(5R,5aR,8aR,9S)-9-(((2R,4aR,6R,7R,8R,8aS)-7,8-dihydroxy-2-methylhexahydropyrano[3,2-d][1,3]dioxin-6-yl)oxy)-5-(4-hydroxy-3-methoxy-13cd3,5-methoxyphenyl)-5,5a,8a,9-tetrahydrofuro[3',4':6,7]naphtho[2,3-d][1,3]dioxol-6(8H)-one,Etoposide Stable Isotopes