Investigation of 'Head-to-Tail'-Connected Oligoaryl N,O-Ligands as Recognition Motifs for Cancer-Relevant G-Quadruplexes
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
... 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 (K D = 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.