The first platinum(IV) complexes involving aromatic cytokinins or cyclin-dependent kinase inhibitors derived from 6-benzylaminopurine: X-ray structures of

Organometallic 3-(1H-benzimidazol-2-yl)-1H-pyrazolo[3,4-b]pyridines as potential anticancer agents

Six organometallic complexes of the general formula [M^IICl(η⁶-p-cymene)(L)]Cl, where M = Ru (11a, 12a, 13a) or Os (11b, 12b, 13b) and L = 3-(1H-benzimidazol-2-yl)-1H-pyrazolo[3,4-b]pyridines (L1–L3) have been synthesized. The latter are known as potential cyclin-dependent kinase (Cdk) inhibitors. All compounds have been comprehensively characterized by elemental analysis, one- and two-dimensional NMR spectroscopy, UV–vis spectroscopy, ESI mass spectrometry, and X-ray crystallography (11b and 12b). The multistep synthesis of 3-(1H-benzimidazol-2-yl)-1H-pyrazolo[3,4-b]pyridines (L1–L3), which was reported by other researchers, has been modified by us essentially (e.g., the synthesis of 5-bromo-1H-pyrazolo[3,4-b]pyridine-3-carboxylic acid (3) via 5-bromo-3-methyl-1H-pyrazolo[3,4-b]pyridine (2); the synthesis of 1-methoxymethyl-2,3-diaminobenzene (5) by avoiding the use of unstable 2,3-diaminobenzyl alcohol; and the activation of 1H-pyrazolo[3,4-b]pyridine-3-carboxylic acids (1, 3) through the use of an inexpensive coupling reagent, N,N′-carbonyldiimidazole (CDI)). Stabilization of the 7b tautomer of methoxymethyl-substituted L3 by coordination to a metal(II) center, as well as the NMR spectroscopic characterization of two tautomers 7b-L3 and 4b′-L3 in a metal-free state are described. Structure–activity relationships with regard to cytotoxicity and cell cycle effects in human cancer cells, as well as Cdk inhibitory activity, are also reported.

Three organic compounds L1−L3, known as potential Cdk inhibitors, and six novel complexes of the general formula [M^IICl(η⁶-p-cymene)(L)]Cl, where M = Ru (11a, 12a, 13a) or Os (11b, 12b, 13b) and L = L1−L3, correspondingly, have been synthesized and comprehensively characterized by elemental analysis, ESI mass-spectrometry, spectroscopic and X-ray diffraction methods. Structure−activity relationships, with regard to cytotoxicity and cell cycle effects, in human cancer cells, as well as Cdk inhibitory activity, are reported.

Platinum(II) oxalato complexes with adenine-based carrier ligands showing significant in vitro antitumor activity

[Pt(L)(2)(ox)] (1), [Pt(2-OMeL)(2)(ox)] (2), [Pt(3-OMeL)(2)(ox)] (3), [Pt(2,3-diOMeL)(2)(ox)] (4), [Pt(2,4-diOMeL)(2)(ox)] (5), [Pt(3,4-diOMeL)(2)(ox)] (6) and [Pt(3,5-diOMeL)(2)(ox)].4H(2)O (7) platinum(II) oxalato (ox) complexes were synthesized using the reaction of potassium bis(oxalato)platinate(II) dihydrate with 2-chloro-N6-(benzyl)-9-isopropyladenine or its benzyl-substituted analogues (nL). The complexes 1-7, which represent the first platinum(II) oxalato complexes involving adenine-based ligands, were fully characterized by various physical methods including multinuclear and two dimensional NMR spectroscopy. A single-crystal X-ray analysis of [Pt(2,4-diOMeL)(2)(ox)].2DMF (5.2DMF; DMF=N,N'-dimethylformamide), proved the slightly distorted square-planar geometry in the vicinity of the Pt(II) ion with one bidentate-coordinated oxalate dianion and two adenine derivatives (nL) coordinated to the Pt(II) centre through the N7 atom of an adenine moiety, thereby giving a PtN(2)O(2) donor set. In vitro cytotoxicity of the prepared complexes was tested by an MTT assay against osteosarcoma (HOS) and breast adenocarcinoma (MCF7) human cancer cell lines. The best results were achieved for the complexes 2 and 5 in the case of both cell lines, whose IC(50) values equalled 3.6+/-1.0, and 4.3+/-2.1microM (for 2), and 5.4+/-3.8, and 3.6+/-2.1microM (for 5), respectively. The IC(50) equals 9.2+/-1.5microM against MCF7 cells in the case of 1. The in vitro cytotoxicity of the mentioned complexes significantly exceeded commercially used platinum-based anticancer drugs cisplatin (34.2+/-6.4microM and 19.6+/-4.3microM) and oxaliplatin (>50.0microM for both cancer cell lines).