Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan.
J Am Chem Soc. 2012 May 2;134(17):7250-3. doi: 10.1021/ja301430h. Epub 2012 Apr 24.
Optically active amidine dimer strands having a variety of chiral and achiral linkers with 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 the amidine residues along with the rigidity and/or chirality of the linkers in the templates. NMR and kinetic studies reveal that the present imine-bond formation involves a two-step reversible reaction. The second step involves formation of a preferred-handed complementary double helix assisted by the chiral amidine templates and determines the overall reaction rate and diastereoselectivity of the amine.
具有各种手性和非手性连接基的光学活性脒二聚体链被合成，并用作模板，用于具有末端醛基的两个非手性羧酸单体与外消旋 1,2-环己二胺之间的非对映选择性亚胺键形成，形成由互补盐桥稳定的优选手性双链。手性脒残基的手性以及模板中连接基的刚性和/或手性显著影响外消旋胺的非对映选择性。NMR 和动力学研究表明，目前的亚胺键形成涉及两步可逆反应。第二步涉及在手性脒模板的辅助下形成优选手性的互补双链，这决定了胺的整体反应速率和非对映选择性。
