5-Aminooxazole as an Internal Traceless Activator of C-Terminal Carboxylic Acid: Rapid Access to Diversely Functionalized Cyclodepsipeptides
作者:Carine Bughin、Gang Zhao、Hugues Bienaymé、Jieping Zhu
DOI:10.1002/chem.200500703
日期:2006.1.23
protonation of 5-aminooxazole leading to the electrophilic iminium salt; 2) trapping of the iminium species by the neighboring C-terminal carboxylic acid leading to a putative spirolactone; and 3) intramolecular nucleophilic addition of the tethered alcohol to the spirolactone followed by fragmentation. The strategically incorporated 5-aminooxazole serves as an internal traceless activator of the neighboring
已经开发了概念上新颖的宏观内酯化方案。它是一个多米诺骨牌过程,涉及以下序列:1)5-氨基恶唑的质子化,形成亲电亚胺盐;2)通过相邻的C-末端羧酸捕获亚胺类物质,导致推定的螺内酯;3)将栓系醇分子内亲核加成到螺内酯中,然后断裂。有策略地引入的5-氨基恶唑用作相邻的C-末端羧酸的内部无痕活化剂,因为它在环化后成为肽主链的组成部分。不需要偶联剂,在非常温和的条件下(室温下以MeCN为溶剂),仅需几当量的三氟乙酸即可触发整个序列。螺内酯作为羧酸的活化形式已通过硫迁移实验得到证实。通过与5-氨基恶唑的三组分合成相结合,从容易获得的起始原料开发了结构复杂的环二肽的两步合成方法。