Pithan Phil M, Kuhlmann Christopher, Engelhard Carsten, Ihmels Heiko
Department of Chemistry and Biology, and Center of Micro- and Nanochemistry and Engineering, University of Siegen, Adolf-Reichwein-Str. 2, 57068, Siegen, Germany.
Chemistry. 2019 Dec 13;25(70):16088-16098. doi: 10.1002/chem.201903657. Epub 2019 Nov 8.
A series of new 5-mono- and 5,5'-bisamino-substituted azothiazole derivatives was synthesized from the readily available diethyl azothiazole-4,4'-dicarboxylate. This reaction most likely comprises an initial Michael-type addition by the respective primary alkyl and aromatic amines at the carbon atom C5 of the substrate. Subsequently, the resulting intermediates are readily oxidized by molecular oxygen to afford the amino-substituted azothiazole derivatives. The latter exhibit remarkably red-shifted absorption bands (λ =507-661 nm) with high molar extinction coefficients and show a strong positive solvatochromism. As revealed by spectrometric titrations and circular and linear dichroism studies, the water-soluble, bis-(dimethylaminopropylamino)-substituted azo dye associates with duplex DNA by formation of aggregates along the phosphate backbone at high ligand-DNA ratios (LDR) and by intercalation at low LDR, which also leads to a significant increase of the otherwise low emission intensity at 671 nm.
一系列新的5-单氨基和5,5'-双氨基取代的偶氮噻唑衍生物由易于获得的偶氮噻唑-4,4'-二羧酸二乙酯合成。该反应很可能首先由相应的伯烷基胺和芳胺在底物的C5碳原子上进行迈克尔型加成。随后，生成的中间体很容易被分子氧氧化，得到氨基取代的偶氮噻唑衍生物。后者表现出显著红移的吸收带（λ = 507 - 661 nm），具有高摩尔消光系数，并表现出强烈的正溶剂化显色性。光谱滴定以及圆二色和线性二色性研究表明，水溶性的双（二甲基氨基丙基氨基）取代偶氮染料在高配体- DNA比例（LDR）下通过沿磷酸骨架形成聚集体与双链DNA结合，在低LDR下通过嵌入结合，这也导致原本在671 nm处较低的发射强度显著增加。
