'Synthsis of nucleoside antiviotics and design of reptide nucleic arids that rlcognize DNA

Blasticidin S是从异色链霉菌（Streptomyces）中分离出来的，在日本曾作为杀菌剂用于防治新叶瘟。在结构上，胞嘧啶是一种特殊的核苷，具有3个氨基酸的功能，这一结构特征启发我们提出了一种基于肽主链的新型dna类似物（肽核苷，PNA）。基于这一目的，我们将重点放在了杀胚素的合成上，从手性羧酸开始，用9个步骤合成了boc保护的杀胚素酸；通过氰酸酯到异氰酸酯的重排，成功地构建了胞嘧啶的不饱和氨基糖片段；从2-乙酰氧基- n- o-乙酰- d -葡聚糖开始，用13个步骤合成了完全保护的胞嘧啶衍生物。我们实验室正在进一步研究杀母素S的全合成。

Blasticidin S was isolated from Streptomyces gmeochromogenes and at one time was used as a fungicide for the Prevention of nee blast in Japan. Careful acid hydrolysis of blasticidin S yielded blastidic acid and cytosinine Structurally, cytosinine is charactenzed as a peculiar nucleoside possessing (3-amino acid functionality ; and this structural feature inspired us to propose a new type of DNA-analogue based on a peptide backbone (peptidenucleoside, PNA). With this end in mind, we here focused our attention on'the synthesis of blasticidin S.The synthesis of Boc-protected blastidic acid was achieved in 9 steps starting from chiral carboxylic acid AIM cyanate-to-isocyanate rearrangement has been successfully employed for the construction of an unsaturated amino sugar moiety of cytosmme, and our synthesis of the fully protected cytosinine derivative required 13 steps starting from 2-acetoxy-tn-O-acetyl-D-glucal. Further studies toward the total synthesis of blasticidin S are now underway in our laboratory.