Erythromycin EP Impurity E (Erythromycin A Enol Ether)

(2R,3R,4S,5R,8R,9S,10S,11R,12R)-11-(((2S,3R,4S,6R)-4-(dimethylamino)-3-hydroxy-6-methyltetrahydro-2H-pyran-2-yl)oxy)-5-ethyl-3,4-dihydroxy-9-(((2R,4R,5S,6S)-5-hydroxy-4-methoxy-4,6-dimethyltetrahydro-2H-pyran-2-yl)oxy)-2,4,8,10,12,14-hexamethyl-6,15-dioxabicyclo[10.2.1]pentadec-1(14)-en-7-one