(2(R)-2-[(Z)-2-(2-Aminothiazol-4-yl)-2-(hydroxyimino)acetamido]-2-[(2RS,5RS)-5-methyl-7-oxo-2,4,5,7-tetrahydro-1H-furo[3,4-d][1,3]thiazin-2-yl]acetic Acid is in impurity in the synthesis of Cefdinir (C242670), a Cephalosporin antibiotic structurally similar to Cefixime (C242800).