Clarithromycin EP Impurity A 

Chemical Name: (3R,4S,5S,6R,7R,9R,11R,12R,13S,14R)-6-(((2S,3R,4S,6R)-4-(Dimethylamino)-3-hydroxy-6-methyltetrahydro-2H-pyran-2-yl)oxy)-14-ethyl-12,13-dihydroxy-4-(((2R,4R,5S,6S)-5-hydroxy-4-methoxy-4,6-dimethyltetrahydro-2H-pyran-2-yl)oxy)-3-(hydroxymethyl)-7-methoxy-5,7,9,11,13-pentamethyloxacyclotetradecane-2,10-dione

Synonym:  Clarithromycin F ; 2-Demethyl-2-(hydroxymethyl)-6-O-methylerythromycin A