Synthesis, Characterization and Stat3 Inhibitory Properties of the Prototypical Platinum(IV) Anticancer Drug, [PtCl₃(NO₂)(NH₃)₂] (CPA-7)

This paper describes a reinvestigation of the literature concerning the synthesis and structural characterization of the platinum(IV)-based anticancer drug known as CPA-7 and believed to be the compound fac-[PtCl₃(NO₂)(NH₃)₂]. CPA-7 has previously been extensively investigated for its ability to control tumor cell growth by inhibition of Stat3 signaling, but very little information is available concerning its synthesis or spectroscopic properties. A reproducible synthetic route is shown to produce an active material which is characterized by IR and ¹H, ¹⁴N, ¹⁵N, and ¹⁹⁵Pt NMR spectroscopy, and single crystal X-ray crystallography. The freshly prepared drug is obtained as a single isomer which may in fact be fac- or mer-[PtCl₃(NO₂)(NH₃)₂], but recrystallization resulted in a disordered crystal containing approximately equal amounts of the two geometric isomers.