Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland.
J Org Chem. 2010 Feb 5;75(3):621-6. doi: 10.1021/jo902136k.
Two highly fluorescent, thermally stable diastereomeric photoadducts, 3a,b, are formed when either 5-chloro-4-thiouridine, 1, or 5-fluoro-4-thiouridine, 2, are photoexcited with 366 nm UV light in the presence of thymidine (T). 5-Fluoro-4-thiouridine, 2, exhibits photoreactivity much higher than that of the 5-chloro derivative 1. In both cases the photoreaction is very clean, leading to highly eficient conversion of the 5-halogeno-4-thiouridine (1, 2) and T to photoadducts 3a,b. The identity and structure of 3a was confirmed using mass spectrometry and 2-D NMR. The epimeric relationship of 3a,b was established by UV circular dichroism spectroscopy. The geometry of the fluorescent photoadduct is consistent with formation of an interstrand cross-link in a DNA duplex if 1 or 2 is flanked by T in an opposite strand.
当 5-氯-4-硫尿嘧啶 1 或 5-氟-4-硫尿嘧啶 2 在胸腺嘧啶 (T) 的存在下用 366nm 的紫外光激发时，会形成两种高度荧光、热稳定的非对映体光加合物 3a,b。5-氟-4-硫尿嘧啶 2 的光反应活性比 5-氯代物 1 高得多。在这两种情况下，光反应都非常干净，导致 5-卤代-4-硫尿嘧啶 (1,2) 和 T 高效转化为光加合物 3a,b。通过质谱和 2D NMR 确认了 3a 的结构和结构。通过紫外圆二色光谱确定了 3a,b 的差向异构关系。如果 1 或 2 在相反的链中被 T 侧翼包围，荧光光加合物的几何形状与 DNA 双链中形成链间交联一致。
