Milbemycin EP Impurity I

Chemical Name: (2aE,2′R,2a1S,4E,5′S,6R,6′R,8E,11R,15S,17aR,20aR)-6′-ethyl-2a1,20a-dihydroxy-5′,6,8,19-tetramethyl-2a1,3′,4′,5′,6,6′,7,10,11,14,15,17a,20,20a-tetradecahydrospiro[2H,17H-11,15-methanofuro[4,3,2-pq][2,6]benzodioxacyclooctadecine-13,2′-pyran]-17,20-dione (20a-hydroxy-20-oxomilbemycin A4).