Erythromycin Impurity 96

(2E,4Z,8R,9S,10S,11R,14R) -11- (((2S,3R,4S,6R) -4- (dimethylamino) -3-hydroxy-6-methyltetrahydro-2H-pyran-2-yl) oxy) -5-ethyl-1-hydroxy-9- (((2R,5S) -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]pentadeca-2,4-dien-7-one