Azithromycin Impurity R

(1S,2R,3R,6R,7S,8S,9R,10R,12R,15R)-9-(((2S,3R,4S,6R)-4-(dimethylamino)-3-hydroxy-6-methyltetrahydro-2H-pyran-2-yl)oxy)-3-ethyl-2,10-dihydroxy-7-(((2R,4R,5S,6S)-5-hydroxy-4-methoxy-4,6-dimethyltetrahydro-2H-pyran-2-yl)oxy)-2,6,8,10,12,15-hexamethyl-4,16-dioxa-14-azabicyclo[11.2.1]hexadec-13-en-5-one; 
Erythromycin A 9,11-Imino Ether