Molecular and Crystal Struc

Platinum complexes of amino acids and peptides [1 – 5] have found interest as potential antitumor drugs with the idea that the coordinated bioligands might favor the transport and/or the selective uptake of the cytotoxic platinum unit into tumor cells [6 – 8]. Complexes of the type [Cl2Pt(N,Oamino acid anion)]− are formed from K2[PtCl4] and amino acids and have been reported as early as 1912 by Ley [9]. They have been characterized and used as starting compounds for other complexes by the pioneers in platinum/amino acid chemistry Volshtein and Slyudkin [1, 5, 10, 11]. Erickson and coworkers [12 – 17] could synthesize several complexes [Cl2Pt(amino acid anion)]− and have thoroughly studied their structure and chemistry by NMR spectroscopy. The complexes K[Cl2Pt(N-O)] (N-O = glycinate, alaninate) were reacted with nucleobases and nucleosides to give mixed-ligand compounds [18, 19]. Interestingly, the glycinate complex [Cl2Pt(glyO)] catalyzes the selective oxidation of sp3 carbon-hydrogen bonds in water [20]. Lippard and coworkers [21, 22] screened complexes formed in situ from K2PtCl4 and combinations of αamino acids regarding their ability to bind high mobility group protein 1 and to give DNA adducts. The lysinate complex [Cl2Pt(N,O-NH2CH(CO2)(CH2)4NH3] which was first reported by Altman et al. [23, 24] could be identified as the best candidate with moderate cytotoxicity towards tumor cells [21, 22]. The latter effect was already reported for K[Cl2Pt(N-O)] (N-O = glycinate, serinate) [25]. And recently, moderate cytotoxic effects on human tumor cells were reported for the ornithinate complex [Cl2Pt(N,ONH2CH(CO2)(CH2)3NH3], and – notably – the complex with the D-enantiomer of ornithine showed a significantly higher cytotoxicity than that with the Lisomer [26]. In the following we report on the molecular and crystal structure of K[Cl2Pt(L-alaninate)] (1). Previously, crystallographic determinations of the structures of the dichlorido complexes [Cl2Pt(N-O)] (N-O = lysinate+H+ [28], ornithinate+H+ [27]) and Cs[Cl2Pt(N-methyl-4-hydroxy-prolinate] [29] and of the chloridoplatinate(IV) complexes cis and trans-[Cl2Pt(N-O)2] (N-O = glycinate, alaninate) [30, 31], [Cl4Pt(glycinate)] [32] and [Cl3Pt(glycinate)(py)] [33] were carried out.