Development of Synthetic Methods for N-Labeled Nucleosides to Elucidate the Structural Recognition Ability of Nucleic Acids

采用^<15>N原子区域选择性标记的寡核苷酸核磁共振研究提供了有关核酸结构、核酸与药物结合以及核苷酸与蛋白质相互作用的宝贵信息。^<15> n标记的寡核苷酸的潜在效用已经引起了人们对开发所需的^<15> n标记核苷的合成途径的极大兴趣。腺嘌呤环的n_1 -和N^6位置或胞嘧啶环的n_3 -和N^4位置是^<15>N标记的良好候选者，因为它们可以与核酸、药物和蛋白质中合适的供体或受体形成氢键。在此基础上，我们提出了一种在温和条件下用过硫酸氢铵氧化N^6-苄基腺苷和N^4-苄基胞苷脱苄的新方法。本方法基于核苷正离子自由基的化学反应性，提供了从肌苷或尿苷中分离[1-和6-^<15>N]标记的腺苷或[3-和4-^<15>N]标记的胞苷的简单而高产的方法，而不需要糖部分羟基的保护。

NMR studies employing oligonucleotides regio-selectively labeled with ^<15>N atom provide valuable information regarding nucleic acid structures, nucleic acids binding with drugs, and nucleotide-protein interactions. The potential utility of the ^<15>N-labeled oligonucleotides has led to the considerable interest in the development of synthetic routes to the required ^<15>N-labeled nucleosides. The N_1-and N^6-positions of the adenine ring or N_3-and N^4-positions of the cytosine ring are good candidates for the ^<15>N-labeling, because they can form bydrogen bonds with suitable donors or acceptors in the nucleic acids, drugs, and proteins. On this line, we have developed a newly devised method for the debenzylation of N^6-benzyladenosine and N^4-benzylcytidine which involves oxidation with ammonium peroxydisulfate under mild conditions. The present method is based on the chemical reactivities of cation radical species of the nucleosides and provides simple and high-yield procedures for the [1-and 6-^<15>N] -labeled adenosines or [3-and 4-^<15>N] -labeled cytidines from inosines or uridines without protection of hydroxyl groups in the sugar moiety.