title: Coordination modes vs. antitumor activity: synthesis and antitumor activity of novel platinum(II) complexes of N-substituted amino dicarboxylic acids.
abstract: The trans-(+/-)-1,2-diaminocyclohexaneplatinum(II) complexes of multidentate L-glutamate (Glu) and L-aspartate (Asp) were prepared and their antitumor activity was examined in relation with their coordination modes. All these complexes were obtained as a mixture of (O,O')- and (O,N)-chelate isomers due to rapid isomerization of the initially formed (O,O')-isomer to the thermodynamically more stable (O,N)-isomer. The (O,O')/(O,N)-isomeric mixture with the mole ratio of 80/20 exhibited excellent antitumor activity while the pure (O,N)-isomer was only marginally active. Therefore, in order to prevent the linkage isomerization of the active (O,O')-isomer to the inactive (O,N)-isomer, we have designed N-substituted amino dicarboxylic acids as a leaving group and prepared a new series of complexes, [Pt(dach)(RGlu)] and [Pt(dach)(RAsp)] (dach=trans-(+/-)-1,2-diaminocyclohexane; R=acetyl (Ac), propionyl (Pro), pivaloyl (Piv), carbobenzyloxy (Cbz) or phthaloyl (Phth)) and characterized by means of elemental analyses, and 1H NMR, 195Pt NMR and IR spectroscopies. The N-substituted amino dicarboxylate ligands were found to coordinate to platinum(II) ion through only the (O,O')-chelation mode, and their Pt(II) complexes were chemically stable in aqueous solution. The present Pt(II) complexes of N-substituted amino dicarboxylic acids showed excellent antitumor activity against both murine leukemia L1210 and human tumor cells. Especially, the highly hydrophobic N-phthaloylglutamate complex, [Pt(dach)(PhthGlu)], exhibited an outstanding in vitro activity (IC50=2.22 microM) on the human stomach cancer cells which are not responsive to cisplatin and carboplatin.
authors.affiliation: Department of Chemistry, Ewha Womans University, Seoul 120-750, Republic of Korea.
authors.forename: Yeong-Sang
authors.initials: YS
authors.lastname: Kim
authors.forename: Rita
authors.initials: R
authors.lastname: Song
authors.forename: Hyun Cheol
authors.initials: HC
authors.lastname: Chung
authors.forename: Moo Jin
authors.initials: MJ
authors.lastname: Jun
authors.forename: Youn Soo
authors.initials: YS
authors.lastname: Sohn
mesh_terms: D000600:Amino Acids, Dicarboxylic / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D020128:Inhibitory Concentration 50; D007536:Isomerism; D007939:Leukemia L1210 / Q000188:drug therapy; D009944:Organoplatinum Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D000600:Amino Acids, Dicarboxylic; D000970:Antineoplastic Agents; D009944:Organoplatinum Compounds