Diastereoselective Imine-Bond Formation through Complementary Double-Helix Formation
作者:Hidekazu Yamada、Yoshio Furusho、Eiji Yashima
DOI:10.1021/ja301430h
日期:2012.5.2
different stereostructures are synthesized and used as templates for diastereoselective imine-bond formations between two achiral carboxylic acid monomers bearing a terminal aldehyde group and racemic 1,2-cyclohexanediamine, resulting in a preferred-handed double helix stabilized by complementary salt bridges. The diastereoselectivity of the racemic amine is significantly affected by the chirality of
Two novel chiral dimer and trimer strands composed of m‐terphenyl groups linked through p‐diethynylbenzene units with the chiral amidine group and achiral piperazine group introduced at the terminus or center of the strands, respectively, and its complementary achiral carboxylic acid dimer and trimer were synthesized. The complementary chiral/achiral strands form an excess‐handed double‐helical structure
Chiral Template-Directed Regio-, Diastereo-, and Enantioselective Photodimerization of an Anthracene Derivative Assisted by Complementary Amidinium–Carboxylate Salt Bridge Formation
-50 °C. Temperature-dependent inversion of the chirality of the anti-HH dimer was observed when the chiral phenylene-linked amidine dimer was used and the product ee was changed from 22% at 50 °C to -86% at -50 °C. A similar enhancement of the enantioselectivity of the anti-HH dimer was also observed for the chiral amide-linked template, producing the anti-HH dimer with up to -88% ee at -50 °C. The
合成了一系列光学活性脒二聚体,由间三联苯骨架通过各种接头(例如非手性和手性对亚苯基和手性酰胺接头)连接而成,并用作区域-(头对尾( HT) 或头对头 (HH))、非对映-(反或顺)和对映选择性 [4 + 4] 光环二聚反应的非手性间三联苯羧酸单体在一端带有前手性 2-取代蒽(1) 通过互补的脒-羧酸盐桥。通过对亚苯基键连接的脒二聚体在 25°C 时几乎完全提供手性顺式 HT 和抗 HH 二聚体,而通过酰胺接头连接的那些产生所有四种二聚体。对亚苯基连接的模板倾向于在高温下促进顺式-HT-光二聚体的形成,而产物对映体过量(ee)没有显着变化,而反-HH-光二聚体的形成随着温度的降低而显着增加,伴随着产品 ee 在 -50 °C 下显着提高至 -86%。当使用手性亚苯基连接的脒二聚体并且产物 ee 从 50 °C 下的 22% 变为 -50 °C 下的 -86% 时,观察到抗 HH 二聚体手性的
Synthesis of Complementary Double-Stranded Helical Oligomers through Chiral and Achiral Amidinium−Carboxylate Salt Bridges and Chiral Amplification in Their Double-Helix Formation
acetylide complex regions, indicating that the chiral substituents on the amidine units biased a helical sense preference. The Cotton effect patterns and intensities were highly dependent on the molecular lengths. The complementary double-helix formation was also explored using the chiral/achiral amidine strands with different sequences in which a chiral amidine unit was introduced at the center (center-chiral)
A photoresponsive single-handed double helical supramolecule composed of complementary strands bearing azobenzene moieties underwent a reversible trans–cis-isomerization regulated by photoirradiation, resulting in a change in its molecular length.