On-Resin Carboxy Group Activation of ω-Amino Acids in Solid-Phase Synthesis of Philanthotoxin Analogues
作者:Henrik Franzyk、Malene Jørgensen、Jerzy Jaroszewski、Matthias Witt
DOI:10.1055/s-2005-872118
日期:——
A protocol for parallel solid-phase synthesis of Ï-amino acid-elongated philanthotoxins was developed for exploration of structure-activity relationships for unnatural wasp toxin analogues. Several methods for on-resin activation of N-trityl-linked Ï-amino acids were investigated, and the influence of chain length upon activation as pentafluorophenyl (Pfp) esters was examined. Comparison of Pfp-ester activation with phosphonium- and aminium/uronium-promoted coupling without pre-activation of the resin-bound carboxylic acids showed that only benzotriazol-1-yloxytris(pyrrolidino)phosphonium hexafluorophosphate (PyBOP) exhibited a comparable efficiency. The present Pfp ester protocol gave high yields and purities of the resulting philanthotoxin analogues; however, in the case of γ-aminobutyric acid (GABA), use of PyBOP was required in order to avoid lactamization to 2-pyrrolidone.
开发了α-氨基酸延长的花椒毒素的平行固相合成方案,用于探索非天然黄蜂毒素类似物的结构-活性关系。研究了几种 N-三苯甲基连接的 α-氨基酸的树脂上活化方法,并检查了链长对五氟苯基 (Pfp) 酯活化的影响。在未预活化树脂结合的羧酸的情况下,将 Pfp-酯活化与鏻和铵/脲促进的偶联进行比较表明,只有苯并三唑-1-基氧基三(吡咯烷)鏻六氟磷酸盐 (PyBOP) 表现出相当的效率。目前的 Pfp 酯方案得到了高产率和高纯度的花椒毒素类似物;然而,对于γ-氨基丁酸(GABA),需要使用PyBOP以避免内酰胺化为2-吡咯烷酮。