We report the facile synthesis of sequence-defined, uniform oligo(ester-amide-ester)s, and periodic poly(ester-amide-ester)s composed of ɑ-hydroxy acids and ɑ-amino acids. The synthetic strategy for preparing the oligomers involves two sequential steps with bromoacetic acid and potassium isocyanoacetate as the key building blocks. (1) The first step is a nucleophilic substitution reaction between a bromoacetic ester and potassium isocyanoacetate to generate a new isocyanoacetic ester, (2) and the second is a Passerini reaction of the formed isocyanoacetic ester with an aldehyde and bromoacetic acid to form a longer bromoacetic ester with an ester-amide linkage and a side-group originating from the aldehyde. Repeating this cycle affords sequence-defined uniform oligo(ester-amide-ester)s with different side groups. This strategy efficiently provides uniform, symmetrical oligo(ester-amide-ester)s via an iterative approach. Furthermore, two strategies were examined to obtain sequence-defined periodic poly(ester-amide-ester)s through the polycondensation of different oligomers. The polycondensation based on the nucleophilic substitution of α,ω-bromo carboxylic acids as the oligomer was less effective, while the DIC/DPTS-mediated polycondensation of α,ω-hydroxy carboxylic acids as the sequence-defined oligomer was efficient enough to afford high-molecular-weight periodic poly(ester-amide-ester)s. An efficient and straightforward strategy for the synthesis of uniform, sequence-defined oligo(ester-amide-ester)s via sequential nucleophilic substitution reactions and Passerini reaction was developed. The side groups could be easily regulated by the Passerini reaction of different aldehydes. The synthesis of uniform, symmetrical, long-chain oligomers was further demonstrated by an iterative approach. The DIC/DPTS-mediated polycondensation of the α,ω-hydroxy carboxylic acids as the sequence-defined oligomer afforded high-molecular-weight periodic poly(ester-amide-ester)s. The thermal properties of these oligo/poly(ester-amide-ester)s were also examined.

中文翻译：

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通过正交亲核取代反应和 Passerini 反应确定序列定义的寡聚物/聚（酯-酰胺-酯）

我们报告了由 ɑ-羟基酸和 ɑ-氨基酸组成的序列定义的、均匀的低聚（酯-酰胺-酯）和周期性聚（酯-酰胺-酯）的简便合成。制备低聚物的合成策略包括两个连续步骤，其中溴乙酸和异氰乙酸钾作为关键构建块。(1) 第一步是溴乙酸酯与异氰乙酸钾之间的亲核取代反应生成新的异氰乙酸酯，(2) 第二步是所形成的异氰乙酸酯与醛和溴乙酸的 Passerini 反应，形成更长的异氰乙酸酯。具有酯-酰胺键和源自醛的侧基的溴乙酸酯。重复此循环可提供具有不同侧基的序列定义的均匀低聚（酯-酰胺-酯）。该策略通过迭代方法有效地提供了均匀、对称的低聚（酯-酰胺-酯）。此外，研究了两种策略，通过不同低聚物的缩聚来获得序列定义的周期性聚（酯 - 酰胺 - 酯）。基于 α,ω-溴羧酸作为低聚物的亲核取代的缩聚效果较差，而 DIC/DPTS 介导的 α,ω-羟基羧酸作为序列定义的低聚物的缩聚反应足以提供高-分子量周期性聚（酯-酰胺-酯）。开发了一种有效且直接的策略，用于通过顺序亲核取代反应和 Passerini 反应合成均匀的、序列定义的低聚（酯 - 酰胺 - 酯）。侧基可以很容易地通过不同醛的 Passerini 反应进行调节。通过迭代方法进一步证明了均匀、对称、长链低聚物的合成。DIC/DPTS 介导的 α,ω-羟基羧酸缩聚作为序列定义的低聚物提供了高分子量的周期性聚（酯-酰胺-酯）。还检查了这些低聚物/聚（酯-酰胺-酯）的热性能。