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