Azithromycin Impurity 59

(3R,4R,5S,6R,9R,10S,11S,12R,13S,15R, Z) -12- (((3R,4S,6R) -4- (dimethylamino) -3-hydroxy-6-methyltetrahydro-2H-pyran-2-yl) oxy) -6-ethyl-4,5-dihydroxy-10- (((2R,4R,5S,6S) -5-hydroxy-4-methoxy-4,6-dimethyltetrahydro-2H-pyran-2-yl) oxy) -3,5,9,11,13,15-hexamethyl-7,16-dioxa-2-azabicyclo[11.2.1]hexadec-1-en-8-one