoxy-3-{[(1-methyl-1,2,3,4-tetraazol-5-yl)sulfanyl]methyl}-6-oxo-2,6,7,7a-tetrahydroazeto[2,1-b][1,3]thiazin-4-yl]-4-methoxy-1,3,6-trioxo-6-(thioformyl)-5-aza-2-oxahex-4-yl]-5-[(4-methyl-5-thioxo-1,2,3,4-tetraazol-1-yl)methyl]-2H,3H,6H-1,3-thiazine-4-carboxylic acid