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

杀菌素S是从产色链霉菌中分离到的一种杀菌剂，曾在日本用于防治稻瘟病。S对杀菌素进行了细致的酸解，在结构上产生了布拉西迪酸和胞嘧啶，胞嘧啶被认为是一种具有3-氨基酸功能的特殊核苷，这种结构特征启发我们提出了一种新型的基于肽骨架的脱氧核糖核酸类似物(肽核苷，PNA)。基于此，我们将注意力集中在杀菌素S的合成上。以手性羧酸为原料，经9步反应合成了BOC保护的杀菌素S。目的通过氰酸酯到异氰酸酯的重排反应成功地构建了胞质的不饱和氨基糖部分，合成了完全保护的胞嘧啶衍生物，从2-乙酰氧基-tn-O-乙酰-D-葡萄糖醛开始，共需13步。杀菌素S全合成的进一步研究目前正在我室进行。

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.