Novel reactions of hydroxo-bridged dinuclear platinum complexes with antitumor activity

顺铂是最有效的抗肿瘤药物之一。为了寻找更有活性的金属药物和克服顺铂耐药性，我们开发了一种双核铂配合物[{顺-铂（NH_3）_2}_2（μ-吡唑啉）μ-羟基]]^<2+> (AMPZ)及其吡唑酸类似物衍生物。它们对顺铂耐药细胞系有效。为了研究双核配合物的抗肿瘤活性与化学特性之间的关系，本项目研究了以下三个新的反应：(1)质子辅助取代反应，(2)与DNA的非共价相互作用，(3)1,2,3-三唑桥接双核铂（II）配合物与9-乙基鸟嘌呤相互作用时，铂原子从N2向N3的异构化。各反应研究结果如下：1采用高效液相色谱（HPLC）、核磁共振（1H-NMR）和电子能谱等方法研究了氯离子作为亲核试剂存在下双核铂（II）配合物的取代反应。在0.2 mol/l氯化钠溶液中，双核铂（II）配合物在中性pH区60 min内未发生反应，在高氯酸的作用下反应生成[{顺式铂（NH_3）_2}_2（μ-吡唑啉）（μ-Cl）]^<2+>作为中间体之一和[{顺式铂（NH_3）_2 Cl}_2（μ-吡唑啉）]^<2+>作为终产物。提出了配合物之间的总平衡反应在pH为7的条件下，AMPZ与5′-GMP反应生成带Pt-N7键的AMPZ-(GMP)_2，反应非常缓慢。例如，在磷酸盐缓冲液（1 × 10^<-3> mol/l， pH为7）中，AMPZ （1 × 10^<-3> mol/l）与5′-GMP （4 × 10^<-3> mol/l）在330K下反应约24小时完成反应。另一方面，加入AMPZ后，DNA的CD谱在pH为7时发生了变化，而加入氯化钠后，DNA的CD谱得到了完整的变化。平衡透析法的结合研究表明，加入氯化钠后，与DNA结合的AMPZ被去除。这两个实验表明，AMPZ可以以非共价方式结合DNA采用核磁共振波谱法对异构化反应进行了研究。当三唑啉桥接配合物与9-乙基鸟嘌呤反应时，最初与N2结合的Pt原子在与9-乙基鸟嘌呤-的N7位点反应后迁移到三唑啉环上的N3。在这三种新反应中，与DNA的非共价相互作用是最有趣的，因为最近已经报道了几种抗肿瘤金属配合物。与DNA的非共价相互作用与抗肿瘤活性的关系有待进一步研究。少

Cisplatin is one of the most effective antitumor agents. In an attempt to search for more active metallopharmaceuticals and to overcome cisplatin resistance, we have developed a dinuclear platinum complex, [{cis-Pt(NH_3)_2}_2(μ-pyrazolato)μ-hydroxo]]^<2+> (AMPZ) and its derivatives with pyrazolate analogs. They were effective against cisplatin resistant cell lines. In order to study the relationship between the antitumor activity and the chemical characteristics of the dinuclear complexes, the following three novel reactions were investigated in this project : (1) Proton-assisted substitution reaction, (2) Non-covalent interaction with DNA, and (3) Isomerization, that is, Pt atom migration from N2 to N3, on interaction of 1,2,3-triazole-bridged dinuclear platinum(II) complexes with 9-ethylguanine. The result of each reaction study is as follows.1 The substitution reaction of the dinuclear platinum(II) complex was investigated in the presence of chloride as a nucleophile by HPLC, 1H-NMR … More and electronic spectral methods. In 0.2 mol/l sodium chloride the dinuclear platinum(II) complex did not react at neutral pH region within 60 min, but reacted on the addition of hydroperchloric acid to give [{cis-Pt(NH_3)_2}_2(μ-pyrazolato)(μ-Cl)]^<2+> as one of the intermediates and [{cis-Pt(NH_3)_2 Cl}_2(μ-pyrazolato)]^<2+> as the final product. Overall equilibrium reactions among the complexes were proposed.2 AMPZ reacts with 5'-GMP at pH 7 to give AMPZ-(GMP)_2 with Pt-N7 bonds, and its reaction is extremely slow. For example, it took about 24hr to finish the reaction at 330K when AMPZ (1x10^<-3> mol/l) was reacted with 5'-GMP (4x10^<-3> mol/l) in the phosphate buffer (1x10^<-3> mol/l, pH 7). On the other hand, CD spectra of DNA were changed at pH 7 immediately after the addition of AMPZ and the intact spectra of DNA were obtained by the addition of sodium chloride. Binding study by the equilibrium dialysis method showed that AMPZ bound to DNA was removed by the addition of sodium chloride. These two experiments show that AMPZ can bind DNA in a non-covalent fashion.3 The isomerization reaction was studied using 1H-NMR spectroscopy. When a triazolato-bridged complex was reacted with 9-ethylguanine, the Pt atom, initially bound to N2, migrates to N3 on the triazolato ring, upon reaction with N7 site of the 9-ethylguanine-.In the three novel reactions, non-covalent interaction with DNA is the most interesting, because that of several antitumor metal complexes has been recently reported. Further study is required about the relationship between non-covalent interaction with DNA and antitumor activity. Less