A series of mixed ligand platinum(II) oxadiazoline complexes bearing 7-nitro-1,3,5-triazaadamantane (7-NO2TAA) as a labile and reactive nitrogen ligand has been synthesised from easily accessible starting materials. [2+3] cycloaddition of nitrones R1R2C–N+(Me)O− to only one of the nitrile ligands in trans-[PtX2(PhCN)2] (X = Cl, Br) results in the selective formation of mono-oxadiazoline complexes trans-[PtX2(PhCN)NC(Ph)–O–N(Me)–CR1R2}] from which the remaining nitrile can be replaced by 7-NO2TAA. The resulting complexes trans-[PtX2(7-NO2TAA) NC(Ph)–O–N(Me)–CR1R2}] and their precursors were characterised by elemental analysis, IR and multinuclear NMR spectroscopy.The suitability of the target complexes as anticancer agents was extrapolated from their general chemical reactivity. They are stable in DMSO, but react with thiols and undergo aquation of a chloro ligand. In the absence of a competing ligand, the coordinated 7-NO2TAA ligand slowly hydrolyses in an aqueous medium under release of formaldehyde, and this could induce bioactivity independent of the one typically found with platinum compounds. With nitrogen heterocycles such as pyridine a slow exchange of the 7-NO2TAA ligand occurs. A combined DFT/AIM study confirms the reaction observed in the experiment and predicts that other nitrogen heterocycles such as DNA nucleobases should react in the same way. Moreover, the 7-NO2TAA should be even more labile in an aqueous medium where protonation of the remaining amines can occur. A PM6 molecular modelling study suggests that the PtCl(oxadiazoline) fragment formed after release of one chloro and the labile 7-NO2TAA ligand fits well into the DNA groove and is able to form d(GpG) intrastrand crosslinks similar to the ones observed with cisplatin.
我们用容易获得的起始材料合成了一系列混合
配体铂(II)噁二唑啉配合物,这些配合物以 7-硝基-1,3,5-三氮杂
金刚烷(7-
NO2TAA)作为易变和活性氮
配体。
硝基化合物 R1R2C-N+(Me)O- 与反式-[PtX2(PhCN)2](X = Cl、Br)中的一个腈
配体发生[2+3]环加成反应,从而选择性地形成反式-[PtX2(PhCN)NC(Ph)-O-N(Me)-CR1R2}]单噁二唑啉配合物,其中剩余的腈可以被 7-
TAA 取代。我们通过元素分析、红外光谱和多核核磁共振光谱对所得到的反式-[PtX2(7-
TAA) NC(Ph)-O-N(Me)-CR1R2}] 复合物及其前体进行了表征。它们在
二甲基亚砜中稳定,但会与
硫醇发生反应,并与
氯配体发生
水合反应。在没有竞争
配体的情况下,配位的 7-
TAA 配体会在
水介质中缓慢
水解,释放出
甲醛,从而产生与
铂化合物不同的
生物活性。在使用
吡啶等氮杂环时,7-
TAA 配体会发生缓慢的交换。DFT/AIM 联合研究证实了实验中观察到的反应,并预测 DNA 核碱基等其他氮杂环也会以同样的方式发生反应。此外,7-
TAA 在
水介质中应更具易变性,因为在
水介质中剩余的胺会发生质子化反应。PM6 分子建模研究表明,释放一个
氯和易变的 7-
TAA 配体后形成的 PtCl(恶二唑啉)片段能很好地与 DNA 沟配合,并能形成与
顺铂类似的 d(GpG) 链内交联。