Basic Research for the Creation of Artificial Nucleic Acids and Related Biomolecules with Useful Functions

Hayakawa开发了使用酸/唑复合物作为启动子通过亚磷酰胺方法高效固相合成DNA和RNA寡聚体。他还发明了一种新的亚磷酰胺方法，用分子筛作为水分清除剂，允许通过使用化学计量的起始材料和促进剂来液相制备短寡核苷酸。这些新方法允许高效合成具有生物吸引力/重要的物质，如CMP-Neu 5Ac、2-5A核心、c（GpGp）、DNA-肽缀合物和具有S-乙酰基-2-硫代乙基三酯骨架的寡脱氧核糖核苷酸。Makino致力于阐明未解决的核酸结构及其与生物功能的相关性。他（1）建立了一氧化氮对所有碱基损伤的完整机制及其与癌症和细胞死亡的相关性，（2）发现了人类端粒中C-重复序列i-基序的多种异构结构，并提出了其与癌症和细胞死亡的关系，（3）阐明了硫代磷酸酯反义物的手性与其靶DNA和RNA识别能力之间的关系，（4）提出了一种新的基于给定碱基序列的肽库构建方法。Sekine发现，在H-膦酸酯方法中，由于生长链的5 '-末端羟基对最接近的核苷酸间磷酰基的分子内攻击，发生了与寡核苷酸合成相关的严重副反应。基于这一发现，已经开发了使用活性酯中间体的改进的H-膦酸酯方法。本文还探索了“质子阻断法”作为一种无需碱基保护和后处理的DNA片段合成新策略。该策略被用于N-酰化DNA片段的创新途径，已被证明具有足够的碱基配对能力。

Hayakawa has developed efficient solid-phase synthesis of DNA and RNA oligomers via the phosphoramidite method using an acid/azole complex as the promoter. He has also invented a novel phosphoramidite method with molecular sieves as a moisture scavenger, allowing the solution-phase preparation of short oligonucleotides by the use of stoichiometric amounts of starting materials and a promoter. These new approaches have allowed highly efficient synthesis of biologically attractive/important substances such as CMP-Neu5Ac, 2-5A core, c(GpGp), DNA-peptide conjugates, and oligodeoxyribonucleotides with S-acetyl-2-thioethyl triester backbone. Makino has studied to elucidate unsolved nucleic acids structures and its relevance to biological functions. He (1) has established complete mechanisms for all the base damage by nitric oxide and their relevance to cancer and cell death, (2) has found varied isomeric structures of i-motif of C-repeat in human telomere and suggested its relationship with cancer and cell death, (3) has elucidated the relationship between the chirality in phosphorothioate antisenses and their target DNA and RNA recognition ability, and (4) has developed the novel method for peptide library for given base sequences. Sekine has found that a serious side reaction associated with oligonucleotide synthesis in the H-phosphonate approach occurs owing to an intramolecular attack of the 5'-terminal hydroxyl group of the growing chain on the closest internucleotidic phosphoryl group. Based on this finding, an improved H-phosphonate approach using active ester intermediates has been developed. The "proton-block method" as a new strategy for the synthesis of DNA fragments without base protection and post-treatment has been also explored. This strategy was utilized for an innovative route to N-acylated DNA fragments which have proved to have sufficient base-pairing ability.