Candesartan Impurity: 1H-Benzimidazole-7-carboxylic acid, 2-ethoxy-1-[[2'-(2H-tetrazol-5-yl)[1,1'-biphenyl]-4-yl]methyl]-, (1S)-1-[[(cyclohexyloxy)carbonyl]oxy]ethyl ester(Candesartan cilexetil S-isomer).