Oligomeric compounds, constituted of consecutive N,O-heteroaromatic rings, introduce useful and tunable properties as alternative ligands for biomolecular recognition. In this study, we have explored a synthetic scheme relying on Van Leusen oxazole formation, in conjunction with C–H activation of the formed oxazoles and their subsequent C–C cross-coupling to 2-bromopyridines in order to assemble a library of variable-length, ‘head-to-tail’-connected, pyridyl-oxazole ligands. Through investigation of the interaction of the three longer ligands (5-mer, 6-mer, 7-mer) with cancer-relevant G-quadruplex structures (human telomeric/22AG and c-Myc oncogene promoter/Myc2345-Pu22), the asymmetric pyridyl-oxazole motif has been demonstrated to be a prominent recognition element for G-quadruplexes. Fluorescence titrations reveal excellent binding affinities of the 7-mer and 6-mer for a Na+-induced antiparallel 22AG G-quadruplex (KD = 0.6 × 10−7 M−1 and 0.8 × 10−7 M−1, respectively), and satisfactory (albeit lower) affinities for the 22AG/K+ and Myc2345-Pu22/K+ G-quadruplexes. All ligands tested exhibit substantial selectivity for G-quadruplex versus duplex (ds26) DNA, as evidenced by competitive Förster resonance energy transfer (FRET) melting assays. Additionally, the 7-mer and 6-mer are capable of promoting a sharp morphology transition of 22AG/K+ G-quadruplex.
寡聚化合物,由连续的N,O-杂环芳香环构成,作为生物分子识别的替代配体,引入了有用且可调节的特性。在这项研究中,我们探索了一种合成方案,依赖于Van Leusen噁唑的形成,结合形成的噁唑的C-H活化以及它们随后与2-溴吡啶的C-C交叉偶联,以组装一个可变长度、'头对尾'连接的吡啶-噁唑配体库。通过研究三种较长配体(5-聚体、6-聚体、7-聚体)与癌症相关的G-四链体结构(人类端粒/22AG和c-Myc致癌基因启动子/Myc2345-Pu22)的相互作用,已经证明了不对称的吡啶-噁唑基团是G-四链体的一个显著识别元素。荧光滴定显示,7-聚体和6-聚体对Na+-诱导的反平行22AG G-四链体具有优异的结合亲和力(分别为KD = 0.6 × 10−7 M−1和0.8 × 10−7 M−1),对22AG/K+和Myc2345-Pu22/K+ G-四链体具有令人满意(尽管较低)的结合亲和力。所有经过测试的配体在竞争性Förster共振能量转移(FRET)熔融实验中表现出对G-四链体与双链(ds26)DNA的显著选择性。此外,7-聚体和6-聚体能够促进22AG/K+ G-四链体的形态急剧转变。