Intramolecular Participation of Amino Groups in the Cleavage and Isomerization of Ribonucleoside 3′-Phosphodiesters: The Role in Stabilization of the Phosphorane Intermediate
作者:Luigi Lain、Harri Lönnberg、Tuomas Lönnberg
DOI:10.1002/chem.201301711
日期:2013.9.9
the cleavage of the 3′,5′‐phosphodiester linkage and its isomerization to a 2′,5′‐linkage are pH‐independent and 50–80 times as fast as the corresponding reactions of uridylyl‐3′,5′‐uridine (3′,5′‐UpU). The cleavage of the resulting 2′,5′‐isomer is also accelerated, albeit less than with the 3′,5′‐isomer, whereas isomerization back to the 3′,5′‐diester is not enhanced. When the amino groups are deprotonated
双核苷3',5'-磷酸二酯模型,5'-氨基-4'-氨基甲基-5'-脱氧尿苷3',5'-胸苷,在3'-的4'-位置结合了两个氨基甲基官能团已制备了连接的核苷,并在很宽的pH范围内研究了其水解反应。发现氨基官能团可加速质子化和中性形式的磷酸二酯键的裂解和异构化。当以质子化形式存在时,3',5'-磷酸二酯键的裂解及其异构化为2',5'-键是pH无关的,并且是uridylyl-3'相应反应的50-80倍,5'-尿苷(3',5'-UpU)。生成的2',5'-异构体的裂解也被加速,尽管比3',5'-异构体的裂解少,但是回到3',5'-二酯的异构化并没有增强。当氨基去质子化时 两种异构体的裂解反应仍然与pH无关,并且比UpU与pH无关的裂解快了1000倍。有趣的是,现在2'至3'异构化比其逆反应快得多。讨论了这些反应的机理。速率加速很大程度上是由质子化的氨基与磷烷中间体的静电和氢键相互作用引起的。