Clarithromycin EP Impurity E(3R,4S,5S,6R,7R,9R,11R,12R,13R,14R)-6-(((2S,3R,4S,6R)-4-(dimethylamino)-3-hydroxy-6-methyltetrahydro-2H-pyran-2-yl)oxy)-14-ethyl-13-hydroxy-4-(((2R,4R,5S,6S)-5-hydroxy-4-methoxy-4,6-dimethyltetrahydro-2H-pyran-2-yl)oxy)-7,12-dimethoxy-3,5,7,9,11,13-hexamethyloxacyclotetradecane-2,10-dione