Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
Nat Commun. 2019 Sep 4;10(1):3976. doi: 10.1038/s41467-019-11840-3.
Although chirality has been recognized as an essential entity for life, it still remains a big mystery how the homochirality in nature emerged in essential biomolecules. Certain achiral motifs are known to assemble into chiral nanostructures. In rare cases, their absolute geometries are enantiomerically biased by mirror symmetry breaking. Here we report the first example of asymmetric catalysis by using a mirror symmetry-broken helical nanoribbon as the ligand. We obtain this helical nanoribbon from a benzoic acid appended achiral benzene-1,3,5-tricarboxamide by its helical supramolecular assembly and employ it for the Cu-catalyzed Diels-Alder reaction. By thorough optimization of the reaction (conversion: > 99%, turnover number: ~90), the enantiomeric excess eventually reaches 46% (major/minor enantiomers = 73/27). We also confirm that the helical nanoribbon indeed carries helically twisted binding sites for Cu. Our achievement may provide the fundamental breakthrough for producing optically active molecules from a mixture of totally achiral motifs.
尽管手性已被认为是生命的基本实体，但自然界中手性物质在基本生物分子中是如何出现的仍然是一个很大的谜。已知某些非手性基序会组装成手性纳米结构。在极少数情况下，它们的绝对几何形状会被镜像对称破坏所偏向对映异构体。在这里，我们报告了首例使用打破镜像对称的螺旋纳米带作为配体的不对称催化的例子。我们通过苯甲酸附加的非手性苯-1,3,5-三羧酸酰胺的螺旋超分子组装获得了这种螺旋纳米带，并将其用于铜催化的 Diels-Alder 反应。通过对反应的彻底优化（转化率：>99%，周转数：~90），对映体过量最终达到 46%（主要/次要对映异构体=73/27）。我们还证实，螺旋纳米带确实为 Cu 提供了螺旋扭曲的结合位点。我们的成就可能为从完全非手性基序的混合物中生产光学活性分子提供了基础突破。
