Etoposide Impurity 37

(5aS,8aR,9S) -9- (((2R,4aR,6R,7R,8R,8aS) -7,8-dihydroxy-2-methylhexahydropyrano[3,2-d][1,3]dioxin-6-yl) oxy) -5- (3,5-dimethoxy-4-oxocyclohexa-2,5-dien-1-ylidene) -5,8,8a,9-tetrahydrofuro[3',4':6,7]naphtho[2,3-d][1,3]dioxol-6 (5aH) -one