2-Aminoisobutyric acid (Aib) is an essential amino acid, leading to the formation of peptAibols as microbiologically active peptides and proteins. We here report on the ring-opening polymerization (ROP) of Aib-NCA (N-carboxy-anhydrides), enabling to prepare distinct Aib-polymers up to molecular weights of 1400 g/mol with precise end-group control. ROP of Aib-NCA was accomplished via various amine initiators in frozen and liquid solvent systems, in all cases revealing the desired structures as detected by MALDI-TOF-MS and ¹H NMR. We can prove living polymerization behavior until the limit of solubility via inline-IR spectroscopy in both solution and solid state polymerization, characterizing the final polymers via MALDI-TOF-analysis. The attachment of chiral (d or l)-amino acids onto the polymer’ headgroup allows to systematically investigate the helical screw-sense of poly(Aib)_n, resulting in chiral induction to form either left (M)- or right (P)-handed screw-senses, depending on the chirality of the attached amino acid. The approach is extended toward a switchable, chiral azo-headgroup, able to change chirality of the attached poly(Aib)_n via a light-induced trigger, revealing a thermally stable cis-isomer when polymer units are attached. In contrast to many other amino acids easily polymerized into poly(amino-acids) via ring-opening polymerization (ROP) of their respective N-carboxyanhydrides (NCAs), the ROP of Aib-NCA (N-carboxy-anhydrides) here is novel and opens a general approach toward chiral, end group-modified helices with a defined screw-sense.

中文翻译：

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Aib 聚合物中螺旋方向的手性控制：氨基酸功能化聚合物的合成和螺旋度

2-氨基异丁酸 (Aib) 是一种必需氨基酸，可导致形成 peptAibols 作为微生物活性肽和蛋白质。我们在此报告了 Aib-NCA（N-羧基酸酐）的开环聚合（ROP），能够通过精确的端基控制制备分子量高达 1400 g/mol 的不同 Aib 聚合物。Aib-NCA 的 ROP 是通过冷冻和液体溶剂系统中的各种胺引发剂完成的，在所有情况下，通过 MALDI-TOF-MS 和¹ H NMR 检测到所需的结构。我们可以通过在线红外光谱在溶液和固态聚合中证明活性聚合行为直到溶解度极限，通过 MALDI-TOF 分析表征最终聚合物。手性 ( d或l)-氨基酸在聚合物的头基上允许系统地研究 poly(Aib) _n的螺旋螺旋感，从而导致手性诱导形成左手 (M)- 或右 (P)- 手螺旋感，这取决于连接氨基酸的手性。该方法扩展到可切换的手性偶氮头基，能够通过光诱导触发改变连接的聚 (Aib) _n的手性，当连接聚合物单元时显示热稳定的顺式异构体。与许多其他氨基酸相比，通过它们各自的N的开环聚合 (ROP) 容易聚合成聚（氨基酸）-羧基酸酐 (NCA)，这里 Aib-NCA (N-羧基酸酐) 的 ROP 是新颖的，并为具有确定的螺旋意义的手性端基修饰的螺旋开辟了一般方法。