To explore the role of proline amide moieties in polymer-supported organocatalysts, side-chain l-proline–l-alanine (Pro-Ala) dipeptide-containing block copolymers were synthesized, and their catalytic potential for the aldol reaction was explored. The dipeptide monomer (Boc-Pro-Ala-HEMA) was polymerized to prepare block copolymers in the presence of hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA) and hydrophobic poly(methyl methacrylate) (PMMA) macro-chain transfer agents. Boc group expulsion from the block copolymers produced double hydrophilic PPEGMA-b-P(Pro-Ala-HEMA) (1b) and amphiphilic PMMA-b-P(Pro-Ala-HEMA) (1c) polymers. The solution behaviors of the polymers were studied by various physical techniques, which showed the formation of self-assembled aggregates of 1c in water and N,N-dimethylformamide (DMF)/water solvent mixtures. These polymers are used as organocatalysts during the aldol reaction of cyclohexanone and 4-nitrobenzaldehyde in different solvent polarities, catalyst loadings, temperatures, and reaction times. This work emphasizes superior catalytic activity of 1c at lower catalyst loadings (5%) while maintaining high conversion (95%) and enantioselectivity (94%) across multiple recycling cycles in DMF/water at a 3:1 ratio (v/v).

中文翻译：

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侧链二肽悬垂聚合物自组装催化的不对称羟醛反应


为了探索脯氨酸酰胺部分在聚合物支持的有机催化剂中的作用，合成了含有侧链L-脯氨酸-L-丙氨酸（Pro-Ala）二肽的嵌段共聚物，并探索了它们对羟醛反应的催化潜力。在亲水性聚(聚(乙二醇)甲醚甲基丙烯酸酯)(PPEGMA)和疏水性聚(甲基丙烯酸甲酯)(PMMA)大链存在下聚合二肽单体(Boc-Pro-Ala-HEMA)制备嵌段共聚物转让代理。 Boc基团从嵌段共聚物中排出，产生双亲水性PPEGMA-b-P(Pro-Ala-HEMA) (1b)和两亲性PMMA-b-P(Pro-Ala-HEMA) (1c)聚合物。通过各种物理技术研究了聚合物的溶液行为，结果表明1c在水和N,N-二甲基甲酰胺（DMF）/水溶剂混合物中形成自组装聚集体。这些聚合物在环己酮和4-硝基苯甲醛在不同溶剂极性、催化剂负载量、温度和反应时间的羟醛反应过程中用作有机催化剂。这项工作强调了 1c 在较低催化剂负载量 (5%) 下的优异催化活性，同时在比例为 3:1 (v/v) 的 DMF/水中的多个回收循环中保持高转化率 (95%) 和对映选择性 (94%)。