Vincristine Nitroso Impurity 17

Methyl (3aR,3a1R,4R,5S,5aR,10bR) -4-acetoxy-3a-ethyl-9- ((3R,5S,7R,9S) -5-ethyl-5-hydroxy-9- (methoxycarbonyl) -1,4,5,6,7,8,9,10-octahydro-2H-3,7-methano[1]azacycloundecino[5,4-b]indol-9-yl) -5-hydroxy-8-methoxy-5a-methyl-6-nitroso-3a,3a1,4,5,5a,6,11,12-octahydro-1H-indolizino[8,1-cd]carbazole-5-carboxylate